A Super Simple Salad in Stor(age): A DIY Home Hydroponics Example

Say the word “hydroponics” or the even more mysterious sounding “controlled environment agriculture” and the image that most people conjure in their minds is of large greenhouses or artificially lit rooms filled with complex hoses and tubes using all manner of technological gizmos to pump water and nutrients to plants.  True, modern ag technology does allow for some pretty amazing and technical production of food but hydroponics can be super simple and so easy that just about any home gardener can do it. 

Why grow hydroponically at home?

Growing vegetables can be pretty easy and straightforward for outdoor production – seeds, soil, water, and wait (sure, there’s a few other steps in there), so why complicate things by growing hydroponically?  Aside from the challenge and the novelty that delights many gardeners, intensive growing with hydroponics can allow gardeners with the smallest of spaces to grow impressive amounts of produce in a short amount of time.  Most of these systems also do well for winter production indoors with the use of grow lights or some good-sized south facing windows.

Hydroponic or similar-type production systems are the “craze” right now for folks wanting to grow some of their own produce at home, usually in smaller indoor spaces, but these systems can run into the hundreds or thousands of dollars making production less than economical.  Plus, most of these systems require the use of pre-made plant/seed plugs that add to the expense.

Why is hydroponic production important?

On a larger scale, hydroponic and controlled environment agriculture has a few benefits that will help in feeding a growing population on a warming planet.  Hydroponic production can be pretty intensive, meaning that it can grow a large amount of food in a relatively small amount of space.  This makes it ideal for production in urban areas, which is important as most countries become more urbanized.  It also cuts down on transportation needs to get food to consumers. This not only reduces fuel consumption but also, as we can see, makes it easier to get food to large populations when distribution becomes an issue.  And as the term “controlled environment agriculture” implies crops can be grown using hydroponics in greenhouses or indoor farms no matter what the season or climate making it ideal for year-round production in areas where it is too cold or too hot part of the year to do so.  This also means that hydroponics and controlled environment agriculture can be important mitigation strategies for climate change. When the temperatures or precipitation are no longer favorable for growing outdoor crops in certain areas, controlled environment ag can provide a stable source of produce with indoor production. 

And as ironic as it sounds, growing hydroponically drastically reduces the amount of water used for production.  Closed systems, which either recirculate water or grow in enclosed containers, use much less water than field production systems relying on irrigation.

A simple system example

Earlier this year I build some super simple enclosed hydroponic systems for demonstration at our Extension office and at the county fair.  My goal was to show how easy hydroponic production can be – no need for pumps, tubes, or expensive equipment.  The system was so simple that I built it with my non-horticultural interns as an onboarding/team building exercise. 

The system we built utilizes the Kratky method of hydroponic production – a simple system where the plant is suspended on top of a container full of nutrient solution.  In a typical recirculating hydroponic system where water is moved around air is introduced into the water that then provides oxygen to the roots to avoid hypoxic conditions that damage roots.  Some static systems rely on introducing air (like using aquarium air stones) to introduce oxygen but the Kratky method is even simpler than that.  Instead of introducing air into the solution, the level of the solution is reduced (usually through use and evaporation) as the roots grow keeping a section of roots exposed to open air.  The setup is super simple and low maintenance – no moving parts, no electricity (unless I need to use lights for indoors). Just plants, a medium to hold them, a container and a nutrient solution.

How To Start Growing With The Kratky Method - Upstart University
The Kratky Method, Source

I’ve seen the systems made with all kinds of containers but we chose 25 gallon storage totes because they are inexpensive and pretty easy to come by.  Having a lid that is relatively easy to cut/drill also makes these kinds of containers ideal to make multi-plant “beds” but I’ve also seen lidded buckets used as a single-plant system. 

To hold the plants we used plastic net pots that you can find at garden centers that sell pond or aquarium plants (or order) that are also now common at hydroponic supply stores, if you’re lucky enough to have one in town.  You can also use plastic orchid pots or standard nursery pots, perhaps adding extra holes for roots to grow out.  We used 6 inch and 2 inch pots to plant a variety of sizes.

Net pots in the system, with holes made slightly smaller for them to fit and not fall in.

Next we cut holes in the lid slightly smaller than the diameter of the pots so that they sit on top and don’t fall through.  You can do this by tracing and cutting with a sharp object, or use a drywall hole saw that you use with a drill to cut a perfectly round hole. We used one with adjustable sizes, rather than buying individual sizes. 

And now, to plant!

The pots were then filled with an inert, soil-less medium to support the plants.  We used a puffed clay stone called LECA, but you can use rockwool or hemp fiber blocks made for hydroponic starts, large particle perlite, or even something like a poly fiber filling (like used in sewing) – just something that won’t break down to hold the plants in place. 

Some of the plants I had started in fiber cubes so those easily went into the LECA, but we did end up buying a few transplants.  Since these were started in some sort of potting soil we had to wash as much of the soil off as we could.  We placed larger plants like peppers and kale in the large pots and smaller plants like herbs in the small pots. 

As for plant selection, leafy greens and herbs like basil and parsley are easiest and can use smaller containers and pots. Plants like tomatoes and peppers will need bigger containers and pots and will also require more light and heat if you are growing them indoors.

A solution for easy nutrient solutions

And last but not least – the nutrient solution.  Since we are growing without soil we have to provide basically all macro and micro nutrients. We are used to supplying nutrients like nitrogen and phosphorous, but not so used to supplying things like manganese and molybdenum. This one is probably the scariest to those new to hydroponics, but there are some easy options out there for small scale production that are “off the shelf” solutions.  Rather than worry about mixing up nutrients by hand, these pre-made mixes make it easy for home growers to try hydroponics.  They come in two or three part sets of either liquid or solid fertilizers, because some of the chemicals used will react and precipitate out into a sludge if kept together in concentrated form.  Just mix according to package directions and you’re good to go.  If you are growing anything like tomatoes or peppers that require flowering and fruiting, you’ll want to make sure the formula is for flowering plants. Regular water-soluble fertilizers might do in a pinch, but for long term growth you’ll want to invest in something with all micronutrients. 

Storage tote hydroponic system, sitting in the office courtyard.

If you’re planning on refining your technique, you might want to invest in a pH meter or TDS (total dissolved solids) meter to fine tune the solution based on the minerals dissolved in your water.  And if you have really hard water you can usually get an additional nutrient product to account for the pH and calcium levels to balance things out. 

So now we just filled the totes with the solution all the way up until the bottom few inches of the pots were covered.  We kept watch on the solution and added water as needed, keeping in mind that as the roots grow out of the pot the nutrient solution level needed to be low enough to expose around 2/3 of the roots to air. 

The nutrient solution is only a few inches deep in the bottom of the tote at this time, allowing roots to be exposed to air for oxygen uptake.

As the plants grow, you’ll just want to keep an eye for signs of nutrient deficiency and add nutrients to the water as needed.  The solution should be completely dumped and replaced every 6-8 weeks, as the plants rapidly deplete some nutrients, allowing some to build up to toxic levels.  You can typically just pour the solution out on the garden or lawn, as it only contains plant nutrients. However, you’ll want to make sure not to keep dumping in the same spot to avoid build up of salts in the area. Spraying the area with a bit of water from the hose can help wash it off of plants and start diluting it into the soil, rain and weather should do the rest of the job. But if you are in an area with little precipitation, you may also want to take care since there won’t be a lot of water to dilute the nutrient build up over time. And just remember, if you harvest and completely remove crops, pull apart and clean the system with some good soapy water and a sanitizer (bleach works well).  You should do this every few months if you have a long-lived crop in the system. 

In a nutshell…..

A simple system like this one can be a great way to explore a new growing technique, even for beginner gardeners.  After these were set up, we basically left them in our courtyard all summer with little to no maintenance, except adding water earlier in the season and changing out the nutrient solution once.  If you need a bit more info, or want to try something a little more complex, there are some great resources out there for small systems that I’ll share below.   

Resources:

Growing Lettuce in Small Hydroponic Systems – Univ of FL Extension

How to grow with the Kratky Method – Upstart Farms

Small-scale hydroponics – Univ of Minn Extension

Home Hydroponics – Illinois Extension

Everything is chemicals: the myth and fear of “chemical-free” gardening

“Chemical-free” – a term I’ve seen several times attributed to many products, especially food and produce at farmers markets and even in gardening circles these days.  This term is often misused to describe plants grown without the use of any pesticide, either conventional or organic. I have my thoughts that I’ll share later on that subject but first let’s talk about this “chemical-free” that gardeners, farmers, and others use and why its not only a myth, but a dangerous one at that.

Ain’t such a thing as “chemical-free” anything

At face value, the term “chemical-free” would literally mean that whatever the label is applied to contains no chemicals.  That the entire item, whether it be animal, vegetable, or mineral is devoid of any and all chemicals.  Factually this can never, ever be true.  Everything that exists is made of chemicals.  Oxygen, water, carbon dioxide, and any simple molecule, by definition, is a chemical.  Plants and animals are organized structures filled with complex chemicals.  Even you and I, as humans, are walking, talking bags of chemicals.  The air we breathe, the food we eat, and the water we drink are all composed of a great mixture of chemicals.  The use of the term “chemical-free” to describe anything is uninformed at best, and intellectually dishonest at worst. But a bigger problem, as we’ll discuss later, is that using the term can cause confusion and even fear of things as simple as food and as complex as science and medicine. 

Expert reveals how even natural foods contain chemicals | Daily Mail Online
The “ingredient list” of a peach.
Source

What most people intend to say when they use the term “chemical-free” in relation to plants or produce is that they are produced without use of pesticides or conventional “chemical” fertilizers.  Therefore, a better term to use would be “pesticide-free” instead of “chemical-free” as it more accurately represents the situation.  Many may ask why the term “organic” or “organically grown” couldn’t also be used to describe “pesticide-free” plants.  And while those terms would be accurate, organic production can involve the use of organic pesticides that are derived from natural sources such as plants, bacteria, or natural minerals.  Natural sources of fertility for plants, such as composts and even soil itself, are all composed of a myriad of chemical substances.  Plants don’t differentiate between the chemicals they uptake from compost or soil and those from fertilizers.  To plants, nitrogen is nitrogen and phosphorous is phosphorous no matter where it comes from.

For some clarification on what different growing and production terms like these mean, check out this lecture I gave for the Oregon Farmers Market Association earlier this year.

While many have a strong opinion on the use of pesticides and fertilizers, I’ll state here that the use of any pesticide, organic or conventional, must follow the label on the container by law. And the use of any pesticide according to the label instructions means that the use of that pesticide should present a minimal risk to the health of the applicator, consumer, off-target species, and the environment.  And don’t use any home remedy recipes or products that aren’t labeled (or at least scientifically researched) for use as a pesticide.  In most cases these remedies aren’t effective, in some cases they can be more dangerous to human health or the environment than the pesticide they are trying to replace.  And applying them as a pesticide could also be illegal. 

Reading Pesticide Labels - Pests in the Urban Landscape - ANR Blogs
Pesticide label signal words that denote relative toxicity of a given pesticide.

Any gardener or producer, whether they use pesticides or not, should also be practicing Integrated Pest Management (IPM) to decrease or mitigate the effects of insect and disease pests on their plants.  For those using pesticides, use of the least toxic pesticide that offers control of the problem should be the last step in a series of steps to avoid damage from pests after a threshold of damage has been reached.  For those who don’t use pesticides, IPM should be a central practice in their gardening or farming practice.  Unfortunately, the tradeoff for not using pesticides is often time and labor, so successful “pesticide-free” growing often involves more work (and for produce at the market or grocery store, a higher price).  I have seen some gardeners and farmers who don’t use pesticides and don’t make an effort to practice IPM, taking whatever plants or produce mother nature and her children deal them.  I’ve sometimes referred to this type of growing as “organic by neglect” as I see insect and disease riddled produce harvested and even sold at local farmers markets.

Why does it matter?

“So what if I use the term ‘chemical-free’?  It doesn’t hurt anyone,” you may say.  While this may seem the case, the use of the term “chemical-free” has risen as a result of what many call chemophobia, effects that reach far beyond the garden or the farmers market.  This kind of thinking leads to the incorrect notion that all “natural” remedies are safe and all “synthetic” remedies are dangerous.  True, many chemicals do pose a risk to human, plant, animal, and environmental health but many do not.  Just like not all natural substances are safe.  Poison ivy, anthrax, botulinum, and cyanide are all natural and cause everything from a skin rash to instant death (sometimes I get poison ivy so bad I wish for instant death).

This chemophobia can lead to, or is a symptom of, a broader mistrust of science, the scientific process, and modern medicine that has developed in society in the last few decades.  Many attribute this to an anti-intellectual or anti-science stance in society resulting from mistrust or political saber-rattling against universities, education in general, science/scientists, “big Pharma”, “big Agriculture”, and others.  As a result, the news is filled with people who eschew well-researched scientific advances that have been proven safe and instead turn to home remedies that have no such guarantee of either effectiveness or safety.  The results can be worse than the effects of the proven advance the person was trying to avoid. 

While the outcomes of “chemical free” gardening might not have such dire consequences as immediate death, the misuse of such terms can feed into a cycle of anti-science cause and effect, serving as both a cause and a symptom of mistrust of science and the scientific process.  While everyone has a right to choose whether or not they use pesticides (or any other scientific advancement), making such decisions from a place of knowledge instead of fear is paramount for success and continued advancement. 

Sources and further reading:

https://www.columbiasciencereview.com/blog/debunking-the-myth-of-100-chemical-free-slogans

https://www.sciencedirect.com/science/article/pii/S0278691520302787

https://www.canr.msu.edu/news/chemophobia-fearing-chemicals

https://www.businessinsider.com/what-chemicals-are-in-an-all-natural-banana-2017-6

Counting the Days to Maturity: Calculating planting dates for fall vegetables

While most of the US is still seeing sweltering hot temps, the cool temps of fall and winter aren’t really all that far away for those of us unlucky (or lucky) enough to not live in a tropical climate.  The tomatoes, peppers, cucumbers, and other warm-season crops planted back at the beginning of summer are still puttering along, even if they might be getting a little long in the tooth and starting to look a little worse for wear ( especially if disease has ravaged them).  For those who aren’t quite done with gardening for the year or who want to reap the bounty of fall crops and get the most out of their production space, fall gardening can be a great tool to extend the garden season.  But knowing when to plant what is tricky, especially when we are talking about different weather patterns and frost dates all around the country.  So a bit of weather data, info from the seed packet or label, a touch of math, and a calendar can be great tools to figure out when you can plant no matter where you are.  Of course if you do live in one of those warmer tropical areas your planting calendar is kind of turned on its head from what us more northern gardeners face. You may prefer to time your planting to avoid high heat. 

The first thing to think about is what you can plant.  Cool-season crops such as the Cole crops (cabbage, kale, broccoli, etc.), leafy greens (lettuce, spinach, Bok choi, etc.), root crops (radishes, beets, turnips, scallions), and some cool weather loving herbs like cilantro and parsley are all par for the course for a garden going into cooler fall and winter temps.  Depending on when you have extra space in your garden to plant and how long your growing season is you can often sneak in a late planting of fast-growing warm season crops to mature before the last frost.  Beans, cucumbers, and summer squash all have varieties that are fast maturing and can be started mid-summer for an early fall harvest.  Unfortunately, as of this writing the window for those warm-season crops has passed for me, but others in warmer zones may still have time. 

One question I get asked often is whether you should start indoors or out. I always tell folks that for things normally direct-seeded, like beans or lettuce, sow as normal. For things that are normally started indoors, the choice is yours. Cole crops are started indoors in spring because they need warmer temps to germinate. Since it is hot outside, you won’t need to grow them indoors for the heat (though it may be too hot outdoors if temps are over 85). You can start them in containers in a protected area outdoors instead of trying indoors. Theoretically you could direct seed them into the garden, but management is difficult to keep them watered, weed-free, and alive out there in the cruel garden world.

To know what you can plant and when, the first bit of info you’ll need is from the seed packet or label (or do some research if you know the cultivar/variety).  You’ll want to know the “days to maturity”, which is an estimate of how long it will take to go from seed (or transplant) to edible crop.  For those warm season crops, you might want to shop around because those days to maturity can be wildly variable – you can find beans that mature in 60-65 days and some that take 100+.  You’ll want to choose faster maturing varieties. 

Assuming that you’ll want a harvest window longer than a day and given that plant growth slows down as temperature cools (respiration is temperature dependent so plant processes slow down as temperatures drop), you’ll want to add a few weeks to the maturity days to take that into account.  This should be sufficient for cool season crops that will survive well past the first frost and freeze dates.  The aim for cool season crops is to get them close to a mature size before cold weather sets in since their growth will slow down at that point.  For warm season crops you’ll want to add a little more time to provide a cushion against frost which will kill the plants.  For info on killing temperatures of certain crops, check out my previous article here

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For example, if I wanted to plant Asian Delight Bok choi (I fell in love with it when I trialed it for the All-America Selections program) I’d see on the packet that it has an average maturity time of 37 days (which is pretty damn fast).  My math would be:

37 days (to maturity) + 14 days (harvest period) + 14 days (fall factor) = 65 days

Next, you’ll need to know a bit of weather data – more specifically the expected date of your first frost/freeze.  You can find this on the website of your local National Weather Service office, or get an idea from the map below. (This data is usually updated every decade or so – you’ll want to check it every few years for updates as the dates have been changing due to climate change.) The date ranges given are usually a median, meaning that half of the frost days fall before and half fall after the given dates.  Keep that in mind – sometimes frost will come earlier or be much later.

I live in Omaha, Nebraska so our median frost date (according to the map) is Oct 10.  Now I know that I need to plant my Asian Delight Bok choi 65 days before Oct 10.  I can grab a calendar and count backward from October 10 (or I can cheat and use an online date calculator like this one) and see that the suggested planting date is August 6.  Since I missed it by a week I can decide if I want to gamble a little and still plant since I know that it could very well frost later than Oct 10 and that the Bok choi will survive much later into the season anyway.  But it gives me an idea of what to expect. 

Had I wanted to plant something like beans for a late crop, my calculation would have definitely shown me that it was too late, letting me know that I shouldn’t waste my time.  For example, Blue Lake beans take around 55-60 days to mature (almost twice as long as my Bok choi), plus I need to add that extra 14 days for the frost factor meaning that I would have had to plant 97 days before first frost, which would have been in early July for me. 

You can extend the time you have for growing fall crops by using season extension techniques like row covers, low tunnels, cloches, etc.  For row covers, the materials you buy such as the spun fabric row cover will offer a certain number of degrees of protection.  For example, a medium weight row cover might offer 8 degrees of protection, meaning it will be 8 degrees warmer under the cover than the air temp.  Keep those in mind when planning your fall garden.  Perhaps we’ll have to talk about those in another article soon. 

Sources:

Fall Gardening (Nebraska Extension)

Fall Vegetable Gardening (Virginia Cooperative Extension)

Fall Frost Info (Weather.gov)

Water: Garden Friend….and Foe? – Water, Relative Humidity, and Plant Diseases

We all know that water is essential for life and that we have to ensure our landscapes, gardens, and houseplants all have a sufficient supply of the stuff.  Forget to water your garden during a hot, dry spell and it could mean disaster for your plants.  But water can also create issues for plants, usually when it is in an overabundance – water helps spread and develop diseases on foliage and excess soil moisture can damage roots, creating opportunities for root rots and other diseases.  How do you meet the water needs of the plant while also avoiding issues associated water?  Understanding how water affects disease organisms will help, along with some tried and true Integrated Pest Management Strategies.

Water and Pathogenic Microbes

Both bacteria and fungi require water to grow and reproduce.  Most do not have a mechanism to actively take up and manage water, so they uptake water mainly through osmosis.  This means there must be some form of water present for those microbes that are actively growing and especially for processes like reproduction which use not only a lot of energy but might also be required to carry spores in order to spread.

File:Septoria lycopersici malagutii leaf spot on tomato leaf.jpg -  Wikimedia Commons
Septoria leaf spot, a common fungal disease of tomato that requires water for initiation and development.

Both pathogenic microbes and beneficial (or neutral) microbes require water to thrive.  It is one side of what we refer to as the disease triangle.  Water (along with temperature) are major components of the “favorable environment” side of the triangle, with the other sides being a plant capable of being infected and a population of pathogens capable of infecting.  Those last two sides meaning you have to have a population of the pathogen big enough to initiate or sustain an infection and a plant that can actually be infected by that pathogen.  For example – one disease spore may or may not be enough to start an infection (depending on the pathogen), but several hundreds or thousands definitely can.  And the pathogen has to be one that can actually infect the plant – it doesn’t matter if you have a million spores of Alternaria solani (one of two closely related fungi that cause early blight in tomatoes) on your cucumber plants, they likely won’t get a disease.  But if there are spores of A. cucumerina, a different species, you’ll likely get leaf spot on those cucumbers.  But it doesn’t matter if you have both a susceptible plant and a pathogen, there has to be a favorable environment (water and temperature) for there to be a disease infection. 

As this paper points out, water in the form of liquid (rain, ground water, dew, etc) and vapor (air humidity, fog) can provide the environment for microbe development in the soil and on foliage.  Microbes in the soil are ubiquitous as water is typically available in most soils (except in droughty or arid areas) , but excess soil moisture can create booms in populations for both the “good” microbes and the “bad” ones.  Microbes that live on foliage (sometimes referred to as epiphytic since they rely on moisture from the atmosphere) are much more likely to be water stressed since they are exposed to the atmosphere.  When there isn’t water available on the surface of leaves (from rain, fog, etc.) microbes tend to colonize around areas where water leaves the plant – stomata and to a lesser extent around tricomes and hairs. 

The paper also points out high atmospheric humidity is positively correlated with the number of fungi on a leaf surface. It’s also a requirement for diseases microbe spores to germinate, for filamentous fungi to break dormancy, for pathogen survival, for microbe movement on the leaf surface, and for disease infections to be sustained.  It is also shown that heavy precipitation increases water availability to these microbes thus hastening their growth.  Precipitation also dislodges and disperses pathogen spores and cells to adjacent plant tissues, and to leaves of nearby plants.  High humidity also makes leaf cuticles more permeable and promotes opening of the stomata, which can serve as an entry point for pathogenic infection.

Once inside the plant, microbes such as fungi and bacteria can thrive on the aqueous environment inside a plant, moving easily between cells or into the vascular tissue (depending on disease).  Pathogens that thrive in wet conditions, however, may initiate water soaked lesions on the plant to develop conditions favorable to their growth. 

Water, water everywhere – so is there anything you can do?

Of course, water is naturally occurring and in most places falls from the sky in some form or another.  In some places very little precipitation falls, in others there’s a lot. And don’t forget about the humidity, dew, and fog (which are often more common in places that get more rain, but provide moisture even in dry climates).  There are a few places where the atmospheric moisture levels are in that “just right” zone to support plant growth but not pathogen growth, which makes agricultural production of certain crops easier.  You could consider these areas the “Goldilocks” zone for crop production.  For example, a lot of seed crops are produced in the Midwest and arid north West, potatoes in Idaho, apples in Washington, etc.  The conditions there mean that, at least when those crops were getting established (before the advent of modern pesticides) in those regions, disease pressure was low. 

You can’t stop the rain, of course, if you’re in a place both blessed and cursed with abundant rainfall or atmospheric humidity.  But there are some things that you can do reduce the likelihood of diseases spread or supported by that water and humidity.

  • Evidence shows that there is a positive correlation between the density of planting and disease incidence.  Therefore, proper plant spacing and pruning can do at least three major things.  First, having space between plants, especially in the vegetable garden, can reduce the splashing of pathogens from one plant to the next during a precipitation event.  Second, it increases air flow through the plant, which can reduce the likelihood of pathogen spores that might float in and land on foliage.  Third, it reduces humidity in the immediate microclimate around the plant. The increased air flow in addition to the reduced amount of foliage that is releasing water through transpiration can have a significant effect on the humidity, which can have a big effect on the germination, establishment, and survival.  
  • Utilize diverse planting plans in the vegetable garden and the landscape.  Research shows that while having a variety of plants increases the diversity of disease organisms, it actually reduces the infection rate possibly because pathogens splashing from plant to plant are less likely to find a host plant if they are surrounded by non-host plants.  This practice is promoted in intensive vegetable plantings such as square foot gardening. 
  • As stated earlier, precipitation can drastically increase the population of microbes on foliage.  This also includes water from overhead irrigation.  For example, this study found that overhead watering of cabbage led to significantly higher and faster rates of spread of the black rot fungus as compared to drip irrigation.  Therefore, reducing or avoiding overhead watering can reduce the likelihood of disease incidence. 
  • Timing of watering may also contribute to disease development.  The dew point, which usually happens during the night time hours, is when the air is totally saturated at 100% relative humidity and therefore cannot hold any more water.  This is the point where excess moisture is deposited as dew on surfaces (another source of water on the foliage) and little to no evaporation of water already on surfaces happens (learn more at weather.gov).  As shared in this book chapter review, lower temperatures resulting in reaching the dew point can extend the time leaves are exposed to high moisture and result in higher disease incidence. 
  • As our own GP Linda Chalker-Scott points out in this review, mulching not only retains soil moisture, reduces erosion and more but also reduces the incidence of disease in plants by reducing the splashing of soil or spores from rain or irrigation onto the plant.  This drastically reduces disease spread from pathogens found in the soil or on plant debris.  The organic matter from organic mulches also has the benefit of increasing the population of beneficial microbes, which out-compete the pathogenic microbes. 
Mulching and drip irrigation can both significantly reduce disease incidence in gardens.
  • Crop rotation, where crops are not grown in the same soil or plot for a number of years, also reduces disease incidence by reducing pathogen loads in the soil or from crop residues left in the garden.  This study shows significantly reduced disease incidence on potato and onion when a crop rotation plan of four years is utilized (meaning that either onions or potatoes are not planted in the plot for a minimum of four years, with other crops planted between those years). 
  • If root rots and pathogens are a problem, try improving drainage around the garden. Adding organic matter can help with water permeability of the soil over time. Raised beds can also drain faster than in-ground gardens.
  • Of course, if you’re having lots of problems with certain diseases on your plants, these cultural controls may not be enough.  Finding resistant varieties may be a necessary step in breaking the disease cycle in your garden.

Overview

While water is required for plant growth, it can cause issues with plant diseases if there is too much or if it lingers on the wrong parts of the plant for too long.  Water from rainfall, irrigation, high humidity, fog, and dew can all lead to the initiation, development, and longevity of plant fungal or bacterial diseases.  Reducing the amount, persistence of water or humidity on or around foliage can significantly reduce the likelihood of plant disease incidence.  Methods such as reducing overhead irrigation, timing of irrigation, mulching, and crop rotation are key cultural methods in reducing diseases spread by water. 

Sources:

Aung, K., Jiang, Y., & He, S. Y. (2018). The role of water in plant–microbe interactions. The Plant Journal, 93(4), 771-780.

Burdon, J., & Chilvers, G. A. (1982). Host density as a factor in plant disease ecology. Annual review of phytopathology, 20(1), 143-166.

Café-Filho, A. C., Lopes, C. A., & Rossato, M. (2019). Management of plant disease epidemics with irrigation practices. Irrigation in Agroecosystems, 123.

Chalker-Scott, L. (2007). Impact of mulches on landscape plants and the environment—a review. Journal of Environmental Horticulture25(4), 239-249.

Krauthausen, H. J., Laun, N., & Wohanka, W. (2011). Methods to reduce the spread of the black rot pathogen, Xanthomonas campestris pv. campestris, in brassica transplants. Journal of Plant Diseases and Protection, 118(1), 7-16.

Rottstock, T., Joshi, J., Kummer, V., & Fischer, M. (2014). Higher plant diversity promotes higher diversity of fungal pathogens, while it decreases pathogen infection per plant. Ecology95(7), 1907-1917.

Wright, P. J., Falloon, R. E., & Hedderley, D. (2017). A long-term vegetable crop rotation study to determine effects on soil microbial communities and soilborne diseases of potato and onion. New Zealand Journal of Crop and Horticultural Science, 45(1), 29-54.

Catch my Drift? Herbicide Drift, Curling Tomato Leaves, and Food Safety

There’s all kinds of maladies that can strike your garden plants throughout the season- diseases, insects, negligence, and more.  But one common issue we are seeing more and more here in the corn belt and other places with lots of crop production is herbicide drift.  Of course, you don’t have to have a corn or soy field nearby to have issues with drift – it can happen anywhere and anytime an herbicide is applied and proper precautions aren’t taken, even when you or a neighbor are just treating a small area in the yard.  There are other avenues of herbicide damage on plants as well, such as using herbicide-treated grass clippings as mulch in the garden.

 A wide variety of plants can be damaged by herbicide drift from a variety of different products – trees, shrubs, roses, vegetables, and more.  The damage can be slight to severe, and unless the dose is large most plants will grow out of the damage.  Vegetables and fruits, though, are of particular concern due to the potential food safety risk from residues of unknown herbicides on the plants.  Therefore, it is especially important to be able to identify signs of herbicide drift and take the appropriate course of action which is usually and unfortunately removal of the plant from the garden. 

I have to remove the plants!?!?

Yes, you read correctly, I said removal of the plant!  I, along with many of my extension colleagues, encourage gardeners who have drift or herbicide damage on their plants to remove them from their gardens. Why take such a drastic measure, especially if the plant may actually recover and “grow out” of the damage?  The answer is mainly one of safety.  Since it is likely impossible to know exactly which chemical or product formulation was used there’s no way of knowing if the product is safe to use on consumable crops, whether its residue is safe, or whether it is systemic and has a residual effect.  A gardener cannot know if there is a pre-harvest interval where the crop will be safe after a certain passage of time or if it will never be safe.  And even if you do know the product (let’s say you were the one that used it or you know what is being used by the neighbors) it is likely that there won’t be safety information for use on fruit and vegetable crops, since we don’t typically apply herbicides to plants we want to keep growing.  You should also remember that application of such herbicides to fruit and vegetable crops, even if accidental, technically constitutes an off-label (and illegal) application of an herbicide to a non-target crop or pest. 

What are the most likely fruit and vegetable plants to be damaged from herbicide drift?

While just about any plant can be damaged by herbicide drift if enough herbicide gets on the plant, there are a few plants that seem to be more susceptible to herbicide drift.  This means that these plants exhibit damage with smaller doses of herbicides than others and will show damage while other plants nearby remain unfazed.  The plant that we get the most calls about are tomatoes.  This is the vegetable garden crop that is the most susceptible to herbicide drift and just so happens to be the most widely planted crop in the garden.  The other edible crop that seems to be highly susceptible to herbicide drift is grape.  While grapes aren’t nearly as common as tomatoes in home gardens, wineries in regions with high herbicide use rates are struggling to keep their vineyards going due to the damage.

I live nowhere near a big farm, how do I keep getting drift damage?

Of course, drift can come from anywhere, even a small application of herbicide on a neighborhood lawn or garden.  But under the right weather conditions (high temps and wind) some herbicides like dicamba can volatilize and drift for 2-3 miles or more.  Even if you think you live nowhere near a farm or other area where herbicides might be used you can get drift from miles away.  This makes it hard to pinpoint where the damage is coming from in order to sleuth out what exactly was used.  This is especially tricky here in our area where the city of Omaha is surrounded on all sides by farmland, and even has pockets of productions fields sandwiched between residential areas.  Unfortunately, one of the prime herbicide application times in our region is shortly after most gardeners plant their tomatoes so we get lots of calls and questions that end up being drift.  Thankfully there’s usually still time to replant tomatoes, but it isn’t fun telling people that started plants of their favorite or special varieties that they’ll have to rip them out and go buy new plants. 

The kicker is that drift can be random.  It can be one or two plants out of a bed of twenty, or one plant on one side of the garden and another somewhere else, or an entire field full of plants.  It just really depends on the wind patterns and concentration of herbicide. 

Is it drift?  Or is it something else? 

At first glance it can be hard to tell if an issue is drift or something else since the signs can look like some other problem until you get up close.  There are a wide variety of herbicides on the market and therefore there can be lots of different signs.  The most common types of damage you’ll see are light/white colored and necrotic spots from exposure to broad-spectrum herbicides like glyphosate, and curling, twisting, stunting, yellowing, and epinasty from broadleaf herbicides like 2,4-D and dicamba.  Epinasty is an unusual, twisting growth pattern on the leaves that result when one layer of the leaf (usually the upper layer) grows faster than the other.  You can get weird strappy looking leaves, weird margins, and other irregular growth patterns.  The damage from broadleaf herbicides can sometimes be mistaken for heat or drought damage, viral diseases, or even excess watering, all of which cause leaf curling of some sort.  I’ll share a few tomato pictures below to demonstrate herbicide damage vs other types of leaf curling.  For a great pictorial guide to herbicide damage symptoms, check out this resource form the University of Tennessee

Symptoms of broadleaf herbicide (such as dicamba or 2,4-D) drift damage on tomato. Notice the irregular margins, strappy appearance, and curling of the leaves. The damage is usually limited to a small area on the plant. Photo: Patty Leslie

Note the irregular growth patterns of the leaves in this sample. Herbicide damaged leaves cannot be flattened out to look normal. Photo: John Porter
Widespread damage, likely from application of herbicide-treated grass clippings as mulch. Photo: John Porter
Leaf curling likely from excessive heat, NOT herbicide damage. Note that the leaves could be flattened to look normal. Photo: Scott Evans

Can you avoid drift?

Unfortunately, you can only control drift from the herbicides you apply yourself.  Pesticides such as herbicides can be used safely and effectively if used appropriately.  Reading and following the label instruction is important and is the law, paying special attention to wind speed, temperature, and application equipment, e.g., how fine of a mist does the nozzle create.  Drift from the neighbors’ lawn treatment or a nearby farm is really outside of your control, so being watchful for signs of drift is important.  Sheltering susceptible crops, like tomatoes, using something as a windbreak might be helpful.  As this journal article points out, a windbreak or vegetative buffer around wetlands offers some protection and I noticed a similar effect recently in one of our Master Gardener project gardens.  Our Master Gardeners grow thousands of pounds of produce a year for local food banks, and on a recent visit I noticed that about 25 percent of their tomato plants were showing signs of drift (and they were removed and replaced).  The pattern was interesting – the only plants damaged were the ones on the outside edge of the garden and the ones along wide walkways in the garden.  But plants in the interior were spared.  So perhaps planting less susceptible crops on the exterior of the garden and along walkways to act as buffers might work. 

And while it isn’t useful for home gardeners, specialty crop producers (like those all-important wineries) and beekeepers can register for a program called DriftWatch where they can be informed when spraying will take place on local farms. 

Contain Yourself: Vegetable gardening in containers and small spaces

Given the growing (haha) popularity of vegetable gardening over the last several years, which has gone into overdrive during the pandemic, more and more people are looking for innovative ways to grow in all kinds of spaces. Container vegetable gardening can be as simple as popping a tomato into a bucket, but there are lots of different ways to successfully grow crops in small, mobile containers. It is possible to grow full sized crops in containers, given a large enough container and space to grow. But more and more plant breeders have been developing small and dwarf cultivars of lots of different kinds of crop plants to meet the burgeoning interest in container and small space gardening. Let’s talk a bit about growing in containers, about some of those crops that do well in containers (including some dwarf/small cultivars, and even some design to make those vegetable containers attractive on your patio or porch.

Container Culture

Growing vegetables and fruits in containers follows the same general rules that ornamentals and houseplants follow. We’ve covered several container questions here on the GP blog, which you can find here. Probably one of the biggest questions (and myths) that we encounter is the placement of rocks or other items in the bottom of pots for drainage. It is a common question over on our social media. So to just get that out of the way, don’t do it – it actually makes drainage worse. The only exception might be if you are using a really large, deep pot and need to fill it with something so you don’t have to fill it all the way with soil – but you still need to ensure that the soil is sufficiently deep so that you don’t end up with waterlogged soil in the root zone.

Here are some other best practices to keep in mind:

  • Use only good quality potting mix, not garden soil, top soil, or “bargain” potting mix. Container culture means that soil needs to be “light and airy” to ensure proper balance of soil, air, and water.
Leafy greens can be grown in shallower pots than bigger crops like tomatoes and peppers.
  • Choose the right size and shape of container for the job. You have to look at container diameter for the plant size, but also ensure the proper depth and volume of soil to support root growth. Small crops like leafy greens can make do in a shallower container, but large rooted plants like tomatoes and peppers will require a larger volume. For example, you can grow one tomato plant in a five gallon container (if you’re a “thrifty” gardener, this means you can drill some holes in the bottom of a food-safe 5 gallon bucket). But you can also grow 12 carrots in the same size container, given that the soil is deep enough to accommodate the carrots. For a good size and spacing chart for “standard” sized crops, check out this table from UF Extension.
  • Drainage is a must. Make sure your containers have good drainage holes (and don’t add rocks!). If your containers are in an area exposed to rain, it would be best not to have saucers under them so that they don’t sit in water.
  • Make sure the containers are food safe. This isn’t an issue if your using just about any purchased container meant for container gardening, but if you’re repurposing containers you want to make sure they won’t breakdown or leach chemicals into the soil. Some plastics will break down in sunlight, but most should be food safe. The one big exception is plasticized (softened) PVC. Hard/rigid PVC is OK, but the softer plasticized versions can release dangerous phthalates when breaking down. You can look for the number 3 in the recycling symbol to know if you have PVC, and if it is soft and pliable don’t use it. Galvanized metal is another risk, as it can release zinc or cadmium into the soil both of which are harmful to humans. This is alarming as metal containers and raised-bed garden kits have been hitting the market and lots of people grow in galvanized livestock tanks. Be sure if you are using metal containers that they are either not galvanized or are sealed (or you create a barrier) if they are.
  • Make sure the light is right. Growing in containers doesn’t mean that tomatoes and cucumbers will become shade-loving plants. You’ll still need a minimum of 6 (preferably 8-10) hours of full sun for most fruit or root crops. You can grow shade tolerant crops, like most leafy greens, in shaded areas such as covered porches and under trees.
  • Nutrients are limited to what is in the potting soil, so keep an eye out for signs of nutrient deficiency and fertilize accordingly. Most potting soil comes with an initial dose of fertilizer, but you’ll probably need to add more through the season.
  • Keep on the lookout for insects and diseases – they still happen in container plants, too.

Little Plants for Big Flavor

It is possible to grow most standard vegetable plants in containers, save for maybe giant plants like pumpkins and some squashes. However, breeders have been developing numerous crops in small, container-ready sized plants over the last decade or so. These cultivars can let you grow more plants in smaller containers. For many, the fruit or harvestable portion is similar to that of the standard sized plant, but for others the edible parts are miniature themselves. These plants are not just cutesy wootsy (though they really are that), but they are also great alternatives to pump variety into any sized garden.

Pepper Pot-a-peno - AAS Edible - Vegetable Winner

As a trial judge for the All-America Selections program, I’ve had the pleasure of trialing several plants over the last few years that are great for containers, including the 2021 AAS regional winner Pot-a-peno jalapeno pepper bred by Pan-
American seeds. I’m excited that this year, a new trial has been added to the program to specifically trial plants for container growing, so be on the lookout for more container garden winners in the future.

Container-sized vegetables come in all shapes and sizes. Some of my favorites are ‘Patio Choice Yellow’ Tomato, which grows 18 inches tall and produces numerous yellow cherry tomatoes and the 2-ft tall ‘Patio Baby’ eggplant that produces 2-3″ eggplants (both plants are AAS winners). There’s the cucumber with only 3 foot long vines called ‘Patio Snacker’ and a 4 inch cabbage head named ‘Katarina’. You can find a fairly good list on this document I put together for my container vegetable gardening workshop:

Mini varieties of plants have even created some community-driven projects, like the Dwarf Tomato Project that uses a co-op type process where home gardeners are crossing plants in their own gardens to develop new dwarf cultivars of tomatoes.

Vegetable Garden, but make it Pretty

Pretty Kitty Teacup, colorful tubs and trellises, and more: In and Out | Container  gardening, Planter trellis, Garden containers
Gardens like this tomato, pepper, basil and flower combo are common on places like Pinterest

Many who grow container gardens like to make attractive gardens to decorate their porches, patios, and decks. Vegetable gardens can range from the utilitarian (like a tomato plant in a 5 gallon bucket) to the beautiful. There are lots of ways to mix plants to get a good container design if that’s what you’re after. Mixing color, shape, and form of plants can be done just as easily with vegetables as it can be with petunias and geraniums. You can add in flowers for extra pops of color as well. All one needs to do is search the internet (especially places like Pinterest) to find ideas for dressing up container gardens. I talk about container designs with vegetables in my recent talk (recording shared below) and the plant list I shared above.

To (direct) sow, or not to sow, that is the question: whether ’tis nobler in the garden to transplant

Most experienced gardeners will tell you what should be started indoors (or purchased) as transplants and what should be direct sown into the garden, but this can often be confusing for new gardeners.  Add to the confusion the fact that some plants have a gray area when it comes to what is best, sometimes it depends on the time of year, and sometimes it depends on where you are as to whether what is possible.  So if you forget to start your favorite tomato or begonia indoors in time to transplant, do you have options?  Let’s explore!

Why start transplants, anyway? 

This is a good question.  Why do we take the time and energy to start seeds indoors, or the added expense of buying vegetable or annual transplants?  There are a few good reasons:

  1. Germination temperatures. Many of the plants that we traditionally start as transplants require minimum soil temperatures of around 60F and have optimum germination between 70F and 80F.  Waiting for soils to reach these temperatures, especially in cooler climates, can really shorten the growing season.  Vegetable temperatures, via UNL Extension
  2. Extending the growing season.  Related to germination temperatures, starting transplants for warm season crops before soil temperatures warm up and before the weather is suitable for planting can have a plant ready to go once those weather conditions are ideal.  This can give you a head start of weeks or months over direct sowing. 
  3. Ideal growing conditions.  Seedlings for many vegetable and annual crops are quite tender and dainty when they first start out and any changes in temperature, water, or even sunlight can cause damage.  This is even more important as spring weather is becoming a bit more unpredictable as the climate changes, where temperatures can drop suddenly and the weather can go from rainy to dry (or snowy) at the drop of a hat (he writes as the temps drop to the 30s and 40s from the 70s the previous week and some parts of the state are receiving 6+ inches of snow in late April). 

What about direct seeding?

  1. Ease.  Many gardeners, especially newbies, find it a lot easier and less intimidating to just hop out to the garden and plop seeds in the soil versus staring seeds indoors.  Of course, buying transplants is equally as easy, but that does limit the variety you have available to plant.
  2. Cost effectiveness.  Only needing a pack of seeds (or saved seeds) is typically much cheaper than buying transplants or buying the equipment than starting seeds indoors.  This allows for much better cost effectiveness for gardeners. 
  3. Some things don’t transplant well.  Root crops, like radishes, carrots, and beets don’t transplant well because damaging that tiny little root in any way as you transplant can damage the actual harvestable portion of the crop and result in much lower produce quality (or even loss).  Additionally, some plants don’t like to have their roots disturbed, even when they’re tiny little transplants.  Cilantro and zinnias, for example, don’t do well with root disturbance so if you do want to transplant them you’ll need to start them in large enough containers so that you don’t have to repot them, and then plant them carefully as to not disturb the roots.

So sow, or not to sow?  How do I know?

This is a good question. Oftentimes we can take a look at the seed packet and know, but sometimes we don’t have that packet or maybe we want to fudge a little with what we read on the packet.  So what is possible, and what is “best practice”? 

A newly transplanted pepper, getting a start for the season

Using some of the information we discussed previously about soil temps and growing season, most of those warm season crops you plant that take a while to grow from seed, like tomatoes, peppers, and eggplants should be started as transplants, especially for folks in cooler climates (like most of the US).  Same for those summer annuals (if you absolutely MUST grow annuals, I know some people love them and some loathe them).  In warmer or topical areas, you may be able to direct sow these crops, but they may still do better as transplants. 

Some of the warm season crops, like beans, corn, cucumbers, squash, and pumpkins can be started indoors and transplanted, but it isn’t necessarily needed.  These crops typically grow much more quickly from seed and the seedlings are a bit hardier.  We also typically grow some of these plants in much larger quantities, making them take up more space for indoor starting and resulting in a bit more work to transplant versus sow.  Therefore, it is usually easier to direct sow these crops, but there could be situations (like overcoming weed pressure in the garden or if you have a really short growing season or low soil temps) where you might want to start them indoors. 

What about cool season plants?  Sometimes the answer to this one is – “it depends.”   Lots of the leafy greens, like lettuce and spinach, and those aforementioned root crops can be direct sown into the garden well before the last frost date.  If you have a soil thermometer, or a nearby weather station with soil temp probes, keeping an eye for when soil temps get into germination range can signal when to direct sow outdoors. The leafy greens can be started as transplants, but figure out the optimum soil temperature for gemination – for some, like spinach, it may be way cooler than your indoor temperatures can get (unless you keep your house around 45 degrees).  For the Cole crops like broccoli, cauliflower, and cabbage, transplants should be started for spring planting, since they still require warmer (75ish degrees) temperatures for germination.  However, if you’re sowing them for fall crops you can possibly direct sow them if other conditions, like water availability and low weed pressure, will support good growth in the garden. 

There are several resources, like this graphic from Virginia Cooperative Extension, that can help you out.  But keep in mind that certain situations may make other options possible.  For example, this graphic is for spring planting, so some of the items, like the Cole crops, may have options for direct sowing for fall cropping depending on where you’re located and your local climate. 

Chart showing how to start vegetables transplant vs direct sow: Transplant: Broccoli, Brussles sprouts, cabbage, Chinese cabbage, Cauliflower, Eggplant, Leeks, Lettuce, head; peppers; tomatoes. Direct sow: asparagus; beets; beans, bush; beans, pole; beans, lima; carrots; chard, swiss; collards, kale; cucumbers; kohlrabi; lettuce, baby salad; muskmelons; mustard; okra; onion, bulbing; radish; potatoes; southern pea (cowpeas); spinach; squash, summer; squash, winter; sweet corn; sweet potato; pumpkins; rutabaga; radish; turnips; watermelon. VCE and Master gardener logo at the bottom with link to publication (also included in post text)
This info is good for many areas for spring planting, but climate and planting time can change options for some gardeners
Source: Virginia Cooperative Extension Master Gardener Facebook

Holy Hydroponic Houseplants, Batman!: Can you grow houseplants without soil? Yes!

Just when you thought you got the hang of growing houseplants in potting soil (or if you’re a doting plant parent, a special homemade mix someone on the internet told you to use) comes a new trend – hydroponic houseplants!  Or, “semi-hydroponic” to use the more technical term that is used when describing the trend.  How do you grow houseplants semi-hydroponically?  Do they grow this way?  But first, maybe we should ask the question – why? 

Why grow semi-hydroponically? 

I think for most casual houseplant growers, this method is attractive because it is a challenge.  Something new to try after you’ve mastered growing houseplants the old-fashioned way. And quite possibly a pandemic project to provide a distraction after being cooped up in the house for months on end.   But are there benefits to growing houseplants this way?  Turns out, there are some.    

Many articles you find on the subject state that semi-hydroponic houseplant growth can be beneficial for those who struggle with chronic over- or under- watering.  The media used for semi-hydroponics is a big, porous puffed clay stone called hydroton or LECA (Lightweight Expanded Clay Aggregate, of course we have to have an acronym!).  It is used in some hydroponic vegetable (and other plant) production systems.  The large pore spaces it creates and the wicking action it does in the container helps keep a balance of air and water for the roots. The #1 leading cause of death among houseplants is overwatering – it creates a lack of air in the potting media, the roots lack oxygen (called hypoxia), and are either damaged or die.  This can also make it easier for fungal infections to cause root rots.  But how can you stop from overwatering plants if you’re growing them in water?  We’ll talk about that in a bit when we talk about the “how to”. 

There are some houseplants, like epiphytes, that might also benefit from having a media that isn’t like soil.  Plants that are used to growing on tree bark, or in rocky environments in their native habitat that might actually perform better in a media that is a large, rough pebble that does kind of resemble the texture or tree bark or stones.  There are lots of tropical houseplants that also grow in areas with high levels of large particulate organic matter like chunks of wood and bark.  Plants from boggy environments that have high water requirements or grow in a more “mossy” type soil might also benefit. 

One other application of this method is for propagation of cuttings.  Many houseplant growers like to propagate cuttings in water, but this often isn’t the best practice because the water can be depleted of oxygen (causing hypoxia and rot) or become spoiled or soured (and cause infections).  Most horticulturalists will recommend propagation in a light media like seed starting mix, perlite, or sand.  But keeping water consistent without overwatering is difficult in this situation, and media can also be a vector for disease.  The air space and wicking action of the LECA media used for semi-hydroponics can help keep cuttings hydrated without the issues of water propagation.  This method is commonly done in clear class containers, so there’s the added benefit of being able to see root growth to monitor progress. 

How do you grow semi-hydroponically?

Of course, in this short article we won’t be able to cover every detail, so if this is something you’re interested in trying, I’d suggest some self-study.  I’ll be covering some of the basics, but there’s a lot more to learn. 

The Kratky Method - Grow Food The Passive Hydroponic Way (Step by Step  Guide) | Trees.com
Kratky hydroponic method Photo: UpstartFarmers

First, this method somewhat resembles one of the simplest forms of hydroponic production that lots of home hydroponic gardeners use, called the Kratky method.  In this passive hydroponic method, a plant is suspended above a water-based nutrient solution.  At first planting, the nutrient solution is right below the plant, close enough for a few inches of the roots to touch the solution.  As the plant grows, the roots elongate and the nutrient solution level is reduced to keep just a few inches of the roots submerged.  This allows the roots to take up solution, but the space between the plant and the solution allows a majority of the roots to be surrounded by air to avoid the issues of hypoxia. 

In semi-hydroponic houseplant growing, a container (usually clear glass, at least for beginners) is filled with the LECA media and the plant’s roots are distributed through the media.  (The media should be washed and soaked in water first, to remove dust and allow it to hydrate.)  It is easier if it is a young plant or recent propagation so you don’t have too many roots to deal with (you may need to root prune larger plants).  Smaller plants will also withstand the shock of going to this system, especially if they’re moving from a potting soil media.  (Note: Clear glass container + nutrient solution + light = algae. Be prepared to clean up the algae from time to time.)

A (dilute) nutrient solution is added to the container.  The roots should not be submerged in the solution, but rather it should be added to a level where it will wick up through the media to surround the roots.  The basic rule of thumb is to fill the container about 1/3 of solution, but if the container is exceptionally large or the roots are very small, you may need to fill it higher to make sure the media around the roots stays hydrated. 

This nutrient solution is one of the trickier parts.  You can use a general all-purpose hydroponic nutrient mix, available in lots of garden centers now or online.  You can also try some of the general houseplant fertilizers or ones specific to whatever houseplant you’re trying to grow.  You’ll want one with micronutrients as well as the macronutrients like N-P-K – since we’re growing without soil or an organic matter based media you’re going to have to supply all of the plant’s nutritional needs.  You’ll want to mix the solution between ¼ – ½ the recommended strength – you’ll need to see what works for you and your plant.  And then you’ll want to pH balance the water to create the right environment for the plant and make sure that nutrients are available for uptake.  The pH range for most plants is between 6.0 and 7.0 (aim for 6.5), unless you have one with specific needs.  For this you’ll either need pH test strips or a meter (which you can now get for less than $20 online) and some acidic and basic solutions to adjust pH (you can use some household items like vinegar to do this, but your best bet would be solutions specifically prepared for adjusting hydroponic or aquarium pH levels commonly referred to as “pH up” and “pH down”).  This pH adjustment is a lot easier (and maybe unnecessary) if you start with distilled or reverse osmosis water (or if you have a really good water filter that removes dissolved solids).  The pH levels and dissolved solids in some tap water makes it hard to adjust (my water here in Nebraska is very basic because it is very heavy due to high calcium levels, which also throws off the nutrient balance). Rainwater or melted snow can also work (though may not be pH balanced). 

You want to keep the solution topped off so that the media stays sufficiently moist. As with hydroponic production, plants pull nutrients out of the solution at different rates, so you can get build-up of some nutrient salts over time that could result in poor growth and even toxicity.  To avoid this, every few weeks (or more often if your plant is a heavy drinker) you might need to perform a flush, where you drain off the nutrient solution, give a quick rinse with tap water, and start over with fresh nutrient solution. 

More experienced growers might graduate to using this method in containers other than clear glass.  This adds a level of challenge, since you can’t automatically assess the level of nutrient solution by visual inspection.  The use of self-watering pots that have net pot or hole-y insert pots are commonly used for this.  Or you can buy net pot or orchid pot plastic inserts to use in any non-porous container you desire.  Growing in net pots can make the flushing process easier, since you can just pop it out of the container and run tap water through it.  Otherwise, you’ll have to find a way to pour the tap water out of the container or

completely remove the plant and wash the media. 

What can I grow semi-hydroponically?

Well, you can try with a lot of different plants.  I don’t know that there’s a list of plants out there for do’s and don’ts, but there are a few good candidates to try. Most tropical houseplants are good candidates. I’ve seen lots of articles on orchids, and I just recently put a rescue phalaenopsis in semi-hydroponics.  Other epiphytes like holiday cacti and bromeliads are also good candidates – think of things that like to grow on trees/treebark. Hoya, which are all the rage in houseplant circles, are also candidates due to their mostly epiphytic habits.  Lots of tropicals like Monstera, Philodendron, and Pothos also do well in this system.

Things that probably won’t do the best in this system are ones that don’t like to have “wet feet” – I’m thinking mostly desert cacti and succulents. But some of the LECA lovers that I talked to said that some succulents, like “string of pearls” and other strings of things (hearts, dolphins, turtles, etc) do grow well. But if we take a look at their natural habitat, where they grow over rocky outcroppings, it makes sense.

There isn’t really an exhaustive list, so you might want to experiment if you’re wanting to try it out. As long as it isn’t an expensive plant (and there are lots of expensive houseplants out there), a little experimentation can help you find the plants that would work best for you and your situation. 

In conclusion…..

Growing houseplants semi-hydroponically isn’t for everyone.  Getting everything just right can have a learning curve, especially if you weren’t great in chemistry class.  But, it can be a fun way to challenge yourself and may also benefit your plants in the right situations.  It is becoming so common that the materials are getting easier to find – many garden centers now carry the LECA and hydroponic supplies, you can always order them online, and you can even find small bags of the LECA/hydroton in the ever expanding houseplant section at IKEA (of all places, if you’re lucky to have one).  So if you’re up for a challenge, give it a try!  You might find a fun new way to grow houseplants….or a new way to kill houseplants!  But the fun will be in the trying. 

Special thanks to:

  • Anni Moira
  • Sydney Tillotson Sehi
  • Suzi Sellner
  • Tiffany Caldwell
  • Shelbi Sorrell
  • Maggie Pope

Sources:

Houseplant Hubub: The rage about variegation

It is no secret that houseplants are hot right now.  Interest was growing before the pandemic, especially with millennials and younger folks.  Then the pandemic hit.  Houseplant interest skyrocketed since people were stuck at home and wanted to bring a little bit of nature indoors to make their spaces a little more cozy for 24/7 habitation. 

This has caused the demand, and price, of many houseplants to increase, especially if they are on the rarer side.  One thing that increases the price of many plants is when a variegated version of a standard plant has been developed. 

My reading nook/houseplant oasis

Just as an example, after posting a photo of my “reading nook/houseplant oasis” in my home office I was informed that variegated form of a Monstera deliciosa vine that I had was the highly sought M. deliciosa “Albo-Variegata” cultivar, usually referred to as a Monstera albo, or just Albo.  Folks were reaching out to buy cuttings right and left.  I ended up selling 5 single leaf/node cuttings over one weekend and made $675 in the process.  That’s right, $675!  The most variegated of the leaves sold for $200, and that was actually a bargain price.  The garden writer for the local paper, the Omaha World Herald, even picked up the story and shared it as a focus on the four new houseplant shops that have popped up in the city over the last few months.

Had my plant not had the variegation that made it an albo, each of those cutting would have been worth a few dollars apiece.  So what makes some plants variegated and others not?  Sometimes the variegation is the standard form found “in nature” and sometimes it is a cultivar or variety that has been bred or discovered by chance.  Let’s take a look at all the ways that a plant can get that variegation, whether it is standard or rare. 

Chimeric variegation

My Monstera albo that caused the hubub

This is a common form of variegation and the one responsible for the variegation of my Monstera.  In this form, a genetic mutation in some cells changes that cell’s ability to produce chlorophyll.  It may reduce chlorophyll production, resulting in yellowish or silver coloration, or eliminate chlorophyll altogether, resulting in white coloration. 

The name chimeric or chimeral is based on the fact that the plant displays two (or more) chromosomal patterns on one plant.  In Greek mythology, a Chimera is a frightening fire-breathing female monster with the head of a lion, body of a goat, and the tail of a serpent. 

Image result for chimera
An ancient chimera statue

This variegation can be stable, where the pattern persists throughout the plant.  Or it may be unstable, where it is random on certain leaves and parts of the plant can revert back to the standard green form.  These plants can also produce leaves that are almost totally white, which usually results in a leaf that will die since it can’t photosynthesize. 

This type of variegation also means that cutting or propagations may or may not be “true” to the pattern.  It can be random.  For my Monstera, the presence of white striping in or around the node that will become the new plant is the important marker for whether the new plant will be variegated or not. 

One common chimeric houseplant is the plant formerly known as Sanseveria, now a Dracena (Snake plant or mother-in-law’s tongue). Many of the different color patterns on some of the cultivars are due to cuttings taken from different parts of the “original” natural type that display different colors on them.

Viral Variegation

Image result for tulip mania
Viral variegation that was all the rage in Tulip Mania

While beautiful, this variegation will often reduce the productivity of plants if not kill them outright.  There aren’t a lot of houseplants that have this variegation, but some Hosta cultivars do.  Probably the most famous case of viral variegation is the Tulip Mania during the Dutch Golden Age (in the 1600s).  Prices of tulips skyrocketed and people were buying them as investments (maybe like the current houseplant craze, or GameStop stocks, or bitcoins).  Unfortunately, as the virus reproduced plants kept getting weaker and weaker.  Eventually the tulip market collapsed and lots of people went broke.  Let’s hope that doesn’t happen with the houseplant market….at least with my fancy Monstera. 

Natural Variegation

Natural variegation on Tradescantia

This type of variation occurs when the patterns or colors of the variegation are written into the DNA of the whole plant.  It will occur regularly throughout the entire plant, not randomly on some parts as in chimeric or viral variegation.  This variegation is passed through cuttings and usually through sexual reproduction from seeds as well, though different variations may pop up that cause a more desirable or rare cultivar. 

Common houseplants such as Tradescantia, Maranta (prayer plant), and many more common plants have this type of variegation. 

Blister, bubble, or Reflective Variegation

Reflective variegation on Phildodendron ‘Birkin’ following veins in the leaf

This type of variegation occurs when there is an air pocket or bubble between the lower layer of tissue and epidermis, or skin, of the leaf.  The lower level typically has green pigmentation from chlorophyll and the epidermis does not, resulting in a pattern that is usually white, silver, or yellowish though other colors could appear.  This pattern can be blotchy or splotchy like in some types of Pothos and Pepperomia.  It can also occur along the veins of some plants, resulting in white or silver veins on green leaves, as in some Alocacia, Anthurium, and Philodendron varieties. 

In conclusion…..

Even if you don’t have an expensive plant hiding in the corner, houseplants can add lots of fun and color to your living spaces.  And sometimes, your houseplant obsession can even pay for itself.  Online swap and sale groups have houseplant afficionados swapping and selling cuttings and plants all over the place.  So enjoy your plants….and maybe you’ll find a cash cow hiding in the corner.  Don’t mind me….I’m just over here propagating more Albos to fill up my “mad money” jar. 

Sources

Variegation mutants and mechanisms of chloroplast biogenesis

Variegated Indoor Plants: The Science Behind The Latest Houseplant Trend

Chimeras and Variegation: Patterns of Deceit

Tiny plants that pack a flavor and nutrition punch: getting in on the microgreen trend

If you do any searching for gardening (or even think about the color green), you’re likely bombarded with adds on social media and search engines about all stuff gardening.  One of the recent trends is microgreen production.  There’s all kinds of fancy little systems and gizmos that will help you grow microgreens for a price.  But what are microgreens?  Are they the same thing as sprouts? And do they have the same food safety issues as sprouts?  Let’s discuss, shall we?

What are microgreens?

Microgreens are basically tiny plants harvested shortly after germination.  Unlike sprouts, like the common alfalfa or bean variety, these baby plants are grown on a medium of some sort and just the “above ground” portion of the plant is harvested.  Sprouts, on the other hand, are typically grown in a moist environment without a medium and harvested whole -roots, seed, and all.  It is this wet and warm environment that make sprouts especially risky for food borne illness. 

Microgreens can be any number of different crops, but common types are kale, mustard, chard, broccoli, arugula, and radish.  Sunflower and pea are also common, but they fall more in the “shoot” classification since they are harvested a bit larger.  There’s lots of other crops that are used for microgreens, including herbs like cilantro and even marigolds, so the sky is the limit!

Why microgreens?

There are a few things that make them attractive to farmers which also are good for home growers.  First, it only takes 1-3 weeks for a finished crop.  This fast turn-around makes it easy to keep up with production needs for customers (or your own uses) and also reduces risk.  If a crop fails, it is much less damaging if it only took a week to grow rather than a whole field full of peppers that have been growing for months getting wiped out by disease or a storm. 

Second, is the value and profit.  While there is some investment in seed starting equipment and then continued expenses of seeds, trays, and media, microgreens have a high per pound value.  Microgreens are used in small quantities and are therefore sold in small quantities.  A small amount you may purchase at a farmers market for a few bucks may be an ounce or less.  When you calculate it out by the pound, microgreens are sold for between $20 and $200ish per pound (depending on the variety, organic production, other factors). 

And of course, microgreens lend themselves to year-round production.  It can be a fun and easy way to get some flavor and color on the plate even in the dead of winter.  Just a few square feet of production area can provide a decent sized crop, so it is great for those with limited space or no garden at all.

Look ma….I made fancy mac and cheese. All I had to do was add some microgreens.

Microgreens are popular with home cooks and chefs alike because they pack a flavor punch and add some color and texture with just a pinch or two of product.  Studies have shown that microgreens also pack a nutritional punch in a small package.  However, production practices can greatly influence nutrient content, especially light.  Microgreens grown with higher quantities (brightness) and quality (spectrum colors, mainly red and blue but also green) of light have higher nutrient values. 

How do you grow microgreens?

The way you grow microgreens lends itself to why they are so popular to grow, for both home enthusiasts and farmers alike.  Microgreens are basically recently germinated seedlings.  If you are good at seed starting, you can be good at growing microgreens.  Lots of the ads I’ve been seeing recently are for attractive but pricey growing trays and mats that you just lay down and water.  However, budget conscious gardeners can grow them pretty simply and inexpensively at home.  And you probably have most of the equipment you need, especially if you start your own seeds each year! 

Microgreens are usually grown in those flat plastic seedling trays, the type that don’t have cells in them (the ones used to hold the cell packs).  For those “in the know,” they’re called 1020 trays.  You can either use a sterile media like peat or coir or purchase specific fiber mats (I have some made from hemp -they work well but smell like a moldy gym sock full of weed when in use). We’ll talk about the importance of a sterile media when we talk food safety. 

A demonstration of sowing microgreen seeds on hemp fiber mats.

The sowing density of seeds can vary by crop due to seed and seedling size.  Typically, one ounce of seeds can sow anywhere from one to eight 1020 trays.  In general terms, large seeded crops like chard and beets may take up to ½ cup per tray and small seeded crops like radish or kale might require ¼ cup.  Tiny seeded crops, like sorrel may need just a few tablespoons.  If you’re really into production, Penn State extension has an excellent Excel calculator to calculate seeding rates. Typically, you’ll broadcast the seeds on top of your media and then maybe sprinkle a little more media on top to make it easy (no dibbler here!).

Most seeds require darkness to germinate, as well as high humidity.  You can use humidity domes and cover trays with an opaque material to achieve this, or you can use the trick that producers use and stack trays on top of each other for a day or two.  This keeps the seeds covered and dark and preserves moisture and humidity.  Just unstack them after a day or two and stick them in their growing location.  As with seed starting, you’ll have the most success if you provide some good quality light and heat.  (You can search through old articles to find lots of info on seeds starting).  There’s research that shows that light is a big factor in microgreen growth, coloration, and nutrition levels. 

You’ll harvest your microgreens typically one two three weeks after sowing.  Typically, this is done after at least one set of true leaves have formed, but you can usually let them go until there are at least two (or sometimes three) sets of leaves.  To harvest, use a sharp, cleaned pair of scissors to snip the seedling off just about soil level, being sure not to disturb the media so that you don’t get it on your precious produce.

There should be no need to wash the microgreens right after harvest and before storage, since they’re typically grown in a clean environment.  Washing before storage can increase storage moisture to levels that support microbial growth, reducing storage time and also increasing the risk of human pathogens.  Instead, store microgreens (and most leafy greens) without washing and wash just before use. 

Working with a local farmer to demonstrate microgreen production at a regional production conference.

Food Safety

As we learned when discussing what microgreens are and comparing them to sprouts, we learned that microgreens have been found to have much lower risk of human pathogens.  However, the risk is not zero, especially if production practices are conducive to pathogens.  We just discussed that washing prior to storage can lead to microorganism contamination, but there are a few other areas where contamination is easy.  To reduce contamination, follow these steps:

  • Always use clean and sanitized trays or containers.  If reusing trays, be sure to wash with soapy water then sanitize with a dilute bleach solution or other approved sanitizer. 
  • Keep the production area clean and sanitized.  Microgreens are often produced on multi-leveled vertical racks, so contaminants can drip down.  Make sure all surrounding surfaces are clean.
  • Use sterile media for production.  This is typically a soil-less media made primarily of peat or coir, like a seed starting mix, or specialized fiber growing mats.  Do not use regular potting soil, any mix containing compost, or anything containing soil to avoid the introduction of human pathogens or other microorganisms that might affect the crop, such as those that cause damping off.
  • Use cleaned and sterilized seed. Many companies sell seeds specifically for microgreens that have been processed to remove pathogens.  I’ve seen seed production, and while it isn’t filthy, it typically isn’t sterilized to the level of food production standards.  You can sterilize common seed at home using a solution of hydrogen peroxide or vinegar.  For guidance, visit this guide from K-State extension.
  • Use a clean source of potable drinking water.  If you wouldn’t drink it as is, don’t use it.  Typically this means it should be straight from the tap of a trusted source. 

Conclusion

Growing microgreens can be a fairly easy and enjoyable way to produce something fresh and green year round.  In terms of production practices, it is basically ramped up seed starting where your seedlings only grow a few weeks before harvest. This makes it a fairly easy process and one that can be done almost anywhere.  If you’re looking for an indoor gardening project or just want to add a quick source of nutrients to your diet, give microgreen production a try. 

Sources and resources:

Microgreen nutrition, food safety, and shelf life: A review

Microgreens and Produce Safety

Microgreens—A review of food safety considerations along the farm to fork continuum

A step-by-step guide for growing microgreens at home