Unpacking a Peck of Purple Genetically Engineered Tomatoes

Excitement spread across social media recently with the announcement that a genetically engineered tomato, creatively named “The Purple Tomato” is now available for home gardeners. Gardeners, plant scientists, and others rejoiced at the news that a purple tomato engineered with genes from a snapdragon to boost the plant pigment anthocyanin is now available for home gardeners to purchase. But why were people so excited? And what does this mean?

The Purple Tomato: What is it and why is it exciting and important?

The Purple Tomato was developed by a company called Norfolk Healthy Produce. The company was founded by Professor Cathie Martin (and other scientists) who is a professor at the University of East Anglia and a group leader at the John Innes Centre in the UK. On February 6, 2024 they announced that seeds were available to home gardeners in the US after clearing regulatory approval hurdles by the USDA, EPA, and FDA to assure that it is safe for human consumption, for growth in US without safety containment measures, and that it does meet its claims of added nutrients. Read more about the US regulatory process here.

For all the tomato aficionados out there, The Purple Tomato is an indeterminate cherry tomato. Indeterminate means that the plant doesn’t stop growing as long as it is healthy and will produce a “vine” that needs to be staked or trellised off the ground. Production of fruits continues throughout the season starting at the bottom of the plant and going up as long as it is healthy.  Of course, it is a cherry tomato so you’ll have hundreds or thousands of tiny fruits to pick through the season. Some gardeners love growing cherry tomatoes. Others hate it for that fact. So you win some, you lose some.

Read more on indeterminate vs. determinate here.

The tomato contains two genes from snapdragon flowers that boost anthocyanin production in the tomatoes. Anthocyanins are the plant pigments responsible for blue and blue-purple colors in plants. And they are shared across all plants with these blue and blue-purple colors, so the addition of purple pigments from a flower isn’t too out of the ordinary since tomatoes already contain similar pigments. (The reddish violet/crimson color of plants in the Amaranthaceae family (beets, amaranth, chard) are from betalin pigments, not anthocyanins, FYI.) Most plant pigments actually have the added bonus of also being highly beneficial for human health as most of them are antioxidants and have other health benefits. The incorporation of anthocyanins boost the nutrient quality of tomato since anthocyanins are considered strong antioxidants. Studies also implicate anthocyanins in reducing blood pressure and heart disease, preventing neurological disease, and slowing cancer growth due to the reduction of free radicals that can damage DNA.

Source: Overview of Plant Pigments, Springer

Now, anthocyanins in tomatoes are not new. Many hybrid and heirloom varieties of tomatoes contain anthocyanins. The tomatoes that already contain anthocyanins are the tomatoes that are often considered “purple” or “black” by seed companies and home gardeners. Like ‘Cherokee Purple’, ‘Black Beauty’, and ‘Black Krim’. However, the anthocyanins in these tomatoes are generally found in low quantities as they are only found in the skin and or the flesh just under the skin. What makes “The Purple Tomato” novel is that it is the only tomato that has the anthocyanin pigment in both the skin and throughout the tomato. Seeing pictures of the tomato, the vibrant purple color goes through the entire tomato and is striking. (It also doesn’t hurt that purple is my favorite color). Due to this purple color throughout the tomato, the fruits have a much higher concentration of anthocyanins than existing cultivars.

Another thing that excites me about The Purple Tomato is that the company claims that is an inbred/open pollinated variety. Meaning that home gardeners can save the seeds from year to year and the anthocyanin traits will continue to be present. This also signals a departure from normal genetically engineered seeds where the traits aren’t as persistent and seed saving isn’t allowed. The company does have some terms and conditions about not selling seeds (from the ones you buy or likely from any you save) and not using them to breed other varieties. But gardeners are free to save seeds and share fruits, plants, and seeds with your local community.

“GMOs” and home gardening

Despite what many people may think, until the release of this tomato there really weren’t any genetically engineered plants available to home gardeners. This marks the first time that a plant has received approval from the US government agencies that control the release of genetically engineered plant for sales directly to home gardeners. Most of the genetically engineered plants have been developed for and are available only to commodity crop (corn, soy, cotton, etc.) and select horticultural crop (papaya, some select squashes, and now Arctic apple) farmers. There’s a highly regulated process and contract procedure for farmers to obtain the seeds or plants that just isn’t practical or cost-effective for the plant developers to market to or make seeds for home gardeners.

Source: UC Davis Biotechnology Program

We’ve written several times about how, until now, there really hasn’t been genetically engineered seeds available to home gardeners, despite what some seed companies would have you believe (here and here). There has unfortunately been a lot of confusion for home gardeners thanks to misguided and/or deceptive marketing practices by certain (heirloom) seed companies that labeled their “Non-GMO certified” seeds and preached about the dangers of genetic engineering to sell more of their seeds even though there have not (until now) been any “GMO” seeds available for companies to even sell to home gardeners. Unfortunately that deceptive marketing created enough fear and fervor that most seed companies had to start labeling their seeds “Non-GMO” just to preserve their sales and cut down on harassment from folks on social media trying to “call them out” for selling GMO seeds.

Not until the release of “The Purple Tomato” has there been a home garden seed that could be labeled “GMO” and warrant companies needing to label something as non-GMO. But still it is only one plant, so is it really necessary? Or is it just a marketing tactic?

Purple Tomato Reception

In cruising through the comment section on articles discussing the new tomato, I’ve been pleasantly surprised to see the positive response that it is receiving from the public. There are lots of comments excited about the prospect of a nutrient-dense genetically engineered crop, lots of excitement about buying the seed, and even excitement about the super purple color of the tomato. The few negative comments about GMOs being “bad” have gotten a lot of pushback. I don’t think this would have happened 5 or 10 years ago.

Of course, some of the pushback is a little misguided. Statements like “all plants are GMO” show a similar lack of understanding of what is actually happening, even though it is offered in good faith. Yes, humanity has guided and shaped the genetics of all of the plants we eat over the centuries and many plants have therefore been “genetically modified” by humans. But genetic engineering is a more rigorous and scientific process. This is also one of the reasons why scientists and government agencies prefer the term “genetically engineered” or “bioengineered” to GMO or genetically modified to clear up confusion.

It does seem like the tide has shifted on public acceptance of genetic engineering where until recently many people viewed the technology with skepticism and fear, thanks mainly to misunderstanding and marketing.

Much of the fear and distrust of genetically engineered plants have been around the addition of genes to make crops resistant to certain herbicides, to produce natural immunity to insects, and other traits to increase yields. Many have wrongly assumed or claimed that this has resulted in increased application of herbicides. While application of some herbicides like glyphosate has increased, it has been at the reduction of much more dangerous herbicides. These crops have often been developed and controlled by large chemical companies that, perhaps not totally incorrectly, the general public distrusts. Plus, unintended consequences like herbicide resistant weeds have caused issues.

But the new Purple Tomato goes beyond this and I think is applauded for many reasons. One – it was made solely to boost nutrition. While there have been previous (mostly unsuccessful) efforts to do this in crops (see the story of Golden Rice), this is really the first time it has been aimed at home gardeners. Two – it isn’t one of those “big scary corporations” doing it. It is a company started by academics to promote plant science and health. Three – while the plants are patented, there aren’t strict and secretive agreements against seed saving and sharing. And four – the express purpose of the plant is to increase the healthy qualities of the plant.

In conclusion

It seems like many people are excited about this new genetically engineered tomato on the market. I know that I am. It seems like the public at large is accepting and excited by this new health-boosted tomato and the technology used to make it.

I know I’ve ordered my seeds, and many others have as well. The seeds aren’t cheap, $20 for 10, but the process to make them isn’t cheap either. I’m looking forward to trying them out in my own garden.

Disclaimer: No payment or reward was received for this article promoting the Purple Tomato and I have no affiliation with the company. Norfolk Healthy Produce didn’t even know it was being written. They probably don’t even know who the Garden Professors are and they definitely don’t know who I am. That being said, if they want to reach out with some free seeds or swag, I wouldn’t be mad at them.

¡Escandalo! Seedy mixup results in #Jalapeñogate drama across the US

There’s a scandal simmering all across the United States that brings to mind a switched at birth storyline on a steamy soap opera or telenovela.  This scandal, though, isn’t about babies, its about….peppers!  Jalapeño peppers, to be exact. 

The issue, dubbed #Jalapeñogate online, has many home gardeners scratching their heads as to the identity or the issue with the peppers that they planted. You see, instead of those glossy dark green peppers that many are used to putting in their salsas and other favorite spicy dishes, the plants are producing bright yellow peppers.  Some of them are the same shape as jalapeños and some look more like banana peppers. 

A local gardener allowed me to stop by and let me check out their mysterious peppers.

The phenomenon has gardeners, farmers, and officials in multiple states scratching their heads. It turns out there are no stolen tapes with evidence of the problem. Instead, I was first alerted to the problem when some of the garden Facebook groups in Nebraska were abuzz with posts about the mystery peppers.  I’ve since seen news I’ve seen the issue mentioned in news articles from Oklahoma, Kansas, and California and have seen posts on social media sites such as Reddit and TikTok. I scoured many of these sources (TikTok was surprisingly the most informative) and confirmed it with info from friends in the seed industry.

So what happened?  It turns out that the seed trade is global and multi-tiered and sometimes mix ups occur.  It just so happened that this year there were a lot of them.  One US seed company that supplies a lot of seeds to nurseries and other seed companies, called Seeds by Design, imported some of its seeds for the current season.  The company supplies many interesting and niche seeds, many of which it develops or breeds (they are responsible for the award winning Chef’s Choice tomato series and several other vegetable cultivars that you’d recognize on the seed rack). But it also purchases or imports seeds often for more common varieties.  Seeds by Design supplies seeds to many nurseries, growers, and even seed companies around the country. And that’s where the trouble starts. 

I mentioned #Jalapeñogate on our TV show Backyard Farmer, which fanned the fiery (and not so fiery) pepper flames in Nebraska.

The company imported seeds from an international grower that turned out to be mislabeled.  Up to five different cultivars were accidentally swapped and resulted in pepper pandemonium across the country.  It turns out that more than jalapeños were affected, so we should really change it to just #Peppergate. Here’s what was switched:

What was supposed to be Turned out to be…
Jalapeño (green cultivar) Jalapeño ‘Caloro’ (yellow cultivar)
Jalapeño ‘Tam’ (mild green) Sweet banana pepper
Hungarian Sweet Wax Bell Pepper ‘Diamond’
Bell Pepper ‘Chocolate Beauty’Sweet Pepper ‘Red Cherry’
Bell Pepper ‘Purple Beauty’ Hungarian Hot Wax

Gardeners could have bought these at local garden centers or nurseries as transplants.  I know of at least two local/regional garden centers that sold the affected plants.  I’ve also seen that gardeners who bought seeds from some suppliers (I’ve only seen Ferry-Morse so far) may have received at least switched bell peppers.

Nebraska gardeners (at least 90 of them) were quick to share their #Peppergate story with me.

What does this say about our seed and food supply?

Our food system and our seed system are global.  We live in a global economy and companies buy and trade with each other all the time.  Given the scale of this trade, mistakes can and do happen.  I’ve seen some people try to drag Seeds by Design because they purchased seeds from a foreign company that just happens to be in China. But the company doesn’t deserve that. They had no knowledge of the mix up until the peppers were in the hands of growers and peppers didn’t look right. Can you tell the difference between pepper cultivars by seed?

And others have tried to make an issue about trading with China with some comments that hint at outright racism. While there are some security concerns about trading with countries like China, especially in the tech world, trading simple commodities like Jalapeño seeds is standard practice. I’ve also seen comments that importing ag products from other countries means that we can’t support ourselves. But it turns out that we sell a whole lot more agricultural goods to China than we buy.  US producers sold a record-breaking $200 billion (with a b) worth of agricultural products to China in 2022 while we imported $9.5 billion from them.

Given the need to feed so many people economically, we often import from countries that have better capacity to grow what we need due to climate, land, and labor differences.  We also have to take into account seasonal differences.  Even US based seed production companies and breeders will grow in other countries to take advantage of multiple growing seasons. Given our reliance on horticultural imports, we have a robust inspection system to make sure the foods, plants, and seeds we receive from countries like China are indeed safe. 

To wrap this mystery up –

While there’s not much you can do now that you have these mystery seeds, enjoy the fun of trying something unexpected. If you ended up with a pepper that you don’t like or can’t eat (like the Hot Wax for Purple Bell switch), share with friends or donate to a local food pantry. After all, you can’t tell that the jalapeño isn’t green when it’s turned into a jalapeño popper.

Sources

https://www.fas.usda.gov/data/record-us-fy-2022-agricultural-exports-china

Crop rotation makes the garden go ’round

You might have heard of the concept of crop rotation, or even have had someone tell you that you should be practicing it in your home garden. But does this practice developed for use on large-scale farm fields work for small-scale home gardening or backyard farming?  And if so how do you even do it? Let’s take a quick look at the practice and learn how you might implement it in your own garden, no matter the size, if it is practical to do so. 

The Benefits of Crop Rotation

The benefits of crop rotation touted to home gardens for annual fruit and vegetable plants focus mainly on Integrated Pest Management. Keeping certain crops in one spot in the garden year after year can lead to a build up of plant disease microorganisms and insect pests in that area. These findings are largely based on large-scale production systems, like where whole fields that are hundreds of acres are grown as the same crop and switched from year to year. But there still is some benefit for the small-scale gardener, especially with disease build up from soil-borne diseases or debris left in the garden.

The benefits are less clear for insect pests.  Sure, there might be fewer insects that move from spot-to-spot or bed-to-bed in your home garden, but we must remember that insects can fly and a journey of a few feet from one raised bed to the next might not be much of a barrier.  It is sort of like when people ask us if using grub control in the lawn will control Japanese Beetles in their garden. There will likely be a small reduction in the population, but we remind folks that Japanese Beetles can fly pretty good distances, so control will be minimal. 

Crops in rows and beds can be easy to rotate.

Benefits of crop rotation lay below the soil. Different plants use different ratios of nutrients and some even add nutrients to the soil. Legumes have nitrifying rhizobia bacteria that colonize their roots in a symbiotic relationship and there is a net nitrogen increase in the soil after legumes such as beans, peas, alfalfa, or clover have been grown. That’s why one of the major crops added to crop rotations in the “corn belt” is soybeans (or just “beans” if you’re from around these parts). The soybeans contribute nitrogen to the soil, which helps in the production system because corn is a heavy nitrogen feeder. This is especially true if the roots are left behind or if the legume is incorporated like a cover crop.

Given that crops uptake nutrients in different ratios and that some input nutrients into the soil, by planting the same crop year-after-year in the same spot you can end up with nutrient imbalances, especially in raised beds or small plot areas. Using cover crops and incorporating them into the soil is another facet of crop rotation that can build soil organic matter and address nutrient issues. Fertility can also be adjusted with fertilizer and compost, but using rotation will help with overall management.

Rotating in root crops like carrots, radishes, and turnips can also allow for some good soil aeration, especially in no or low till garden situations. 

There’s also research that shows that different plants exude different compounds, like sugars, etc. that attract and feed different microorganisms and rotations which help increase the diversity of the microbiome in the soil. This will not only improve the soil ecology in your garden, but a healthy microbiome can compete with some disease-causing microorganisms to reduce the likelihood of soil-borne disease. Most of us have been told that eating cultured yogurt increases good microbes in the gut and can reduce the likelihood of some illnesses- its kind of like that, but for plants.

How to rotate crops (especially in small gardens)

While crop rotation might not solve all the world’s problems or your garden insect issues, there are still definite benefits to the practice if you can manage it.  For some people garden space is too limited. How do you rotate crops when all you grow is a few tomatoes in the corner of a flower bed?  Other than putting them somewhere else every year, there isn’t much you can do. 

If you have a large garden and especially if you have one that’s a larger tilled-up spot (don’t get me started on tillage), you should definitely be implementing rotation. While I typically garden in raised beds, that usually makes it easy. Crop rotation usually occurs by plant family, so plant families rotate to a new bed each year (more on plant families in a bit). 

In general, a crop rotation plan should mean that plants from the same family aren’t grown in the same place in the garden for at least four years if possible.  If I plant tomatoes in “Bed A” in my garden this year, then I shouldn’t plant them in “Bed A” again for at least four years if possible.  If you’re not growing in beds, then should rotate by rows or by areas of the garden.

Is this practical for every gardener?  No. So I say do what you can. If you have a small space and only grow a few things and want to rotate crops, you can do so by time rotation – growing different crops each year.  Or adding some container gardening to the mix and rotating crops into containers in different years. As a side note, using containers can be an effective way to rotate crops because you don’t necessarily need to rotate the plants if you can rotate (replace) the soil from year to year (or at least replace the top layers). 

Crop rotation can also aid in succession planting.  For example, I don’t follow my beans with corn, I follow them with garlic, which is also a heavy nitrogen feeder and works right into the garden schedule to be planted in October after the beans are done. I’ll often do lettuce or leafy greens in a bed in early spring, then thin them out to plant in tomatoes or peppers when the time comes. Incorporating intercropping where you plant different sized plants around each other, like my lettuce and tomatoes, can also be an effective addition to crop rotation.

For a good crop rotation, you’ll want to plan.  This would involve sketching/mapping out your garden or at least labeling different beds or spaces. Then creating a chart for each space where you list what crops will be grown there for the next several years will help you plan out to make sure you are giving ample time for the rotation process.

Keeping it in the family

Family members share lots of things and plant families are no different. Not only do some crops look similar but they can often share the same diseases. Keeping families in mind planning crop rotations is one of the easiest methods to keep track of which crops to include in a rotation.  For small gardens it might make sense to keep members of the family together. For example if I only have four beds, I would want all the family members together so that I can have a true four year rotation. In larger gardens, realizing that crops are in the same family will help plan out for rotation of multiple crops. 

Also keep in mind that some crops will overwinter (depending on where you are) so a fall crop might also be a spring crop in the same bed the following year.  Some crops are also biennial depending on your local climate.  For example unless you live in an area with winters cold enough to kill them, swiss chard, onions, and other crops will survive the winter and grow the following spring. I typically leave most perennial vegetables like asparagus and rhubarb, as well as perennial herbs like oregano and chives, out of rotations and put them in their own specific place in the garden (or elsewhere) since they don’t need to be replanted every year.

I’ve put together a list of common annual crops by family, as well as an example crop rotation plan for single garden bed/area. As an example, if I had four raised beds I would use this plan for each bed, starting in a different year for each bed so that I grow all the same crops each year, just in different beds.

Common crops by family. Developed from UF/IFAS Extension
A crop rotation plan I might use in my own garden. If I had four beds, Year 2 crops would be Year 1 crops for bed B and so on.

In conclusion…

Crop rotation isn’t an end-all, be-all garden practice.  If you can institute some sort of rotation in your garden you’ll likely see long-term rewards.  However, if it isn’t possible or seems like too much work just remember don’t plant things in the same place year after year if you can help it.  Any rotation, even if it is hit or miss, will be beneficial. 

Sources

Benincasa, P., Tosti, G., Guiducci, M., Farneselli, M., & Tei, F. (2017). Crop rotation as a system approach for soil fertility management in vegetablesAdvances in research on fertilization management of vegetable crops, 115-148.

Sasse, J., Martinoia, E., & Northen, T. (2018). Feed your friends: do plant exudates shape the root microbiome?Trends in plant science23(1), 25-41.

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 onionNew Zealand Journal of Crop and Horticultural Science45(1), 29-54.

Yasalonis, A. (2019) A must do in gardening: Vegetable crop rotation (UF/IFAS Extension). UF/IFAS Extension (blog)

You gotta know what to sow and what to plant: Veggies and Herbs

As a continuance of my Kenny Roger’s themed article last month on sowing and planting at appropriate soil temperatures, I thought this month I’d approach “Know when to sow ‘em, know when to plant ‘em” in a different way.  When it comes growing vegetables and herbs, many new (and even experienced) gardeners are confused as to which plants you should directly sow into the garden and which ones you must transplant. 

Of course, some of these recommendations might change based on where you are and your local climate.  These are general recommendations based on common practices in most of the U.S. Decisions can be easier to make if you know the reason WHY some things are started indoors and transplanted outside and some things are directly sown, so we’ll start there.

Why transplant?

For the most part, the crops that we start indoors (or purchase at the garden center) and transplant outside are things that either require a long time to reach maturity or require higher temperatures to germinate and thrive than are available outside in regions where these crops are not native. Starting indoors allows us to overcome shorter growing seasons and get those crops to mature in a timely manner.

Many of the warm season crops, such as tomatoes, peppers, and eggplant would likely not make it to maturity if they were directly seeded in the garden after the danger of frost has passed.  And while many cool season crops like the Cole crops (broccoli, cauliflower, cabbage, etc.) thrive when air temperatures are cool, they actually require warmer soil temperatures for germination and would be difficult to direct sow outdoors for a spring planting. In many parts of the country, cool season crops do much better as a fall crop since temperatures get cooler as the crops mature. This means that they should be sown or planted in July or August for most areas. Directly sowing of seed in the garden is technically possible at that time BUT there are many challenges including keeping the seedlings from drying out in the hot, dry summer weather.  So it is usually still easier to transplant, but you can start the transplants in pots in a protected outdoor space rather than indoors if needed. Keep in mind that several of the herbs don’t start well from seed, so you’ll need to buy transplants (which are usually started from cuttings) or take cuttings from an existing plant.

Why direct sow?

There are a number of crops that grow fast or easy enough that they can just be sown directly in the garden. My personal philosophy is that if it can be direct sown you don’t have to worry about the expense or trouble of starting plants indoors or the expense of buying individual plants at the garden center.  Crops like lettuce, beans, peas, corn, squash, and melons are typically very easily sown outdoors. Some folks might opt to start these inside or to buy starts to make it easier, but this is usually at an extra cost that isn’t necessary for success.

Of course, root crops like carrots, radishes, turnips, and beets aren’t easily transplanted because the process of transplanting can damage the root, which is the part you’re trying to grow.  Some herbs like cilantro don’t tolerate root disturbance well, so it is best to direct sow as well.

Knowing when to sow is important as well.  Cool season crops like lettuce, radishes, carrots, and other leafy greens and root crops can be sown well before last frost (see my article from last month, linked above). 

The other thing to keep in mind when direct sowing is that conditions outdoors aren’t as stable as those indoors, so you’ll have to monitor the weather for rapid swings of temperature and also make sure things stay appropriately watered. 

Some crops can go either way

While some crops like squash and cucumbers are easy to direct sow, there might be times when growers might prefer to start indoors (or buy starts) and transplant.  Crops like melons often require high soil temperatures to germinate, so in places where the soil temperature is slow to warm transplanting might be helpful.  Transplanting can also give the grower a leg-up on getting things to maturity quickly. Transplanting is most common for crops where you need a smaller number of plants (like squash and cucumber) but isn’t as practical for crops where you need larger numbers of plants like beans and peas. Keep in mind that crops like cucumbers and squash usually start pretty quickly and will be transplantable after just a few weeks – growing them indoors until they are bigger isn’t necessary and will not create an advantage to getting them to mature quickly.

What to transplant

  • Broccoli
  • Brussels Sprouts
  • Cabbage
  • Cauliflower
  • Celery
  • Collard Greens
  • Eggplant
  • Kale
  • Kohlrabi
  • Lavender
  • Oregano
  • Peppers
  • Rosemary
  • Tarragon
  • Tomatoes
  • Tomatillos

What to Direct Sow

  • Beans
  • Beets
  • Carrots
  • Cilantro/Coriander
  • Dill
  • Leeks
  • Peas
  • Radishes
  • Spinach
  • Sunflowers
  • Turnips

Which Can Go Either Way

  • Basil
  • Bok choi/Pak choi
  • Cantaloupe
  • Chard
  • Cucumber
  • Fennel
  • Lettuce
  • Melons
  • Mint
  • Okra
  • Onions
  • Parsley
  • Pumpkins
  • Watermelon
  • Squash
  • Zucchini

Sources

Master Gardener volunteers transplant tomatoes for the All America Selections trials in Omaha.

Don’t be a garden gambler: You’ve got to know when to sow ’em, know when to plant ’em

For many gardeners around the US (and the northern hemisphere) the weather is warming up for spring planting season and many are itching to get out in the garden. But when is the right time to plant those veggies and flowers and not gamble on their success? Just like Kenny Roger’s character in The Gambler, knowing when to do something is important (this is where I’ll end the cheesy comparison – you’ve just got to come up with a catchy title sometimes).

I’ve spoken previously on this blog about understanding frost dates, which is important for planting warm-season crops like tomatoes, peppers, and cucumbers that won’t survive a frost. (You can read that article here.) But another temperature factor we must consider, especially for cool season plants that we plant BEFORE last frost is the soil temperature.

Soil temperature is especially important for direct sowing seeds in the garden, but it can also affect the success of transplants planted in the garden. For transplants, having an appropriate soil temperature supports root growth and development and helps plants get established faster.

Many warm season plants, especially plants like peppers, won’t establish easily or thrive unless soil temperatures are sufficient for root growth.

Why soil temperature matters for seeds

For direct sowing of seeds, soil temperature has a major effect on the speed of germination, which also affect the success rate of germination. Each different seed has a different optimum temperature for germination. If the soil temperature is below, or above, that level then germination can be slowed down. Slow germination can decrease germination rates through a few different avenues:

  1. Germinating seeds are vulnerable to infection or decomposition by fungi and bacteria in this soil. When starting seeds indoors, this can be limited by using a sterile seed starting mix. But when direct sowing outdoors, there are any number of fungi and bacteria in the soil that will decompose a struggling seed/seedling. Some seeds sold for large-scale production will have a coating of fungicide on them that will provide a few weeks worth of protection. You won’t likely find this on home garden seeds, but it might appear if you buy seeds from a farm supply store or a catalogue that caters to farm-scale producers.
  2. Seeds have a finite amount of stored energy. Once germination begins, the respiration rate of the embryo in the seed radically increases. If germination is slow, the embryo can expend the stored energy before the seed leaves emerge and start producing energy to support the developing seedling. (This also occurs if you plant the seed too deeply).

Below is a graphic I made for Nebraska featuring the best soil temperature range for major vegetable crops (notice how it also lines up with last frost dates). Just ignore the info on frost dates for Nebraska, unless you live in Nebraska.

Most of the resources you’ll find on soil temperature and germination are for vegetable crops. If you are trying to start seeds of ornamentals, you’ll likely have to find the information yourself. The seed packet will give you some indications of when to sow (before/after frost, or maybe in the fall for overwintering to break dormancy) and you can search online for guidance for specific plants. For info on starting seeds indoors, check out this previous article I wrote on the subject.

How to measure soil temperature

Of course, the tried-and-true old fashioned way is to use a thermometer. You can find a soil thermometer at many garden centers and retailers. You’ll want a soil thermometer because the ones for your kitchen likely don’t have the right temperature range – we’re measuring well below the temperature of a roasted chicken here. Instert the thermometer two to three inches into the soil and wait several minutes for the temperature arm to adjust before reading. Also keep in mind that temperatures fluctuate with the weather and throughout the day depending on temperature and the amount of direct sunlight hitting the soil surface – so you want to measure a few times to make sure the temperature is staying within the right range.

Now, the new technological way is to find a soil temperature monitoring station online. Soil temperature monitoring is a common feature of many weather stations these days and data is more available than ever. Many university extension services or ag research centers compile soil temperature maps for use by farmers and this data is also often accessible through NOAAA or weather.gov. In Nebraska, we have an extension program called CropWatch that provides average daily and weekly soil temperatures year round. We also have a weather station with soil temperature probes at our extension office (perks of having a meteorologist as a master gardener volunteer) and we (and our master gardeners) use it when providing information to clients. It can be hard to find a resource that provides soil temperatures nation-wide to share in the patchwork of private and public stations (and the National Weather Service site can be notoriously hard to navigate). There are a few online resources from the ag industry that provide a country-wide system, like this one.

And now its time for me to walk away, time for me to run

Unlike The Gambler you don’t want to wait until after the plantings done to count your money, er, check the temperature. Remember that knowing the soil temperature, whichever method you use, will help your plants succeed in the garden. If you do, your garden could pay out bountiful winnings all through the season.

By knowing the soil temperature, your seeds will turn into a sure bet. Source: Wikimedia Commons

Fair Judgement: garden lessons from a fair (and crop trial) judge

I love a fair! Which is a good thing since I find myself at a lot of them as an extension professional.  It seems like fairs attract extension folks like honey attracts flies.  We’re always involved in the 4-H activities – the livestock, project displays, and contests.  Sometimes we pop up other places as well.  The one thing that I get asked to do multiple times each summer is act as a judge for horticultural entries.  Usually for 4-H youth entries, but sometimes for the open class where anyone can enter their best (or sometimes not so best) produce, flowers, and more.  I thought I’d take a few moments to talk about what I look for as a judge, so if you ever want to enter your best tomatoes or dahlias at the fair you’ll know what to do to get the best ribbon possible.  And even if you aren’t going to enter something into the fair, the rules and guidelines we use can help you select quality seeds and plants for your own garden or help you pick out the best produce at the grocery store or farmers market. 

Produce items and flowers with their ribbons after judging. Each item is judged on its own merits and is not compared to the other entries (except for selection of a “grand champion” or for submission to the state fair).

The fact is, many of the same qualities I look for and skills I use when judging produce and flowers at the county fair are also ones I use as a trial judge for the All-America Selections (AAS) program.  I recently attended the AAS/National Garden Bureau/Home Garden Seed Association summer summit and was discussing fair judging with some folks from seed companies.  They were excited by the process, and especially by the fact that one of the things that I judge (and have gotten fairly strict about) is that the fair entry information contain the cultivar or variety name.  They found this exciting because companies, especially smaller companies, put a lot of work into developing new cultivars, and when the general public identifies specific cultivars as being high quality (as in, I grow XXXX cucumbers because I think they are the best) or at least being able to identify the qualities of specific cultivars then it is sort of like a recognition of the plant breeders and distribution company’s work (and also puts money in their pockets).  As home gardeners, it is important to know which cultivars or varieties work best for you and to be able to identify the qualities you prefer.  It can also be handy to see cultivars out in “the wild” and be able to recall the name of plants you like, which is why the All-America Selections program has display gardens where you can see the edible and ornamental winning plants up close and personal. I’ve written about the trial process for this blog before.

Our display garden on the UNL Campus, which is our home garden for our TV show Backyard Farmer. We feature the garden each week on the show, which is one of the longest running locally produced shows in the US celebrating its 70th anniversary this year. Watch episodes.

Now back to the fairs – this year I used my judgmental eye at five county fairs in the course of three weeks – with three of those fairs in one week.  I’m not sure why I’m so popular, maybe because I’m good at it or maybe because nobody else will do it.  In either case, I do my best to not only judge fairly and by the rules, but also provide valuable feedback as a learning opportunity for youth.  The whole point of fair entries and projects, from our point of view at extension, is not that a kid gets a blue ribbon (in Nebraska the top standard ribbon is purple, though, which I had to adjust to) but that we help raise blue ribbon kids.  In some counties I actually talk to kids, interviewing them on how they grew stuff and giving them feedback on their entries.  When I don’t interview, I fill out a score sheet and provide comments on positives and negatives of each entry. 

Here are a few of the things that I look for when judging, and how they might help home gardeners:

  1. Overall quality, appearance, and health – this is the one that most can identify with.  Does the produce item or flower look appealing and high quality.  Is it free of blemishes, diseases, bug holes, etc.  You’d be amazed at the quality of some things we get at the fair.  Of course, since I usually judge items for kids I do try to provide feedback on how to improve quality overall.  Basically, my reference point is “would I buy this at full price a the market or grocery store”. 
  2. Correct preparation – this is one where lots of folks get tripped up.  For produce items we are often looking for whether or not the item has been harvested correctly, whether or not the stem has been removed or trimmed properly.  It varies by produce item.  These rules seem superfluous and overkill, but they actually are based on guidelines for how to best prepare produce and flowers to extend their shelf life and storability. For example, in Nebraska our guide says to leave a ¼” piece of stem on cucumbers, to remove the blossom cap/stem (sepals) from tomatoes to reduce damage to fruit, to trim beet stems to 2”, to pull (not cut) rhubarb and leave 2” of the leaf blade attached, and so on and so forth.  These guidelines all help reduce damage to produce items or keep them fresher longer – so these guidelines can be handy for home gardeners, too. Herb stems are to be cut a certain length and kept in water (like a bouquet) with the leaves below the water line removed.  For flowers, rules will often state how large of a specimen to provide, and to remove the leaves below the water line.  Rules vary by state and by fair, but many of them are fairly consistent here.  You can find our Nebraska preparation guides for produce and flowers to see how best to harvest and prepare crops and flowers for storage or usage. 
  3. Uniformity of size, shape, color, etc. – this one also trips a lot of people up.  First, most fair rule books will state a specific number of one item that needs to be provided, so that a judge may judge consistency and uniformity across multiple specimens.  For example, our fairs require two specimens of larger produce items (slicing cucumber, zucchini, eggplant, etc), five specimens of medium size items (slicing tomatoes, carrots, potatoes, pickling cucumbers, beets, etc.), and twelve specimens of small items (cherry tomatoes, string beans, etc.).  Flowers usually require five stems, but larger specimens like sunflowers may only require three.  All the specimens provided in the exhibit should be as uniform as possible.  All of the produce items and flower stems should be exactly the same size.  Being the same level of maturity is also important and also leads to uniformity of color, especially in produce items.  Color uniformity is especially important in flowers.  I use this uniformity rule when judging our AAS trials as well – do the plants perform consistently across the whole plant in terms of harvest or flower appearance.  This is a useful skill for home gardeners as well, as you can judge how well a specific cultivar or variety performs for you. You want to grow plants that perform well and provide consistent produce or flowers and not plants that only produce a few good items here and there with questionable produce or flowers mixed in. 
  4. Correct identification and cultivar names – as I stated earlier, the correct identification of the plant (like don’t enter a jalapeno pepper as a bell pepper) and the cultivar or variety are important.  Knowing what the actual end product is supposed to look like is helpful for gardeners to know what they are growing, understand the traits that they want in the plants, and how to select the seeds or plants with the traits they desire.  That’s why the seed company reps got excited about this part – because having gardeners identify specific (newer) cultivars as the ones with the traits they want is important.  It takes garden selection from “I want a slicing tomato” to “I want this specific cultivar of tomato because I know it does X, Y, and Z, so I’ll buy it from this specific seed company that sells it.  That in part is what we do with the All-America Selections trials.  We try out new things (before they hit the market) to test them out for taste, color, disease resistance, and a whole bunch of other things to give a “stamp of approval.”  So any time you see that AAS symbol you know there have been several judgmental eyes (including mine) have assessed those plants and found them worthy. 

So next time you visit a fair take a look at the exhibits to see if you see what a judge looks for.  And think about entering your produce or flowers in a fair near you just to see how your garden skills stack up with your neighbor’s.  Even if you don’t win best of show you can have fun and learn a bit along the way.  And even if you don’t enter at the fair, you can use your judgement to pick the best plants for your garden for years to come. 

Sometimes you get to judge the “fun” stuff, too….like best dressed vegetable.

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.