Planting Prognostication: Understanding last frost and planting dates

Except for areas of the US that are more tropical like southern Florida or Hawai’i, most gardener’s planting schedules are set around winter weather and the possibility of frost or freeze.  And even for gardeners in those more tropical areas, planting sometimes needs to be planned to schedule around the extreme heat of summer.  Understanding these planting times can really lead to success or failure, especially for vegetable gardens, tender annuals, tropicals, and non-dormant perennials.  There are a few tools that help us understand weather patterns and predict critical temperatures for planting, namely the USDA Hardiness Zone map and the Average Last Frost/Freeze dates.  The USDA Hardiness Map shares data on what the average coldest temperature is, which is key for selecting perennial plants that you want to survive the winter.  However, to know when to plant we look at the average freeze and frost dates.  There seems to be a little bit of mystery, and even confusion, around the dates and how to interpret them, so let’s take a little time to understand them a little better.  And since my background is in vegetable production, I’ll share a bit more detail there in terms of plants – but you can translate the information to ornamentals, especially those that are frost tender pretty easily. 

Understanding Average Last Frost Date

What is the average last frost date and how is it figured?  The average last frost date is exactly what it says it is – the average date at which the probability of frost has diminished.  Just how diminished really depends on the source, so we’ll follow up with that in a bit.  The data is computed by NOAA (National Oceanographic and Atmospheric Administration) and the National Weather Service to determine the probability of temperatures relating to frost and freezes based on weather data for an area over the last 30 years.  They compute the likelihood of a light frost (36 F), frost/heavy frost (32 F), or freeze (28 F) at three different probability levels – 90% (the temperature is very likely to happen), 50% (the possibility is 50/50), or 10% (the temperature is unlikely).  This tool from NOAA provides a chart with probabilities for locations throughout each state.  

This data is typically collected and analyzed every ten years or so.  I’m not exactly sure when the last data was analyzed, but I did find some maps on the NWS referencing the period 1980/81- 2009/20 (below).  Therefore it is likely that new data will be released either this year or next year.

Temperature hardiness of common vegetables

Awareness of tolerance is especially important for vegetable crops, as the growing season and expected productivity of the plants.  The following chart is a general guideline, and your mileage may vary based on cultivar difference, microclimates, and other factors.  Also note that these temperatures are for both planting in spring and fall kill temperatures.  Some of the more tender plants, like tomatoes, may withstand colder temperatures when they’re mature so they may be less susceptible to frost at the end of the season vs. the beginning of the season. 

Season extension techniques, such as row covers can be used to protect tender plants in the spring and extend harvests in the fall.  Row covers can be selected by the degrees of protection they deliver.  For example, a row cover may offer 4 degrees of protection.  This allows the protected plant to withstand air temperatures 4 degrees colder that what it would unaided. For fall crops, note that plants may stop growing well before the kill temperature but will hang out in “stasis” until they are killed. The above NOAA chart provides probabilities for both spring and fall – allowing you to not only plan for spring planting but also for fall crops.  For scheduling fall crop planting dates, find your first frost date, count backwards the days to maturity (from the seed packet or tag), and add a few weeks for a harvest window and for the slowing growth as temperatures drop.

The Problem with Probability

These probabilities are based on past weather data, so keep in mind that these dates are used as a prediction not as a guarantee.  It is especially important to remember this as weather uncertainty increases with climate change.  Last frost could occur well before or even well after these predictive dates.  This also begs the question – which probability should you use?  Looking around at different sources, you might find sources that use either the 50% or 10% probability statistic, and there seems to be a bit of disagreement as to which one should be used.  Based on the data for my region, I’ve seen sources share both dates.  It really comes down to how much of a gamble you want to take or how much you want to push up harvest or maturity.  If you plant on the earlier 50% probability date you may end up having to cover the plants a few times to protect them from frost.  But each day that passes means that the chance of frost or freeze decreases.

Whenever I give a talk here at home in Omaha, I often ask my audience to guess what the average last frost date is for planting.  Invariably, the answer I get is Mother’s Day…which I guess works as a guidepost in general.  However, looking at the data (below), we can see that the 10% probability date for a 32 degree (killing) frost is May 4.  The light frost date is May 11 – plants may be damaged but not killed unless they’re very tender.  And the 50% probability date for a killing frost is actually April 21, which is the point where the probability of frost is 50% each day (and the probability shrinks each day.

Sometimes produce growers may opt to go early to get vegetables to market – which extends the sales season and allows them to charge a premium price if no other growers are selling.  Season extension techniques like high tunnels have also pushed back farm production dates.  As climate change makes weather more unpredictable, we may all be finding ways to alter the growing season as a norm rather than an exception.  Until then, we’ll rely on the data we have to make the best predictions.   

Sources:

https://www.canr.msu.edu/news/freeze_damage_in_fall_vegetables_identifying_and_preventing

http://www.gardening.cornell.edu/homegardening/scene0391.html

https://www.weather.gov/iwx/fallfrostinfo

https://www.ncdc.noaa.gov/cgi-bin/climatenormals/climatenormals.pl?directive=prod_select2&prodtype=CLIM2001&subrnum%2520to%2520Freeze/Frost%2520Data%2520from%2520the%2520U.S.%2520Climate%2520Normals

When Good Seeds Go Bad: How long can you store seeds?

Many gardeners, myself included, have that stash of old seed packets or saved seeds from garden seasons past, just waiting for the right time to be planted. They may be shoved in a drawer, a box, or in the fridge/freezer. Maybe you’re pulling some out of storage to start this spring – will they even germinate? Are those seeds good indefinitely? Do they ever expire? The answer to that really depends on what plant it is and how they are stored. While there isn’t a date where all the seeds go bad, they will eventually go bad over time. Why is this? And how can I make sure to use my seeds before they’re gone? Let’s find out!


Why Good Seeds Go Bad
While we think of seeds as perhaps inert, dormant, or in stasis they’re still very much alive and therefore are still undergoing processes like respiration, though at a much lower rate than a growing plant. During respiration, the seed (and plant within) are converting the stored sugars and starches in the endosperm to release energy. Once the germination process starts with the imbibition of water, the respiration rate increases drastically. A large amount of stored energy is needed to get through germination and sustain the seedling until it has its first set of true leaves and can photosynthesize on its own.

Seeds need to retain enough stored energy to sustain seedlings until they develop their first leaves and start photosynthesizing.

The shelf life of seeds is determined by the amount of energy that is stored, the amount used during storage, and the amount needed from germination to leaf development. This means that there’s a limit to how long a seed can stay in storage. After a while the seed loses viability if it doesn’t have enough energy stores to get it far enough along to photosynthesize on its own or to have that first burst of respiration at the initiation of germination. When searching for resources, keep in mind that viability refers to the ability of the seed to produce a robust seedling while germination refers to breaking of dormancy. The terms are inter-related, but the rates are not necessarily the same.

Some seeds have evolved to sit dormant for a long time, while others have a very short lifespan. It usually turns out that the seeds that last longest in storage are weeds that have evolved to wait long periods of time for an opportunity to germinate. Garden seeds tend to be on the shorter end of the storage time scale. A now 140-year old ongoing experiment at Michigan State University has given some interesting insight. In 1880, William Beal (one of the fathers of horticulture) buried 20 vials full of a variety of seeds (garden and weed) in secret locations around campus. The plan was to dig one up every 5 years and see what germinated. However, after the fist few rounds the cycle was bumped to 20 years. A vial was opened in 2000 and only one species, a weed, still germinated. This year is another germination year – we’ll have to wait and see if the mullein will germinate again this year.

How long will my seeds last?

Data from Nebraska Extension publication.

There are a few good sources that pull data from a variety of sources. The figure below lists some life expectancy times for common vegetable crops published by Nebraska Extension, using two common manuals on seeds as sources. You’ll also find some likes to other data, including average storage times for flowers, herbs, etc. in the references section (while we don’t typically promote commercial sites, the guide from Johnny’s Select Seeds has a good list of plants and has a variety of extension and academic sources listed). Like the MSU experiment, most of this research was done a while ago, but the data is still a good generalization. Most sources say that these time estimates are based on storage in optimal conditions. According to Johnny’s Select Seeds, “The actual storage life will depend upon the viability and moisture content of the seed when initially placed in storage, the specific variety, and the conditions of the storage environment”.

What are these “optimal” conditions? Generally the conditions are low humidity and low temperature. Low humidity ensures that the seed stays dry, avoiding potential initiation of germination. Low temperature reduces the respiration rate, slowing down usage of stored energy and increasing longevity. Optimal temperature for storage is below 42°F (15°C). Relative humidity should be between 20 and 40%.

The relationship between temperature and humidity seems to be inverse – meaning that as storage temperature goes lower, humidity can be higher and vice versa. However, storage times increase as both go down. Many sources state that seed longevity doubles for every one percent drop in humidity or five degree (F) drop in temperature. The relative humidity of the air affects the moisture level in the seeds. Germination usually starts at 25% moisture (and above). Ideal moisture levels for storage range between 8 and 12 percent and levels between 12 and 25 can lead to degradation of seeds, growth of fungi, etc. On the flip side, moisture levels below 5% can decrease vigor. Organizations like seed banks and germplasm centers that store seeds long term often will desiccate seeds to around 8% humidity to extend storage, but this isn’t usually needed for home gardeners.

Image result for seed vault
You don’t have to replicate conditions at the Global Seed Vault to have seed saving and starting success

Storage tips
Knowing that we need low temperatures and low relative humidity to extend seed life gives us some clues on how to store seeds to get the longest shelf life. This is key info if we’re trying to start seeds in spring that have been stored, or if we need to store extra or saved seeds. For the needed temperature levels, your standard home refrigerator is acceptable. Storage temps for cold foods are around the 40°F mark. However, humidity in a refrigerator is very variable. Humidity can skyrocket when doors are open, as condensation settles from warm room air settling on surfaces accumulates. Auto defrost cycles can also alter humidity. You’ll want to think about a desiccant like those silica packs to ensure that your seeds don’t get too moist. Store them in a plastic bag with the desiccant, and for added protection I always put mine in a sturdy container like a plastic box (or even a canning jar). Storing seeds in a freezer may help with the humidity issue, as any moisture that enters is frozen. You might also want to think about letting your bag or container warm up to room temperature before opening so that you don’t get condensation on the packets or the seeds themselves.

Sources:

Vegetable Garden Seed Storage and Germination Requirements – Nebraska Extension

Principles and Practices of Seed Storage – USDA

Seed Storage Guide – Johnny’s Select Seeds

Smith, R. D. (1992) Seed storage, temperature, and relative humidity. Seed Science Research 2, 113-116

120 Year Old Experiment Sprouts New Gardening Knowledge – MSU

Fail to Plan or Plan to Fail? Planning for a year of garden success

It seems like we’re always adhering to one schedule or another these days.  We have devices and planners to keep track of our appointments, our work schedules, kids schedules, and more. Heck, even the antique seed company clock in my office is telling me to order seeds.  It can seem overwhelming, so you might laugh if I tell you that coming up with a schedule, or a plan, for your garden can be beneficial.  It is especially helpful for vegetable gardeners or those who like to any kinds of seeds. 

Developing a yearly plan for the garden can help you keep ahead of the big tasks, help you stay on top of issues like weather, as well as make sure you get seeds started on time and transplanting done when it makes the most sense.  While some of this may be a review for seasoned gardeners, the number of questions and calls we receive at Extension (and the number of oopsies we see) means that the information could be helpful for many. 

Since my background is in vegetable production, I’ll focus there with some bits and pieces added for ornamentals when they fit. 

Do you have garden goals?

Whenever you are planning your annual vegetable garden, or planning on adding any ornamentals to your gardens or landscape, you should ask yourself a few simple questions.  When you’re dreaming of your garden during the winter is a good time to think of these goals.

1. What are my goals for the garden?  Do I have long-term goals?  What short-term goals can you set for this year to build momentum toward your long-term goals?

2. What resources am I willing to invest in the plants I’m ordering (money, time, water, space)?

3. What are the things I most want to grow?

4. What has worked (and what hasn’t) in your garden in the past?

While it may sound funny to say that you are going to set goals for your garden, it really isn’t all that far-fetched.

If you are planning to add ornamental plants to your landscape, you should think about what you want from those plants — are you looking for color or for structure? how about perennials vs. annuals (or biennials)?

When you are planning a vegetable garden, you should ask yourself not only what you want to grow, but how much. Are you just planting for fresh-from-the-garden eating, or do you want to preserve some through canning, freezing or drying? Are you growing just enough potatoes to eat for a month or two after the garden season, or do you need to select a variety that keeps well so you can store it?

Tips for Planning a Successful Garden

After you set your goals and decide what you want to plant, developing a schedule of when to do what is a good idea to stay on top of everything.  I can’t tell you how many years I had been planning on planting this or that, but then forget to buy what I need or start seeds on time.  A plan can help with that, as well as helping you space activities out over time rather than trying to get everything done in a hectic sprint.  This is especially helpful to new gardeners or busy folks who may forget to start or plant certain things at the right time (I wouldn’t be speaking from experience here.  Nope, this gardener has never been guilty of that.  I meant not to plant all of that garlic that I bought last fall.) To borrow the method used in a popular self-help book, you’re “scheduling the big rocks” as one of the habits of highly effective gardeners.

Keep in mind that it can be hard to “garden on a schedule” as weather always plays a factor in what we can and can’t do in the garden.  Given the wide variability in weather over the last few years in many parts of the country, which many scientists attribute to changing weather patterns due to climate change, it can be even more difficult to pin garden tasks to specific dates.  A plan can help you keep track of everything you need to do, but it should be flexible to take weather into account.

Starting Seeds Indoors

Germinating a variety of plants for our 2018 All-America Selections trials

If you’re starting seeds indoors, decide when you’re going to transplant them to the garden.  You can usually find this information on a seed packet, but you can find resources or consult your local cooperative extension office for guidance.  Keep in mind that warm-season plants typically need to be planted after your average last frost date (unless you’re adventurous and don’t mind gambling with a potential loss).  Cool season crops such as Cole crops (broccoli, cauliflower, cabbage, kale, etc.), leafy greens, and bok choi can be planted before the last frost date, but usually after the risk of a hard freeze has diminished.  For a map of the average date for last spring freeze/frost, check out https://www.ncdc.noaa.gov/news/when-expect-your-last-spring-freeze.  Note that these ranges are determined by analyzing the last frost dates over a 30 year period and the actual dates can vary due to weather variations (made even less predictable by climate change).

Choose the timeframe you wish to plant in the garden and count backward to when you need to start plants indoors. Put both the planting dates and the seed starting times on your calendar.   Also keep in mind that this is the earliest that you can plant warm season crops, but you can plant them later if it works better for you.  While we don’t typically share commercial links on this site, the best resource I’ve found for planning your seed starting and transplant dates for both vegetable and common annuals is https://www.johnnyseeds.com/growers-library/seed-planting-schedule-calculator.html

Direct Sowing into the Garden

For some crops like root crops, beans, leafy greens, and even some squash and cucumbers, direct sowing sees into the garden is ideal.  You can add timeframes to your plan based on previous practice, like knowing that you’ll sow carrots toward the end of March or early April, but keeping an eye on the weather can be even more helpful here.  Success here is more about temperature than timing.  Most plants have optimal germination temperatures, so you want to sow outside when the soil temperature (not air temperature) is at or near those levels.  The following resource has germination temperatures for common crops: http://sacmg.ucanr.edu/files/164220.pdf

If you’re lucky, you can search for local web-connected weather stations that have soil temperature probes.  For example, we have one at our office that we share with clients to make gardening decisions (http://mgextensionwx.com/).  If you can’t find one, NOAA has a few in each state for official climate data.  https://www.ncdc.noaa.gov/crn/current-observations.  Putting “check soil temperature” should be on your garden to-do list regularly until the temps get into good gardening range.

Spreading the planting and harvest through the season

If you’re aiming for harvests throughout the growing season, practice relay planting where crops mature in shifts throughout the garden season rather than all at once. If you’re planning on preserving some of your harvest for winter, planning on larger harvests at certain times in the season can get you the amount of produce you need for a big batch at the time that you need it. Some plants are good at producing through the season, but others, like determinate tomatoes and many beans have a one-time flush of production.  Of course, we also have the crops that are once and done, like carrots and radishes, that only have one harvest.  If we space out planting over weeks rather than planting all at once, harvests (or flowers if you’re growing annuals) can be spread out over a longer period of the season rather than everything maturing at once.  There’s generally a several week (to several month) window for planting crops.

For example, tomatoes can be planted as early as the average last frost date, but can be planted for several weeks afterward.  To figure out how late you can plant a crop, look for the first frost date and count backwards using the “days to maturity” information for the crop.  You’ll want to add on a few weeks to a month to account for having a harvest window and slowing growth as temperatures drop.  Keep in mind that many of the cool season crops can last well into the fall and winter, withstanding frosts and even light freezes, so replanting them for a fall harvest is ideal.

Planning out when to plant annuals, perennials, trees, and shrubs can also help make sure you get those plantings off on the right foot and can allow you to prepare in advance.  For example, if I want to add a tree to the landscape, taking the time to research trees and planting techniques, scheduling any prep of the planting area, sourcing the tree, and planting at the right time could all go on your calendar – that way you are prepared and ready to plant at the correct time.

Other garden tasks

While much of the work of a garden plan is front-loaded to the spring, there’s lots of tasks that we should be planning on doing regularly.  Scouting for and controlling insects and diseases, removing spent plants, mulching, compost turning, and more all come to mind.  Putting these on your schedule rather than  doing them when you think of them can really improve your likelihood of getting them done.  Also think about some of those big things you might have identified in the goals you set for the year.  Do you want to build a compost bin or develop new garden beds?  Plant some trees?  Take a soil test?  Putting these on your calendar can not only help you remember them, but plan ahead as well.  What do you need to do before you build that compost bin?  Do you need to buy supplies and tools (and look for bargains if you’re planning ahead)?  By planning when you’re going to accomplish these tasks, you can plan for success throughout the gardening year, improve your successes, and feel a little less hectic when the planting and growing goes full swing. 

A Cactus by Any Other Name: A Case of Mistaken Holiday Cactus Identity

Believe it or not, a cactus, of all things, is one of those plants that have come to represent the holidays and feature in the regular rotation of holiday houseplants. Then again, maybe it isn’t so strange amongst its peers that feature a flashy bulb-grown plant named for a horse’s head (the Latin name of amaryllis is Hippeastrum, literally meaning horse flower), a plant that has ugly flowers but brightly colored leaf bracts and leaks sticky and irritating latex when damaged, or some daffodil-like flowers that have musky odor so strong it makes some people nauseous.  But…..I digress. 

Back to the cactus.  However you see it though, the cacti that make their debut at the holidays are suffering under a case of mistaken identity.  What you typically buy as a Christmas cactus is not a Christmas cactus at all. It is actually a Thanksgiving cactus.  Now this wouldn’t be such a big deal, except that there is such a thing as a “Christmas cactus” — but you won’t find one on store shelves. Nay, it is hard to even find one in garden catalogs.  And this is sad, because the Christmas cactus is, I think, even more beautiful than the Thanksgiving cactus. 

How did we end up ignoring the beautiful Christmas cactus in favor of its holiday cousin?  It all comes down to timing and how we buy things for the holidays.  It seems that, as the shopping and holiday seasons creep ever upward on the calendar, retailers have little love for a cactus that is actually programmed to bloom at Christmas. They need something that blooms earlier so that it can be on the store shelves as early as possible. (At this pace, breeders will need to develop and Independence Day cactus for the Christmas shopping season.)

Therefore, the Thanksgiving cactus has been rebranded as a impostor stand-in for the true Christmas cactus. We won’t even talk about the Easter cactus, which just totally feels left out of the family (and yes, there is such a thing and it is beautiful).

These cacti were in cultivation in Europe by 1818 and various different species were being hybridized, probably most notably by W. Buckley.  The most notable hybrid, bred now named Schlumbergera ‘Buckleyi’ is considered to be the first actual “Christmas cactus” and associated S. x buckleyi hybrids are still grown as Christmas cacti.  Cultivars and crosses of S. truncata are the Thanksgiving cacti that have been rebranded as Christmas cacti.  They can be identified by their flattened stems (or cladodes or cladophylls) that have spiky, toothed edges and zygomorphic (now that’s a fancy word — it means that they have a two-sided, or bilateral, symmetry) flowers.  Most of the Thanksgiving cacti that have these characteristics.

W. Fitch (drew), Swan (engraved) – Bot. Mag. 66. 3717, as Epiphyllum russellianum Source: Wikimedia commons

You’ll most commonly find them in pink colors, but you can now find them in yellowish colors. The flower shape often leads to its nickname: “Zygo cactus.”

S. x buckleyi are the true Christmas cacti and form what is called the Buckleyi group.  Most of these have characteristics that come from the species S. russelliana, which was used in the early Buckley crosses. They can be identified by their rounded, less pointy cladodes and round, radially symmetrical flowers. They do have a similar growing form, but those in the know can tell the difference.

And for those following along at home, the Easter (or spring) cactus used to be considered part of the Schlumbergera genus (S. gaertneri) and then the Rhipsalidopsis genus, but now is classified as Hatiora gaertneri has radially symmetrical flowers but the cladodes are three dimensional rather than flat, elongated, and scalloped.  They have a wide range of colors, such as red, pink, and even orange.

Holiday cactus care

It’s a cactus, so it should be easy to care for – I just water it sparingly and keep it dry, right?  WRONG!

Whether you have a Thanksgiving or Christmas cactus (or an Easter one, for that matter), you take care of them the same way. Keys to their care come from their native habitat, which is not a desert but the cloud forests of costal south-east Brazil.  The high-altitude costal areas where they’re from are cool, shaded, and relatively humid with the mists and moisture rich air. They are epiphytic or lithophytic – meaning that they grow on trees and in crevices with decaying plant material rather than in the soil.  And while you don’t need to know this to grow them, the morphology of the flowers have developed to support the feeding of hummingbirds which act as their main pollinator.

Since we don’t grow them epiphytically, when we pot them we need to make sure that we provide a light substrate for them to grow and to get plenty of oxygen to the roots. Potting mixes should have a high ratio of peat or coir and even some bark or other coarse woody material.  As for watering, you’ll want to keep the soil fairly moist, rather than dry.  You’ll also want to let them dry slightly between watering, but don’t think that they like to live the life of dehydration — you do need to keep them watered.

One of the reasons that they bloom at very specific time of year has to do with light and, to a lesser extent, temperature.  They are short-day (or rather  long-night) plants, so they flower as days grow shorter (or longer, in the case of the Easter cactus) and nights grow longer.  The Thanksgiving cactus will bloom with just a little shorter dark period than the Christmas cactus, which is why it blooms in late fall as opposed to the Christmas cactus that blooms closer to when days are the shortest around the solstice.  They will also bloom better and longer if they have cooler temperatures, so keeping them in a cool area of the house is ideal.  In high light situations the cladodes will turn red.  Keeping them too dark, however, will limit growth and keep them from thriving.

Since they are short-day plants, the plants need a period of several weeks where the period of darkness at night is 12 hours or longer for their flowers to begin forming.  This occurs naturally about mid-October, but you can delay flowering by using grow lights to lengthen the day (or keep in mind that bright indoor lights can also limit or reduce blooming).  Also, don’t be alarmed if they bloom at odd times through the year.  Since daylight coming into your windows can be altered by window treatments or films, the light levels can technically be “just right” for flowering at multiple times per year.  In my old office the tint on the windows created the right conditions at least once or twice per year – one year I had a Halloween cactus and the next it was a Memorial Day cactus. 

If your cactus does not flower, you need to move it to a spot where it gets at least 12 hours of relative darkness to initiate blooms (keep away from indoor light sources or windows near outdoor lights). Hopefully, you’ll have lots of colorful blooms for Christmas…..or whichever holiday your cactus celebrates. 

Sources

Is it a Thanksgiving, Christmas, or Easter Cactus? https://www.extension.iastate.edu/linn/news/it-thanksgiving-christmas-or-easter-cactus

McMillan, A. J. S.; Horobin, J. F. (1995), Christmas Cacti: The Genus Schlumbergera and Its Hybrids (p/b ed.), Sherbourne, Dorset, UK: David Hunt

Hydroponics, Aquaponics, & Aeroponics, Part Deux

Last month I shared some basic info on the major techniques for growing plants without soil, namely hydroponics, aquaponics, and aeroponics.  With such interest in these topics, I thought it would be good to dive a little further into the technologies used.  I’ll provide a bit of basic information about each type of system used for production and provide some resources for further technical reading if you’re interested in learning more. For some simple diagrams of the systems, check out this link (we don’t know if we can “borrow” the images, so we didn’t copy them over).

DEEP WATER

“Deep” water may be a bit of a misnomer, as it usually brings to mind thoughts of mysterious sea creatures living in the dark depths of the ocean.  Technically, the “deep” water can be just a few inches, as it is deep in reference to other methods.  This is perhaps the simplest and least expensive of the systems and can be a great entry point for beginners.

For deep water culture, the nutrient solution is held in a large container with some sort of floating support holding the plants.  The container is at least a few inches deep and holds a relatively high volume of water.  There are some containers that are designed for deep water hydroponics, but repurposed containers will work as long as they are food safe (meaning that they do not leach or break down).  Large plastic totes or even plastic buckets can be used.  As for supporting structures for plants, Styrofoam is the most common.  There are cell trays made of Styrofoam that are commonly used in production of small crops (or for growing transplants, which is a common use of this technique).  Foam boards with holes to hold pots can also be used.  Back when I was in grad school we developed hydroponic systems in my plant propagation class using foam insulation boards floating in large plastic totes.

One thing that you have to keep in mind for deep water culture is the need to incorporate oxygen into the system.  We often talk about the issue of overwatering houseplants and how it can damage roots  due to hypoxic, or low oxygen, situations.  Imagine how roots growing only in water would create situations for poor root and plant growth.  In all the other systems water flow helps incorporate oxygen into the water.  In deep water, there is no moving water and therefore no air incorporation.  The most common tool used for this, especially for small systems, is an aquarium air pump and air stones that help create bubbles in the system.

One benefit of this system is that it has a low level of risk when it comes to system failure.  There are few moving parts to break down and loss of electric doesn’t result in roots drying out due to loss of water flow.

EBB & FLOW

Ebb and Flow troughs in an aquaponics system. Note the floating styrofoam rafts. (I did research in this system during my master’s program.)

These systems, also called flood and drain systems, are one step of complexity above the deep water systems by introducing water flow.  Plants can either float as in deep water culture or be held in media that fills the container.  While many containers can be used, the most common are longer channels that promote water flow from one end to the other.  This system also introduces a reservoir of some sort that holds excess nutrient solution and a pump to deliver it to the container.  The level of water in the container is controlled by a raised drain pipe where solution exits the system back to the reservoir.

The DIY system I build using gutter with the Rwandan students (mentioned in the first installment on hydroponics) is ebb and flow.  The drain from the gutters is a few inches high within the channel, so the water raises those few inches before it drains out.  Some producers use long channels the width of those floating cell trays to grow plants in a relay fashion, planting them on one end and move them along as new rafts are added until they are harvested on the other end.

This system is common not only in hydroponics, but aquaponics as well.  Instead of a nutrient solution reservoir, the water from the tank(s) holding the aquatic stock (commonly fish, but could also be crustaceans like shrimp) is pumped into the plant channels and flows back into the system.  Systems may be based on continuous flow into and out of the system, but most commonly a timer is used to have multiple periods of flow and rest mainly as a means to reduce power usage.

NUTRIENT FILM TECHNIQUE (NFT)

This system evolved one more step above ebb and flow by limiting the volume of water used in the system.  Here, water is pumped from the solution reservoir to shallow channels where plants are held in pots or blocks of inert media such as rockwool.  Roots are not submerged in water, but instead grow within a thin film of solution that flows almost continuously through the system.  These channels have a slight slope where the end with the drain is a little bit lower than the end where the water enters.  The slope can be adjusted slightly to affect the speed of the water through the system.

This system is becoming common in production of leafy greens and herbs because it uses a much smaller volume of water.  But that small volume of water also presents a risk.  If there is a power failure or a clog in the tubing that delivers water to the system the roots can very quickly dry out and crops die, especially in situations of high heat and light.

DRIP SYSTEMS

Dutch bucket method for trellised crops

Perhaps one of the most commonly used systems across the world due to their simplicity, drip systems could be compared to a drip irrigation system used in the field.  Drip emitters are used to supply nutrient solution to plants in containers containing an inert media such as peat, coir, perlite, or grow stones. The containers can be pots, buckets, or bags/blocks of the media and are most commonly placed on the floor of the greenhouse or growing location with gutters to collect the solution that flows through the containers. A common method is using long, narrow bags filled with coir or other media referred to as the slab method.  Another common method, called the Dutch bucket method, uses buckets with drain holes in the bottom, commonly placed on a greenhouse floor.  Water trickles down through the media and roots and leaves the system through the bottom of the container.

Systems vary in the collection of the used solution.  Some may collect the solution that flows into the gutter and collect it in a reservoir to be reused, however some systems may allow the solution to flow out as waste.  These differences depend on the needs of the producer, available resources, and local regulations.

One of the comments that we got on my first article was about people growing container plants could technically consider it a form of hydroponics.  That might be a bit of a stretch, but you could technically consider growing container plants in soil-less media as drip or flow through hydroponics if you provide all of the nutrients through soluble fertilizers in the water.

WICK SYSTEMS

Typically used for small scale production, wick systems are one of the simple ways to grow plants without soil in terms of technology.  In this system, a passive wick uptakes nutrient solution from a reservoir and pulls it into the media (usually absorbent itself).  This wick could be a true wick, like a string made of absorbent material that inserts into an individual pot or it could be a mat made of absorbent material that pots or trays sit atop.

I’ve seen this commonly used perhaps not strictly in hydroponics, but for watering individual plants like African violets where yarn or twine is inserted into a drain hole in the pot and sits in water.  Technically this could be hydroponics if the media doesn’t contribute nutrients to the plant and they are all contained in the water instead.

KRATKY METHOD

This is probably the simplest of the methods and is used primarily by small scale producers and home growers.  It is similar to the deep water method in that there is no flowing water, but it is even simpler because there isn’t even an air bubbler.  In this method, plants are grown in large containers or buckets and the structure that supports them is fixed to the top of the container rather than floating.  As the growing solution is used up, the level of solution in the container decreases.  This creates a zone where the roots are exposed to air, providing the oxygen that the roots need.  The solution is kept at a level where at least the bottom portion of the roots are submerged in the nutrient solution.

AEROPONICS

Probably the most complex or technical system, aeroponics supplies water and nutrients to plants through a mist or aerosol emitted through pressurized nozzles.  The roots hang in a chamber without media and are misted every few minutes with nutrient solution.  The excess solution drops to the bottom of the chamber and is reused.  This system uses very small amounts of water, which can be beneficial for growing in dry areas but also creates a potential risk if the system or power fails.  Just like the NFT system, any prolonged period with out water will quickly result in plant damage or loss.  Beside power loss, this systems is also prone to clogged emitters, since the pressurized nozzles rely on very tiny openings to pressurized the solution.

Keep in mind that several systems that are sold for home or small scale production that are labeled as aeroponic, such as AeroGarden and Tower Gardens, don’t technically use aeroponics to grow since the solution isn’t applied as a mist or aerosol.  I would say they operate more like a vertical NFT system where water flows over the roots as it travels down the chamber.

RESOURCES

Hydroponic Greenhouse Production Resources – UMass Extension

Introduction to Hydroponics – Johnny’s Seed

All You Need to Know to Choose a Hydroponic System – Upstart Farmers

How to Start Growing with the Kratky Method – Upstart Farmers

DIY Hydroponics: Going soil-less at home and abroad

It seems that as interest in gardening grows, especially among younger generations, interest in different techniques that home gardeners use and different plants they grow are also on the increase.  You see the old standbys like straw bales and containers emerge.  Terraria, succulents, and air plants are having their moment.  And all kinds of technology driven indoor growing systems are all over the web, mostly hydroponic, but some aeroponic and aquaponic as well (we’ll talk about the difference in a bit – if you’re just here for that, skip the first 2/3 of the article).

I had been thinking about getting one of those new techno aeroponic growing systems as a demo for my office as a discussion starter for those interested in controlled environment growing whether on the homework commercial scale.  There is a general interest and need for basic education for hydroponics and aquaponics in the area that I hope to build extension programming around, so having something at the office could provide some interest from walk-in and social media clients.   I had dusted off a first generation AeroGarden that I found in the storage shelves in the office storage catacombs and set it up in my office.  It is a far cry from the new models I saw in those online ads that are outside of my budget for “toys to show off at the office.” It doesn’t have nice LED lights or connect to my phone via Bluetooth like the fancy new models.  Given its age, it produces more noise and heat than the lettuce and herbs I’ve tried to grow in it.  Maybe I’ll be able to get one of the fancy models one day.

Then I remembered a book that an urban ag friend of mine had written on building DIY hydroponic systems from common building materials and resolved to not only build a system, but incorporate it into my programming somehow.  The book, appropriately titled “DIY Hydroponic Gardens: How to Design and Build an Inexpensive System for Growing Plants in Water” by Tyler Baras shares plans for building a variety of types of hydroponic systems using basic building materials like gutters and lumber, drip irrigation tubing and fittings, and various other bits and bobs.  Tyler had been a featured speaker for the West Virginia Urban Agriculture Conference that I started and hosted when I worked for WVU Extension, so the book was on my radar – I placed an order.  (Note: I don’t get a kickback for sharing the book – just sharing a good resource that happens to be from a friend.)

Teaching Hydroponics to an Unlikely Audience

Image may contain: 3 people, including John Porter, people sitting, outdoor and nature
Learning traditional weaving methods using banana leaves. Banana leaf weaving is a common industry in rural Rwandan villages that allows women to provide modest incomes for their families.

As luck would have it, I had an opportunity to put the book, and my DIY hydroponic skills, to the test.  Our university does quite a bit of work with and in Rwanda and in May I had the opportunity to travel to Rwanda as part of a study abroad program with my Ph.D. advisor.    Rwanda is a very small country, just under the size of Massachussets, with a very big population by comparison – 12 million vs 7 million!  Feeding that many people is a struggle, and even though Rwanda produces a lot of produce (and more lucrative export crops like coffee and tea), it still imports a lot of its fruits and vegetables.  We were studying how innovation spreads in rural areas, and just before our trip I found a news article sharing that there would be an upcoming $8M USD ($8B RWF) investment in hydroponics in the country in order to increase production on the limited amount of land available.

In June I was scheduled to teach a group of Rwandan exchange students that are part of a sponsored program at the university, and remembering the planned investment in hydroponics I planned to add DIY hydroponics to the curriculum.  This is fitting, since most small-scale operations would rely on finding what materials would be locally available.  While the operations started by the investment would likely bring in “real” hydroponic systems, if small scale producers want to use the technology or if individuals want to build skills, they’re going to have to use what is at hand.

UNL CUSP Scholars students from Rwanda build a DIY Hydroponic System

Planting leafy greens and strawberries in the hydroponic system.

 

 

 

 

 

 

 

 

It was interesting teaching an audience who were interested in learning about the new technology, but have little experience or general knowledge on the subject.  Even more interesting was the fact that many of the students had not used or even seen some of the basic power tools we used in building the system.  I’m no shop teacher, but in the end the students not only learned a little bit about hydroponics and hydroponic systems, but also some skills using tools that they can apply in other applications.

Proudly showing off the team’s vertical hydroponic system.

 

 

 

 

 

Hydroponics, Aeroponics, & Aquaponics – Oh My!

Earlier I mentioned that there are differences between hydroponics, aeroponics, and aquaponics.  In some ways, they use similar basic setups.  All are based on soil-less growing using an inert media to support plants, supplying nutrients and water directly to the plant roots, and providing light to the plants using either natural sunlight or supplemental lighting.  Differences come from the source of plant nutrients and from how they are delivered to the plant.  I thought I’d take a few minutes to talk about the basics of each of the techniques so you can understand the differences just in case you want to buy or build your own system.  If there’s interest, I hope to focus on hydroponics and controlled environment agriculture over my next few blog posts – tell me what you’re interested in learning.

Most people are familiar with the concept of hydroponics.  This technique relies on roots being submerged in a nutrient-rich solution where the nutrient content is engineered from a variety of mineral sources.  There are a variety of different systems (that will hopefully be the subject of an upcoming blog) where the root zone interacts directly with the solution.  In some cases, roots are submerged in a large volume of solution while in others a film or shallow stream of water flows through the root zone.  Systems where roots are submerged in the solution may simply be a large reservoir where the plants float on top where systems relying on flow may involve a pump.  Movement of water adds another plant need -oxygen, which is required for respiration by the roots.  In systems where there is no flow, air is often pumped in to provide oxygen.

Most flowing systems are recirculating, where the solution returns to a reservoir and is pumped back into a reservoir to be reused.  While it may seem counterintuitive, these recirculating water based growing systems have been touted as production methods that conserve water.  That’s why some of the leading hydroponic production and research comes from areas of the world where water is scarce. Less common are flow through systems where water and nutrients are not recaptured but discarded after initial use.

Aeroponic systems have much of the same basic setup but instead of the roots interfacing directly with water solution it is applied as a pressurized mist.  These systems generally use a much smaller volume of water, but there are some drawbacks.  Failure of the system, such as an electric outage or clogging of the nozzles that pressurize the mist (which is a common occurrence) can quickly result in plant failure since roots can dry out quickly.  Several systems that are sold commercially that market themselves as aeroponic, such as the AeroGarden or Tower Gardens, are more similar to a flowing hydroponic system than a pressurized mist aeroponic system.

The plant growing structures of aquaponics are similar to those of hydroponics, with the addition of larger reservoirs to accommodate the addition of aquatic livestock such as fish (or sometimes crustaceans).  The waste produced by the stock provide the nutrients needed by the plants rather than an engineered nutrient solution.  These systems require having the technical knowledge to meet the needs of the aquatic stock and balancing those with the needs of the plants.  The addition of the aquatic stock also introduces a microbiome of bacteria and fungi, many of which are required for animal health but can also introduce pathogens that can negatively affect human health.

Are you interested in learning more about these systems?  What do you want learn about in hydroponic or other systems? Let me know in the comments and I’ll try to base some future articles on what our readers are interested in.

GPs at the Tradeshow: Looking for snake oil and finding…..the dirt on tillage

The Annual Meeting and Professional Improvement Conference of the National Association of County Extension Agents is that one time of year where extension agriculture professionals gather to share ideas, give talks, network, and let their hair down. The name of the organization is a bit outmoded: many states no longer call their extension personnel agents, but rather educators, experts, professionals, area specialists, and the like. Most aspects of agriculture are included: from the traditional cows and plows of animal science and agronomy to horticulture and sustainable agriculture (I’m the outgoing national chair of that committee). There’s also sharing on agriculture issues like seminars on engaging audiences about genetic engineering, teaching and technology like utilizing social media and interactive apps, and leadership skills.

It is the one time every year or so that Linda Chalker-Scott, grand founder of the Garden Professors, and I get to hang out. If we’re lucky we’ll meet up in some sessions, chat in the hallways, or grab a drink. But one of our favorite conference activities is taking a turn around the trade show floor. This is where companies and organizations are vying for the attention of extension educators to show them their newest equipment and products….we are, after all, the people that share growing and production information with a great number of potential clients across the country.

Since the organization runs on money, almost no company that comes calling with the money for a trade show spot is turned away. This means that the products may or may not stand up to the rigors of scientific accuracy. In years past we’ve found snake oil aplenty, like magical humic acid that is supposed to be this natural elixir of life for plant growth. The only problem is that humates don’t exist in nature and there’s little documentation of any effect on plant growth. The product that was supposed to be this magic potion was created from fossil fuels and no actual peer-reviewed research was offered by the company – hardly convincing. There were magic plastic rings that supposedly acted as protective mulch around mature trees and could slowly release water, except that mature trees don’t really need protective mulch and the amount of water would be negligible to a tree that size. So will we be smiling or scowling when we’ve made our way through the trade show.

Right off we set our sites on a company starting with “Bio”, which can be a good indicator of questionable rationale. That lit up the first indicator on our woo-ometer. Beneficial bacteria you apply to plants/soil: woo-ometer level two. So LCS and I engaged the representative. Asking about the product and what it does. We learned about their different products that could help increase the rate of decomposition of crop residues in farm fields, of turfgrass improvement, increased crop production, and treatment of manure pits on dairy and hog farms (which, if you’ve ever experienced one, you’d know would benefit from any help they can get in terms of smell).

Most of the products like this give vague descriptions of the beneficial bacteria it contains. They’re akin to compost teas that can have any number of good, bad, and downright ugly bacteria and fungi in them.  Since you don’t know what’s in these products, any claims on soils or plants are suspect at best. However…our rep went on to tell us that the company created blends of bacteria from specific strains that had been researched for their effects on decomposition, soil nutrient availability, and plant growth. There was a brochure with the specific bacteria listed, along with studies the company had conducted.

We asked about peer-reviewed research, which is our standard for evidence here at the GP, and while he had no results to share he assured us that university-led research is currently in the works. And as we’ve stated in regards to applying of beneficial bacteria to soil – while there’s little evidence showing the effectiveness of applying non-specific bacteria to plants, using directed applications of specific bacteria which have been tested for specific functions are supported by research. So our woo-meter didn’t fully light up. We reset it and continued the hunt.

We scoured the rest of the trade show and found one other soil additive that lit up the first lights of our woo-meter, but the rep must have been out for lunch so without anyone to talk to we couldn’t confirm woo or no-woo.

However…..we did find something spectacular! The local employees of the USDA NRCS (Natural Resources Conservation Service) had an interactive demonstration of soil, specifically showing the benefits of reducing or eliminating tillage. The NRCS works with many farmers to incorporate conservation practices on farms, including no-till production, by providing technical assistance, farm plans, and even grants, cost-share, and easement programs. Many farmers have benefitted from their grant for season extension high tunnels (which are seen as a soil conservation technique, since they shelter soil). We were so enamored with the demonstration, we asked them to do it again…so we could record it. So, for your viewing pleasure check out the video below where you can see how well no-till soil holds its structure while tilled soil falls apart. This effect is from the exudates from all the beneficial microbes in the soil that act like glue to promote good soil structure. We’ll let the video speak for itself……

So not only does the trade show get a smile instead of a scowl from us, but also two thumbs up! Either there has been some weeding out of the trade show sponsors, maybe the snake oil salesmen didn’t get the traction they were hoping for at the conference, or hopefully some of these companies have failed to reach an audience with their pseudoscience.

 

Testing, testing, 1-2-3: Trialing new plants for the home garden

How do you know that plants will do well in your garden?  Do you research the types of plants for your region, study different cultivars, and select only things that have been proven to do well for your conditions?  Or do you buy what catches your eye at the garden center, plant it, and then see what happens?  I used to joke that my home garden was a horticulture experiment station, since I’d try all kinds of random plants or techniques and see what works for me.  Now, I get to do that as a fun part of my job through the All-America Selections (AAS) program. You’ve likely seen the AAS symbol on plants or seed packets at the garden center or in catalogs.  Heck, you may even have them in your garden (and not know it).  I compare it to the “Good Housekeeping Seal of Approval” that you used to see on appliances, cleaners, etc. The AAS program is a non-profit started in the 1930’s with the goal of evaluating new plants so that home gardeners can purchase high quality seeds and plants and to assist the horticulture industry in marketing innovations from their breeding programs.  You can read more about AAS and its history here.

A few weeks ago I traveled to Chicago for the All-America Selections (AAS) Annual Summit to receive their Judge Ambassador Award.  I had signed up a few years ago to be a trial site for edible crops for AAS.  The following year I talked my colleague Scott into signing up as a judge for their ornamental trials.  The fun thing about the program is that we get to grow all kinds of vegetables, fruits, and flowers that aren’t even on the market yet.  We get to see how well they grow compared to similar plants and rate them on a number of factors including growth habit, disease resistance, and performance plus flavor (for edible crops) or flower color/form (for ornamentals).  It can be hard work, but it is rewarding to help identify true plant innovations and to see your favorites be announced as winners.

How the testing works
While the AAS Trials may not have the rigor of academic crop research, I do appreciate the procedures in place that provide objective and high standard results.

Breeders, developers, and horticultural companies submit their new plants that are planned for future introduction to the board of AAS for consideration in the trialing program.  During the application process, novel traits of the plants are identified to ensure that the plant offers something new and exciting – these are the traits that judges will observe and score.  The board reviews the application to determine if it fits within the program rules.

Planting the vegetable/fruit trials.

One great thing about the program is that trial judges are professional horticulturalists from universities, seed companies, botanical gardens, etc. – they’re people who know how to grow things and know what quality plants look and act like.  There are trial sites all around the country, providing for replication and generalizeable results for most regions of the country. The conditions plants are grown in also vary by location.  My trial is at a farm where management is minimal.  When we were at the summit we visited the trial gardens at Ball Horticulture which looked much more maintained and pampered compared to mine.  This gives data on a variety of maintenance levels as you’ll find in home gardens – some gardeners are very conscientious about maintaining their plants and others have a more laissez faire approach.  In order to win as a full national AAS winner, the plants have to perform well across the country in all these different situations.  Sometimes those that perform well in a few regions but not the others will be designated as regional winners.

Second, the tests are blind.  This means that we do not know what the exact plant is, who the breeder or seed company is, or any other info other than what type of plant it is.  To the judge, each entry is just a number.  It could be from a seed company you love (or hate), your best friend, the breeder who was your advisor from grad school, etc.  This makes the results fair and reduces the chance for bias toward or against a plant based on its origins.  The ratings are just based on the plant.

Another part of the trial is comparison.  It is one thing to grow a tomato plant and say “yep, that’s a good tomato.”  Its another to grow a tomato and compare it to similar cultivars to say “yep, that’s a good tomato….but it is better than what’s already available on the market.”  The goal of the program is to show how new plants have merit over older plants.  We only need so many new tomatoes (and let’s face it, there are lots of new tomatoes – we test WAY too many in the AAS process for my liking).  The board of AAS judges reads the entry info from the new cultivar being tested and selects plants (usually two) to compare it against.  If the trial is a yellow cherry tomato, it will be grown and tested alongside other yellow cherry tomatoes.  The scoring is based on whether its performance or taste is as good as or better than the comparisons.  If most judges don’t rank it as “better” then it has no chance of winning.

Confidentiality and Proprietary Plants

The fact that the testing is blind, paired with the fact that results of “failed” tests are not released, lends itself to confidentiality.  Another important factor about the testing is the proprietary nature of the tests and test sites.  These are new plants that haven’t been introduced to the market (except for the case of perennial trials) and are usually for proprietary or patented plants.  Test sites should have some sort of control over who enters them and signs prohibiting the collection of seeds, pollen, or cuttings are placed at the site.  Believe it or not, the world of plant introductions can be dog-eat-dog and cutthroat.

So what if it doesn’t win?

One of the cool things about the test is seeing the announcements of the winners early the following year.  You see the list of plants and think back to what you grew the previous season.  If often find myself thinking “oh yeah, I remember that plant, it did really well” and sometimes even “how did that win, it did horrible for me.”  This is a good reminder that we can’t base generalized garden recommendations on anecdotal evidence.  What did well for me may not work for someone else and vice versa.  All the results from the test sites go together to provide a general view of the plant performance.  It will do well for some and not others.

So if most of the judges rank the crop as not performing, looking, or tasting as good as the comparisons the plant doesn’t win.  And that’s it.  Due to the confidential nature of the testing you won’t know that it failed the test.  Even I won’t know that it failed the test. It will likely go on to market without the AAS seal where it will face an even tougher test – the test of consumer demand.  Of course, many people may grow it and be successful, and some may grow it without success.

What are the AAS Winners and how do I find them?

There’s a list of plants announced each year through the AAS website and social media channels.  You can find a list, in reverse order of winning (meaning most recent first) on the AAS Website.  The site also has a searchable database if you’re looking for a specific plant.  Since these plants are owned by lots of different seed companies and breeders, there’s also a retailer listing on the site.  The AAS program also supports a number of Display Gardens across the country, including botanical gardens, university gardens, and others where the public can see the most recent winners growing.  Here in Omaha we maintain a display garden for the ornamental plants at our county fairgrounds.  We also have our on-campus garden which is used for our TV show Backyard Farmer (the longest running educational TV program in the country, BTW) which serves as a display garden for both ornamental and edible crops.

I recently shared the AAS Testing Program with the local news here in Omaha. Check it out:

 

Some of my favorite recent AAS Winners
Pak Choi Asian Delight AAS WinnerAsian Delight Pak Choi – this was planted in May and didn’t bolt.  We were still harvesting it in October.

 

 

 

Pepper Just Sweet - 2019 AAS Edible-Vegetable Winner

Pepper Just Sweet – these plants were big and healthy even when everything else was struggling.  The peppers were delicious.

 

 

 

Potato Clancy - 2019 AAS Edible-Vegetable Winner - The first potato grown from seed!

Potato Clancy – potatoes….from seed!  Just fun!

 

 

 

 

Pepper habanero Roulette - 2018 AAS Edible - Vegetable WinnerPepper Habanero Roulette – All of the fruity sweet, none of the heat.  A fun heatless habanero.

 

 

 

Dianthus Interspecific Supra Pink F1 - 2017 AAS National Winner - This compact, bushy plant blooms prolifically with novel mottled pink flowers sporting frilly petal edges that hold up even in summer heat and drought.Dianthus Intraspecific Supra Pink– A reblooming, prolific Dianthus with interesting ruffled flowers.

 

 

 

Eggplant Patio Baby – container sized eggplant with mini fruits perfect for cooking or roasting whole.

 

 

 

Ornamental Pepper Black Pearl 2006 - AAS Flower Winner - Black Pearl is a handsome plant with black foliage.Ornamental Pepper Black Pearl – Cute purple flowers lead to these shiny pepper pearls.  Love the black leaves, too.

To Fertilize, or Not to Fertilize, that is the question

You see a bright shiny package at the garden center saying that it can help you have the most bountiful garden ever, the greenest lawn in the neighborhood, your plants will have miraculous growth, or it will supply every element on earth to make sure that your plants are living their best life. It’s got what plants crave….It’s got electrolytes! You reach out to grab that package and ……. Woah!  Pump the brakes!  Do you know if your plants even need to be fertilized?  Are you just falling for that shiny marketing, or do your plants really need added fertility to grow?

It turns out that many gardeners add fertilizer out of habit or because a shiny package or advertisement told them they needed to do it.  The fact is, though, that you may or may not need to add fertilizer to get your plants to grow healthy.  It is actually more likely than not that the level of nutrients in soil is perfectly adequate for healthy plant growth. And guess what, there really is a way to know what plants crave…or at least are lacking: A soil test.

We here at the Garden Professors (and those of us who work in extension) often get questions or hear comments about gardeners adding fertilizer or random household chemicals and items to their plants and soils with no idea what they do or even supply.  They’ll throw on the high powered 10-10-10, the water soluble fertilizer, rusty nails, or even (shudder) the oft mentioned Epsom salts because it is just what they’ve been told to do.

A few months ago, my GP colleague Jim Downer talked about why to amend soil– focusing mainly on organic material and a little bit of fertility.  In this article, I’m going to share some how and what: what plants need in terms of nutrients, how to determine what nutrients you need to add, what you can use for increasing fertility (conventional and organic), and how to calculate how much fertilizer to add.

What plants really need

Plants have a number of essential plant nutrients that they need from the environment in order to properly grow and function. Hydrogen, carbon and oxygen are all important, but are not something that gardeners have to supply since they are taken in by the plant in the form of water and carbon dioxide (unless you forget to water your plants, like I sometimes do — but death will occur from dehydration well before lack of hydrogen).

There are six soil macronutrients, which means that they are used in larger amounts by the plants. These include nitrogen, phosphorous, and potassium, which form the basis of most common fertilizers that have those magic three numbers on them (example: 10-10-10). Those three numbers indicate that the fertilizer contains that percentage of the elemental nutrient in it. For this example, the fertilizer contains 10 percent nitrogen, 10 percent phosphorous, and 10 percent potassium.  The other three soil macronutrients are magnesium, sulfur, and calcium.  Depending on your location, your soil may be abundant or deficient in these nutrients, especially magnesium and calcium.  Sulfur is commonly released during decomposition of organic matter, so it is usually present in sufficient amounts when soil is amended with (or naturally contains) organic matter.

If a soil is deficient in a nutrient that a plant requires it is usually a macronutrient since plants use them at higher levels.  However, deficiency is still unlikely in most soils unless there is a high volume of growth and removal, such as in vegetable gardens and annual beds (or if you’re growing acres of field crops like they do here in Nebraska).  These are also the nutrients that are most common on soil tests, since they are the ones that are used the most by plants.

Soil micronutrients are needed in much smaller amounts. Those nutrients are boron, copper, chlorine, manganese, molybdenum, and zinc (remember the periodic table?). These are also usually supplied from organic matter or from the parent soil material so deficiency is even less likely than for macronutrients.  Tests for these aren’t usually part of a basic soil test, so if you suspect you might have a deficiency you might have to get a specialized test.  There are some basic physiological signs of deficiency that plants might exhibit in response to specific deficiencies, but their similarity to other conditions make it an imprecise tool for diagnosing a deficiency.

Compost is a good source of nutrients, especially micronutrients (as we’ll read later).  Using compost alone may be sufficient for many gardens, such as perennial beds.  However, higher turnover and higher need areas like vegetable gardens may need supplemental fertilization beyond compost.  That’s where the soil test comes in.

What’s on the menu….interpreting soil test results

If you’ve had your soil tested by a lab (which is recommended, since it is much more precise than those DIY test kits), you’ll get results back that give you the level of nutrients in your soil and usually recommendations for how much of each nutrient you need to add to the soil for basic plant health.  This is a general recommendation that is common for most plants, which is generally sufficient for average growth.  If the test says that the nutrient levels are normal, you don’t have to add anything….I repeat….YOU DON’T HAVE TO ADD ANYTHING.  If it says you need one nutrient of the other you’ll need to add it to your garden or around the plant.  As we’ve said before, disturbing the soil as little as possible is best, so if you’re using a fertilizer product aim for one that you can broadcast on top of the soil or is water soluble.  This goes for compost as well – try to apply it to the top of the soil and it will incorporate over time.

Image result for soil analysis reportYour soil test results will usually tell you to add nutrients in pounds per a certain square footage.  In the example pictured, there’s a recommendation of 3.44 lbs of Nitrogen per 1000 square feet.  That number is for the actual nitrogen, and since different nutrient sources have different amounts of nitrogen you’re going to have to do some math to figure out how much fertilizer you need per 1000 square feet and then multiply that by how many thousands of square feet you have.

I’ll note here that soil labs do not usually test for nitrogen due to the variable nature of nitrogen in the soil and the lack of affordable or reliable tests.  Nitrogen fluctuates widely over a short period of time and is not as persistent in the soil as other elements due to plant take-up, microbial action, and weather conditions.  Nitrogen recommendations are usually made based on the crop indicated for the test and may be informed by the levels of other nutrients.

Let’s say that I’m using an organic fertilizer product I purchased at the garden center and the nutrient analysis is 4-3-3 (these numbers are standard for organic nutrient sources, which have lower nutrient levels than conventional fertilizers).  That means that for every 100 lbs of that product, 4lbs are nitrogen, 3 are phosphorous, and 3 are potassium.  My (hypothetical) garden is 10ft by 20ft, which is 200 square feet.

So we divide 200 by 1000 to get .2, which represents that my area is 20% of the area listed on the recommendation.  If my garden were 3500 square feet, then that number would be 3.5.

Next, multiply the Nitrogen recommendation of 3.44 lbs by .2.  This give me 0.688.  This tells me that I need .688 lbs of nitrogen to amend my 200 square feet.

So I just need to weigh out .688 lbs of the fertilizer, right?  Nope – we have to account for the fact that my fertilizer is only 4% nitrogen- only 4 lbs out the 100 lb bag.  We can estimate amounts by figuring out how much nitrogen is in smaller amounts of the fertilizer.  Since we know that 100lbs has 4lbs of N, then 50lbs has 2lbs of N, and 25lbs has 1lb of N.  If I want to get a more precise amount of fertilizer poundage to get my .688 lbs of N, then we divide the pounds of N needed by the decimal percentage of N in the fertilizer.  So that would be .688 / .04, which gives us 17.2 lbs of fertilizer.

Now, considering that the bagged product that I bought is $25 for 8lbs, I may want to reconsider using it for this application…unless I enjoy throwing my pearls before swine or I’m fertilizing my money tree.

If you do the math, you’ll note that this fertilizer will add more than the recommended amount of phosphorus and potassium.  You’ll either need to decide if that is acceptable or if you need to find another source of nutrients.

If you’re not using a prepared fertilizer product but rather an organic source of nutrients, you can still calculate how much to add to get to the recommended amount.  The following are some good lists of nutrient ranges of organic materials:

https://extension.psu.edu/using-organic-nutrient-sources

https://vegetableguide.usu.edu/production/soil-nutrient-water-management/organic-nutrient-sources

A note about pH

Another thing your soil test will tell you is the pH of the soil.  In general, plants prefer a soil pH just on the acidic side of neutral (between 6.0 and 7.0).  There are plants that prefer different pH levels – such as blueberries and azaleas and their need for a more acidic soil between 4.5 and 5.2.  Changes in pH affect the availability of nutrients to plant by affecting ionic bonds of the elements.  For the most part, the nutrients are more available at that neutral pH.  You’ll note that iron is more available at lower pH levels, which is why those acid-loving plants grow better at lower pHs – they’re heavier iron feeders.

If your pH is extreme in one way or the other, you’ll either need to find plants that thrive at that level or adjust the pH if that isn’t possible.  To raise pH in acidic soils the most common method is application of lime.  To lower pH, you’ll need something high in sulfur.  For more information, visit https://articles.extension.org/pages/13064/soil-ph-modification .

Having a philosophical moment in the garden

Ripe for the picking: Which fruits keep ripening after harvest?

“Will my peppers continue to ripen? How about my eggplants?”  It is common knowledge to most gardeners (and home cooks) that tomatoes will ripen on the kitchen counter, as will bananas and several other fruits.  You know that one day your bananas look perfectly ripe and the next they’re a brown mush But does this work for all fruits?   We often get questions about whether specific fruits will continue to ripen after picking.  And the answer is….. it depends.

How green were my peppers…

One of these fruits is not like the other

The answer as to whether a fruit will continue to ripen after harvest depends on which one of two groups it falls into.  These groups are climacteric and non-climacteric fruits.  In short, climacteric fruits are the ones that will continue ripening after harvest and non-climacteric fruits are ones that don’t ripen after harvest.

Image result for ethylene

This refers to the “climacteric phase” of fruit ripening where there is an increase in the gaseous plant hormone ethylene and an increase in respiration, which drives the ripening process. It is the climacteric fruits that will keep ripening once they’ve been harvested, thanks to ethylene.  The only stage of maturity for non-climacteric fruits after harvest is…..compost.

 

As long as you’re green, you’re growing.  As soon as you’re ripe, you start to rot. -Ray Kroc

Almost all fruits produce ethylene, but non-climacteric fruits produce them at much lower levels and do not rely upon it as the main driver of ripening.  I’ll go into a bit more detail in a bit, but first – which fruits are climacteric and which are non-climacteric?

 

Common Climacteric Fruits Common Non-Climacteric Fruits
Apple Brambles (raspberry, blackberry, etc).
Apricot Citrus (oranges, lemons, limes, etc.)
Avocado Eggplant
Banana Grape
Blueberry Melon (including Watermelon)
Cantaloupe / Muskmelon Pepper *
Cherry Pumpkin
Fig Squash (summer and winter)
Kiwi Strawberry
Mango
Papaya
Pawpaw
Peach
Pear
Plantain
Plum
Tomato
Cherry
*Some evidence of climacteric ripening in hot peppers

Image result for avocado ripe meme

The ripening process

Ripening is genetically programmed – meaning that it is highly dependent on processes that are regulated by genes and it specific to each species.  Parts of the process are started and stopped due to the transcription and translation of genes, which are in turn controlled by signals such as chemical compounds, physiological stages of the plant, climate, and so on.  These ripening processes have a lot of end results – sugars accumulate in the fruit, pigments develop, some compounds that have pleasant flavors develop while others that are unpleasant are broken down, some of the pectins in the fruit break down to make it softer, and on and on.

Tomatoes – the classic climacteric fruit

Getting close…

 

 

 

 

 

 

 

Research shows that ethylene, the simple little gaseous hormone plays a crucial role in the ripening of climacteric fruits by altering the transcription and translation of genes responsible for ripening.  Ethylene is the dominant trigger for ripening in these plants.  Ethylene receptors in the cells are triggered by the presence of the gas which leads to cascade effect.  This is why ethylene can be introduced from other fruits to trigger ripening in fruits that aren’t ready to ripen.  If you’ve heard of the tip to put an apple in a bag full of some other fruit to get it to ripen, it actually works – as long as it is a climacteric fruit.

The same ripening processes happen in non-climacteric fruit as well, but they are not dependent on the presence of ethylene.  In fact, these pathways are also present in climacteric fruits – the ethylene-dependent processes are just the dominant (and faster) way that they ripen.

Controlling ripening

The dependence on ethylene for a vast majority of fruits to ripen has been used by farmers and the food industry for a long time to keep climacteric fruit more stable for shipping.  These fruits are harvested “green” before they ripen and shipped unripe since they are much firmer and much less likely to get damaged in transit.  These days, bananas, tomatoes, and other climacteric fruits are likely to be given a treatment that temporarily inhibits the ethylene response before harvest or shipping to extend their shelf life further.  Once they’re close to their final destinations they’ll either be allowed to ripen on their own or given a treatment of ethylene to speed back up the ripening process.

What we gain in shelf-life and reduced food waste we do lose in a bit of flavor.  Since the fruits are no longer attached to the plant when they ripen they don’t have the chance to transport more sugars and flavor compounds from the mother plant.  So “vine ripened” fruits do have a bit more sweetness and flavor than those that are picked green.  Having just gotten back from Rwanda, a country where bananas are a common staple food I can attest that the ones that ripen on the plant are much sweeter than those we get shipped in to the US – you know, the ones that will ripen next week sometime if you’re lucky.  There were even some in our group that don’t care for bananas here that loved the ones we had at breakfast every morning.

Grapes must stay on the vine to ripen

One possible direction for biotechnology is the engineering of plants to alter or eliminate the ethylene ripening response to reduce food waste and spoilage.  Since many genes that are responsible for ethylene production such as enzymes that catalyze the production of ethylene precursors, or proteins that serve as ethylene receptors have been identified, work is being done to develop delayed ripening by altering or knocking out these genes in a variety of crops.

Sources

Alexander, L., & Grierson, D. (2002). Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening. Journal of experimental botany53(377), 2039-2055.

Pech, J. C., Bouzayen, M., & Latché, A. (2008). Climacteric fruit ripening: ethylene-dependent and independent regulation of ripening pathways in melon fruit. Plant Science175(1-2), 114-120.

Lelièvre, J. M., Latchè, A., Jones, B., Bouzayen, M., & Pech, J. C. (1997). Ethylene and fruit ripening. Physiologia plantarum101(4), 727-739.