Author: John Porter

John Porter is a horticulturalist located in Omaha, NE. He is a former extension educator with UNL Extension and county agent with WVU extension. In addition to using his horticulture and extension skills in his home garden, he is a sometimes garden writer and lecturer, a trial judge for All-America Selections, and mentor for local school horticulture and agriculture programs.

Don’t be a Horticultural Hot Mess: Climate-Smart Gardening Practices

While there are still doubters out there mostly thanks to politics, it is pretty clear that the climate is changing and humans are affecting the speed at which it is occurring. The number of record-breaking temperatures and the shift in the USDA hardiness zones show the current effects of this change that will affect almost all parts of our lives, including gardening. What may be less apparent to folks is shifting weather patterns and the increased incidences of extreme weather. Just ask farmers about the weather and they can tell you how extreme weather has gotten. The funny thing is that while many farmers may doubt the existence of anthropogenic (human-caused) climate change, research has show that they believe that weather has gotten worse and that they change their practices and livelihoods to cope with those changes. So as gardeners we can also adjust our practices to deal with the changes as well.

I live in Omaha, Nebraska and we definitely have seen this uptick in extreme weather events this year. From over a dozen tornado touchdowns during the afternoon of Arbor Day (some friends and I got to shelter in place at a warehouse box store for a few hours that day) in a system that had 145 tornadoes across the Midwest. May 2023 was the driest month on record with just 0.17” of rain, feeding the already severe drought in the area. On the other hand, May 2024 was the second wettest May and the eight wettest May on record with 11.14” of rain – the amount that we would normally expect to receive between January 1 and June1 in any given year.

Tornado outbreak of April 26–28, 2024 - Wikipedia
There were 145 tornadoes tracked between April 26 & 28, 2024.

As gardeners we should consider both the long-term implications climate change and the short-term weather extremes that it brings and what sort of mitigation strategies may be needed. And while the individual effect of practices to reduce or sequester greenhouse gas emissions might be minimal, if many people practice climate-smart gardening there could be a small impact – every little bit helps.

Mitigating practices for climate-smart gardening

At this point the change is already happening, so it is wise to think about what practices we need to adopt in the garden to deal with current weather pattern changes and the overall changes of the climate such as increased heat and changing precipitation (some places get less, some places get more). Here are some things to think about:

Plant climate-resilient plants

The advice I often see is that gardeners should “just plant natives,” but it isn’t really as simple as that. Yes, native plants are adapted to the current environment of the area, but will they necessarily be adaptable when that environment changes? The native range for many plants, namely cold intolerant ones, will expand as more areas warm. But some plants can’t take the heat. Changing weather patterns also means that areas may become drier or wetter which could affect what grows successfully in an area. To add to this double whammy, most gardeners are planting in urban areas that have been drastically altered from the local native habitat in terms of soil, temperature, water, and more which may make conditions less favorable for native plants. It isn’t guaranteed that what grows as native today will survive in tomorrow’s climate.

It is best to take a blended approach – incorporating native plants that are likely to do well in evolving climate conditions and adding introduced plants from areas similar to what the climate is changing toward. Also keep in mind that many plants, especially fruit trees, require a certain amount of cold weather, referred to as chill hours. These requirements make it difficult, if not impossible, to grow many cultivars of fruits like apples, pears, plums, and blueberries in southern Florida, Texas, and California. As temperatures rise, the areas that struggle to grow these fruits will expand. It is even difficult to grow crops like tomatoes in some of these areas because extreme heat sterilizes pollen and slows fruit maturation. Resilient gardeners may have to turn to climate resilient (heat tolerant) vegetable cultivars in the future.

Chilling Hours: between 35°F and 45°F, Oct. 1 start
Source: Midwestern Regional Climate Center

different fruit and nut tree species ...

Source: Climate change trends and impacts on California agriculture: a detailed review

Improve Soil Health

Healthy, organic-matter rich soil retains water better and supports plant nutrition. Supporting plant health makes them better able to grow when environmental conditions aren’t exactly perfect. Soil organic matter collects and holds water over long periods, making it available to plants longer term if conditions become dry. It can also aid in drainage if conditions become wetter. Increase organic matter through the application of mulches and composts. In vegetable gardens, cover crops can also be an effective means of adding organic matter and nutrients to the soil.

Water Management

Aside from building soil health to retain water, using mulch to reduce evaporation can also effectively improve water management. Organic mulches also help reduce and moderate soil temperatures, which is important especially during extreme heat periods.

Using effective and efficient irrigation can also help keep plants healthy while reducing water usage. Many perennial plants adapted to current environmental conditions (whether they are native or not) can survive without large amounts of water input during normal periods of precipitation. However, during extreme heat or drought even low-water plants may need supplemental water. Most all plants also need supplemental water for the first few weeks or months after planting until they are established.

Create Microclimates

It is a fairly common practice to create microclimates to protect tender plants in cold weather, such as planting near walls or using protective structures like low tunnels or high tunnels for vegetables and fruits. As temperatures rise gardeners may need to consider creating microclimates to protect plants from heat or extreme conditions like wind. The use of shade cloth or shady areas, trellises, and wind breaks can help protect from extreme temperatures, harsh winds, or excessive sun exposure.

File:烏來生態農場溫室草莓.jpg - Wikimedia Commons
Shade structures to reduce heat. Source: Wikimedia Commons

Planting Adaptations

Aside from changing what is planted, when things are planted might also need to change. Planting times for vegetables, fruits, and annuals will likely shift earlier, especially in areas with extreme heat that would negatively effect plants.

Promote Biodiversity

Planting a variety of plants, both native and introduced, will be helpful if the environment becomes unsuitable for certain species. That way, you haven’t put all of your eggs in one basket. Biodiversity will also support wildlife and insect populations that will also be effected by the changing climate. Having a variety of plants for food and shelter will be paramount for supporting pollinators, songbirds, and other species.

Can you effect climate change from your garden?

Like I said earlier, individual garden practices would likely have little effect on slowing climate change, but if lots of gardeners change practices there could be an effect, even if it is somewhat minimal. Every little bit helps. I left extension back in October to work for a company that supports farmers in conservation and climate-smart practices that add carbon to the soil and therefore reduce greenhouse gas emissions. The effect of an individual farmer would be minimal, but working with hundreds or thousands of farmers and hundreds of thousands of acres of crops can have at least some impact.

So what can you do as a gardener? The thing that most people think about is reduced usage of power equipment that relies on gas or diesel. While electric and battery tools rely on the electric grid that still uses fossil fuels, as the grid continues to add renewable and sustainable energy sources the carbon footprint will continue to shrink.

But one of the best things gardeners can do goes back to soil health. Organic matter build up in the soil sequesters carbon. Therefore practices that add organic matter to the soil can also have an impact on greenhouse gas in the atmosphere. Adding organic matter is a starting point, but you want to make sure it stays there. In annual production systems like in vegetable gardens, tillage promotes the decomposition of organic matter which releases the carbon back into the atmosphere. Minimizing soil disturbance by adopting no-till practices is a key step gardeners can take to reduce their carbon footprint (and positively effect soil health). Eliminating soil disturbance when establishing new perennial beds is also beneficial, but perennial plantings, especially trees, are great at sequestering carbon deep in to the soil for the long-term.

Sources

Hort couture or hubris? The growing trend of genetically engineered novelty plants

A few months ago I wrote about the newly released Purple Tomato, one of the first direct-to-consumer genetically engineered plants made available to the general public. (I’m happy to report that my Purple Tomato seedlings are growing along quite well.) Shortly after I wrote that article, I learned about another new genetically engineered plant being released to home gardeners, this time a bioluminescent petunia. So, of course you know I just had to have some.

The Firefly Petunia was released recently from Light Bio, a company based in Idaho.  The company states that they grew out 50,000 plants for initial sale, but have worked with third-party growers to grow out additional plants from cuttings due to high demand for the plants.

The petunia itself is pretty nondescript. It is a small-flowered, white variety that wouldn’t get a second glance at a garden center. But the company introduced a set of genes from a bioluminescent mushroom called Neonothopanus nambi  that make the faster growing parts of the plants (mainly flowers, but also other growing points) glow. The glowing is caused by a reaction between enzymes and a class of chemicals called, funnily enough, luciferins. And this is bioluminescence – it glows all the time in the dark. It isn’t like a “glow in the dark” where they have to charge up with a light source and only glow for so long.

How a mushroom gets its glow
Neonothopanus nambi daytime look to night time look Source: Science News

Just like the petunia, the fungus is pretty nondescript during the daytime, but glows brightly once darkness descends. I’ve seen glowing fungus once in my life. As a kid I once saw what is called Foxfire, a glowing fungus on some decaying logs. It is pretty cool seeing something glowing so eerily in nature. Now, I have that same glow in my garden.

Back to the plants. The plants are a bit of investment, ringing in at $29 per plant plus shipping, but there are some price breaks at higher quantities if you order several or put together a group order. As a startup, I suppose the company is banking on the novelty of the plant to demand such a high price to cover costs. According to several sources, these white petunias are just the start. They’re working on roses, houseplants and more.

But why glowing petunias?

Before I placed my order, I had to take a step back and think about why. Why a glowing petunia? With the tomato there is at least the case of increased health properties with added anthocyanins. But what is a value of a glowing petunia other than a novelty? Is there a purpose? Or is it just hubris? And why are there genetically engineered plants on the market all of a sudden?

While the petunias don’t have a culinary or health value, the value that they bring is one of acceptance and familiarity. For decades now, well organized and funded campaigns have spread fear of genetic engineering. Seed companies embraced “Non-GMO” as a marketing scare tactic to drive up sales due to a fake boogie man. And even bottled water and salt are labeled as “Non-GMO”. But it seems that the tide of public opinion seems like it might be turning.

Seeing the excitement around both the Purple Tomato and this bioluminescent petunia seems to show a growing interest, or at least a waning of distrust, in genetically engineered plants. And It think that is one of the benefits, or maybe the causes, of seeing genetically engineered plants on the market. Researchers have found that the online conversation about genetically engineered organisms seems to be shifting – from less polarized to increasingly favorable.

While there are sill some hiccups and some ethical and environmental issues, most scientists see genetic engineering as the most important tool in addressing issues such as endemic plant diseases affecting staple crops and developing plants that can withstand warmer and drier conditions as the climate changes. In order for us to be able to fully use these tools, the conversation needs to continue to shift to a more favorable position.

Starting off with tomatoes, petunias, and other flowers is also a choice of ease. Growing plants that don’t have native counterparts where there could be unintentional spread of genes in the wild reduces some of the regulatory hurdles plants face in the United States. And while the purple genes introduced into tomatoes could spread to plants in the food supply, the safety risk is minimal. It would be much harder to get approval for, say, a genetically engineered sunflower or coneflower where there are wild-growing natives into which the glowing genes could inadvertently spread.

Why are genetically engineered plants popping up all of a sudden?

Probably one of the reasons we are seeing so many new genetic engineering projects now is that it is so much easier. With the discovery of CRISPR-Cas9 technology, it is much easier for scientists to transform plants with DNA insertions or extractions. This technology has revolutionized the world of genetics and genetic engineering not only in the plant world, but also in the areas of human health and more.

Before CRISPR, there were a few methods of introducing DNA into organisms. The most common one for plants was probably using a plasmid from the bacterium Agrobacterium tumefasciens. This is the cause of crown gall and it works by inserting its own ring of DNA, called a plasmid, into the DNA of the plant. The plant then produces proteins based on the virulent DNA and also replicates the DNA. One of the common method was bombardment, putting the DNA on tiny microscopic beads, usually gold, and shooting them into the tissue. Tobacco mosaic virus was also used for plant genetic transformations, especially in related plants such as tobacco, tomato, and…..petunia. Most of the work I did in undergrad was with the commonly used with model plant Arabidopsis thaliana (mouse-ear cress).

The transformation, or success, rates for these methods was relatively low compared to CRISPR. Plus, where the DNA ended up was random. There was no control over where the new snippets of DNA ended up, or what genes they would disrupt, or knock-out, in the process. I did quite a bit of research as an undergrad on figuring out just what genes were knocked out in certain transformations and what that changed in their physiology or response to stimuli (our research focus was gravitropism and response to red light).

CRISPR has taken away the guessing game from genetic transformations. Scientists can now target exactly where they want genes to be inserted, or in some cases “knocked out” or interrupted so they are not expressed. For example, Arctic Apples were developed by knocking out the gene in apples that makes polyphenol oxidase, the enzyme that causes them to turn brown after cutting. This has created a technology that has the potential to substantially reduce food waste in crops that have similar reactions as well, such as potato.

So I think the trend of genetically engineered plants for consumers will continue to grow. Evolving from novelty plants to plants that serve a higher purposes, such as nutritional value enhancements, climate change resistance, and more. It will take us a while to get there, but as the technology advances so does, it seems, public opinion. Until then, I’ll just enjoy my glowing petunias and purple tomatoes.

Additional Sources

https://www.scientificamerican.com/article/this-genetically-engineered-petunia-glows-in-the-dark-and-could-be-yours-for-29/

https://www.science.org/content/article/mushrooms-give-plants-green-light-glow

https://www.fastcompany.com/91073850/glow-in-the-dark-petunias-are-just-the-beginning

This bud (removal) is for you: Does early flower removal aid plant establishment in fruiting plants like tomatoes?

In many publications and garden resources you see the suggestion to remove flower buds to improve establishment of new fruit and vegetable plants. This advice is shared for both woody and perennial plants like fruit trees and strawberries and for annuals like tomatoes and peppers. And whenever you see someone stating this as gospel, you see someone else stating that it is false or only anecdotal. So the question is – does research support the advice to remove early plant blossoms to improve vegetative plant growth and establishment? Let’s take a look at some recent, and not so recent, research to see what really happens and understand the process.

The Physiological Process

Prior to my extension career teaching people gardening, I fancied myself a budding (ha ha) plant science researcher. Many of my classes, therefore, were focused on plant physiology and genetics. Not necessarily handy in teaching people the basics of gardening, but pretty damn handy in explaining how plant processes work.

As most upper elementary and middle school students will tell you, plants make their own food in the form of the sugar glucose by using energy from the sun through photosynthesis. That glucose is used in the respiration process to release the energy for the plant to use, transformed into other sugars and compounds for functions around the plant, or turned into starch for long-term storage. Photosynthesis is not an unlimited process and genetics, environment, and other factors play a role in the rate of energy development. So it stands to reason that there are lots of things that have to happen with the finite resources made by the plant.

In plant physiology circles, photosynthesis is called the “source” of plant energy and those uses, such as root, leaf, stem, wood, flower, and fruit production and storage are called “sinks” (sometimes also “pools”). Researchers often discuss these pathways as “source-sink” interactions. Since there are only so many carbohydrates to go around, researchers have long known that when demand is high for growth of certain structures that development of other structures is slowed. If there is a period of rapid root growth, the demand for carbohydrates in the roots increases and the availability for other locations in the plant is decreased. As a result growth in the leaves, stems, or reproductive organs may slow until a supply is restored. But this phenomenon varies by plant species and even cultivar/type, as genetics does play a role in the rate of photosynthesis. Some plants have a higher level of photosynthesis to help offset the sudden upswing of need, and some don’t.

Source: Michael G Ryan, Ram Oren, Richard H Waring, Fruiting and sink competition, Tree Physiology, Volume 38, Issue 9, September 2018, Pages 1261–1266

Think of it like a household budget, but you have a job that only pays you in months that are warm and sunny. You have a set monthly income (the source) and then your housing, utilities, food, and other bills to pay (the sinks). Plus, hopefully you are saving some money for later somehow (another sink). If your bill sinks are greater than your income source, you might dip into your savings a bit, but you don’t want to take it all because you will need most of it in the months when you don’t get paid because it is cold and dreary, or your leaves have fallen off, or your herbaceous bits have died back. As a plant you don’t qualify for credit so the only way to make things work is to cut back in some areas (a sad reality for many on limited incomes). You have to reduce your utility usage, cut back on more expensive foods, find cheaper rent, etc. Similarly, a plant has to reduce the amount of energy used for, say, root growth if it has a rapid leaf growth.

And if you have a kid then the expenses go way up, right? That’s what happens when a plant is just minding its business, enjoying a free and frivolous lifestyle when all of a sudden reproduction comes along. First flower structure development, then fruit development. Plants that have a higher rate of photosynthesis have a higher budget to pull from, so the change may be minimal. But when photosynthesis rates are low, like in newly developing plants with few leaves, unfavorable environments, or genetic limits, the effect can be significant.

So, what about my plant?

The question we always get is, “is it necessary to remove the early blossoms on my ______ plant to help it get established?” For perennials like fruit trees, that would generally be the first few years. For annuals like tomatoes, it would be removing blossoms the first few weeks after planting (and removing any blossoms developed before transplanting).  The answer is…maybe. Or more like, there probably is an effect, but it depends on the plant and environment as to how impactful the effect is. This phenomenon has been observed in several species, including Douglas fir, peaches, olives, and more.

For example, research shows that letting blueberry bushes fruit the first two years after planting (not removing flowers or fruits) reduces the biomass (vegetative growth) AND the yield in year 3. The plants will likely catch up in later years, but if your goal is to get plants established early and have fuller harvests sooner, removing flowers in years 1 and 2 would be advisable.

The same can be said for strawberries. The abstract from this paper from 1953 (I couldn’t track down the full article prior to publication) says that “removal of blossom from newly set strawberry plants helps more in the establishment of a vigorous planting than almost any other cultural operation.” This paper doesn’t measure biomass, but did find that removing flowers on day-neutral strawberries (that produce throughout the growing season) until July 1 resulted in maximized yields in the later season and removal of flowers for the entirety of the first year resulted in maximized yields in year 2 (note: in commercial strawberry production, strawberries are usually grown as an annual or at most a biennial, so maximizing early yields is important).

Now, for the all important tomato (drumroll, please). This study from the 70s found that removal of early blooms on indeterminate tomato plants resulted in larger plants (higher vegetative growth) and that eventually the fruit yield nearly caught up with the controls. They found that when fruit development started, leaf growth was “markedly depressed” and root growth ceased (and there was even some root death). So while there was ultimately a small loss of yield, the result was a better established plant that would likely be able to better weather environmental and disease issues throughout the season.

And beyond establishment, flower and/or fruit thinning on plants with high floral numbers has been shown in many plants (apples, blueberries, peaches, and tomatoes, to name a few) to result in larger, higher quality fruits. The same pathways apply here – each and every fruit is a sink. The more sinks you have, the more “mouths” the plant has to feed. So flower removal is a viable production strategy for many different crops and something that home gardeners should think about if you want the biggest, and juiciest fruits on the block.

Sources:

  • Chanana, Y. R., et al. “Effect of flowers and fruit thinning on maturity, yield and quality in peach (Prunus persica Batsch).” Indian Journal of Horticulture 55.4 (1998): 323-326.
  • Dejong, Theodore M., and Yaffa L. Grossman. “Quantifying sink and source limitations on dry matter partitioning to fruit growth in peach trees.” Physiologia Plantarum 95.3 (1995): 437-443.
  • Eis, S., E. H. Garman, and L. F. Ebell. “Relation between cone production and diameter increment of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies grandis (Dougl.) Lindl.), and western white pine (Pinus monticola Dougl.).” Canadian Journal of Botany 43.12 (1965): 1553-1559.
  • Hesami, Abdolali, Saadat Sarikhani Khorami, and Seyedeh Samaneh Hosseini. “Effect of shoot pruning and flower thinning on quality and quantity of semi-determinate tomato (Lycopersicon esculentum Mill.).” Notulae Scientia Biologicae 4.1 (2012): 108-111.
  • Hurd, R. G., A. P. Gay, and A. C. Mountifield. “The effect of partial flower removal on the relation betwen root, shootand fruti growth in the indeterminate tomato.” Annals of Applied Biology 93.1 (1979): 77-89.
  • Kim, Jin-Gook, et al. “Effects of cluster and flower thinning on yield and fruit quality in highbush’Jersey’blueberry.” Journal of Bio-Environment Control 19.4 (2010): 392-396.
  • Link, H. “Significance of flower and fruit thinning on fruit quality.” Plant growth regulation 31 (2000): 17-26.
  • Michael G Ryan, Ram Oren, Richard H Waring, Fruiting and sink competition, Tree Physiology, Volume 38, Issue 9, September 2018, Pages 1261–1266, https://doi.org/10.1093/treephys/tpy114
  • Rosati, Adolfo, et al. “Fruit production and branching density affect shoot and whole-tree wood to leaf biomass ratio in olive.” Tree Physiology 38.9 (2018): 1278-1285.
  • Scott, D. H., and P. C. Marth. “Effect of blossom removal on growth of newly set strawberry plants.” (1953): 255-6.
  • Solomakhin, Alexey A., and Michael M. Blanke. “Mechanical flower thinning improves the fruit quality of apples.” Journal of the Science of Food and Agriculture 90.5 (2010): 735-741.
  • Williamson, Jeffrey G., and D. Scott NeSmith. “Evaluation of flower bud removal treatments on growth of young blueberry plants.” Hortscience 42.3 (2007): 571-573.

Trials and Triumphs: All-America Selections Judging and 2024 Winners

I’ve written before about my time as a trial judge for the All-America Selections program, which I did during my seven years with Nebraska Extension. I happened upon the opportunity to be a judge by accident, but really came to relish my time and the work that the organization does.

You see, All-America Selections started in 1932 as a way to actually certify the claims that newly-introduced plants were actually better than ones already available. Previously it was sort of the wild-west of claims made by everyone who had a garden catalog or wrote a garden publication. There was no way to level the playing field and certify these claims until W. Ray Hastings, the president of the Southern Seedsman Association, established the All-America Selections trial program. As a non-profit and now part of the National Garden Bureau, the organization and its volunteer judges can serve as impartial arbiters of the superiority of newly-introduced plants.

This emblem on a seed packet or plant label indicates that the plant has gone through rigorous testing and performs well in gardens across the US (and beyond).

This is especially important in this day and age of spurious claims and piles of misinformation on the web. The organization uses a research-based approach in determining high-quality plants with replicated trials all across the country. Plants have to perform well in all regions of the country to be a winner. Sometimes if a plant does well in one area but not others, it will be considered a regional winner.

Ninety-one years later the organization still serves as the gold standard for performance in home garden plants. Judges have a track record of picking plants that are favored even decades after they are introduced. The ‘Celebrity’ tomato, winner from the class of 1984,  has probably been grown by almost everyone who grows tomatoes and can be found in almost every garden catalog or seed rack. ‘Bright Lights’ Swiss Chard, class of 1996, is also a go-to favorite for almost anyone who grows chard. And while many plant cultivars come and go with trends and company closures, there are still seven cultivars from the first class in 1933 still available for home gardeners to purchase through retailers: Tomato ‘Pritchard’, Spinach ‘Giant Nobel’, Pansy ‘ Dwarf Swiss Giants’, Nasturtium ‘Golden Gleam’, Carrot ‘Imperator’, Canterbury Tale ‘Annual Mixed’, and Cantaloupe ‘Honey Rock’. You can check out their profiles on the AAS website to see where to buy them.

2024 Winners

So far there have been 10 winners announced for the 2024 garden season. It unlikely that any more will be introduced at this point, but they often aren’t announced until they are ready to go to market so there’s always a chance. I served as a judge for the edible crops (vegetables, fruits, herbs) for both in-ground and container trials so I’ll start with the edible winners. Then I’ll also share info on the ornamental winners.  You can always find more information, including which seed and plant suppliers/retailers carry the plants, at the AAS website.

Broccoli Purple Magic F1

Broccoli Purple Magic - AAS Vegetable Winner

A striking purple broccoli with tight growth habit. Judges noted it for its great broccoli flavor that was sweeter and more tender than the green broccolis to which it was compared. It was also noted for its heat and stress tolerance.

Broccoli Skytree F1

Broccoli Skytree All-America Selections Winner

This broccoli’s long stalks set it apart. They make the compact heads easy to harvest. It is also noted that the stalks themselves are tender, sweet, and flavorful so they should be eaten as well. It is noted as being uniform and early maturing. Skytree was a regional winner in the West and Northwest. Container suitable.

Pepper Red Impact F1

All America Selections Winner Red Impact Pepper

This is a Lamuyo pepper which is a Spanish pepper noted for exceptional sweetness. It is sweeter than your standard bell pepper. The fruits are huge – nearly 8” long and double the size of standard bell peppers. We noted that they were delicious and sweet, even when green.

Celosia Burning Embers

All America Selections Winner Celoisda Burning Embers

A beautiful and long-lasting celosia in the garden. It is noted for its bronze leaves with pink veins and bright flowers. It is well-branched, heat and drought tolerant, and long-lasting in the garden. It lasted well past other types trialed. Container suitable.

Geranium Big EEZE Pink Batik

All America Selections Winner Geranium Big EZEE Pink

This geranium was noted for its long-lasting flowers and large flower heads. The prolific and large flower heads have a unique pink and white mosaic design. Judges also noted that it was very sun and heat tolerant. Container suitable.

Impatiens Interspecific Solarscape ® Pink Jewel F1

AAS Winner Impatiens-Solarscape XL Pink Jewel

Noted for the bright pink flowers with an opalescent sheen, these flowers lasted well through the season. These plants are sun tolerant and also noted as being resistant to impatient downy mildew, which has basically made it almost impossible to grow (or buy) impatiens lately. Container suitable.

Marigold Siam Gold F1

Marigold Siam Gold - National AAS Winner

This large-flowered marigold was noted for season-long performance. It was also noted that the plants didn’t need staking, even though they were tall and had large flowers making them top-heavy. Container suitable.

Petchoa Enviva™ Pink

All America Selection Winner Petchoa Enviva Pink

You might be asking yourself the same question I did – “what the hell is a petchoa?” And the answer is great – it is a hybrid cross between an Petunia and a Calibrachoa, often called Million bells. The result is a beautiful, mounding plant that is covered with large, beautiful pink iridescent flowers with yellow throats. The judges noted that plants performed well all summer, even in extreme conditions. Container suitable.

Petunia Sure Shot ™ White

The judges noted that this petunia performed like a powerhouse all season long, including extreme summer heat and weather. Most notably, the flowers kept their snow-white flowers all season, whereas many white flowers fade or get blemished quickly after blooming. Regional winner from the West, Northwest, and Great Lakes regions. Container suitable.

Verbena Sweetheart Kisses

Verbena Sweetheart Kisses

This blend of verbena has pinks, roses, reds, and whites that were super attractive to bees and other pollinators. Judges also noted the fine foliage, which isn’t like standard verbena foliage. The plants performed well all season long, even in heat and drought. Container suitable.

Petchoa – bringing together the best of the Petunia and Calibrachoa worlds

Wrapping it up

Finding that AAS seal is a great way to assure that you’re buying high performing plants for your garden. I truly did enjoy my time as a judge, even though my trials were often “if it lives through this, it definitely deserves an award” type of gardening. Now that I’ve left Extension, I’ll no longer serve as an official judge, but I still plan to volunteer to help the Extension office and serve as an “ambassador” for the AAS program. I’m glad they’ll let me stick around!

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.

Shoveling the Artificial CRAP: Navigating Gardening Un-Intelligence in the age of AI

Like it or not, the use of AI (Artificial Intelligence) has become a part of our daily lives. While you might not use AI directly (or you don’t know that you do) it is now a common part of society, especially in the online world. Many people, sites, can companies use it to create content. It is part of the “smart” gadgets that we use at home. Map software (like Google Maps), search engines, ride share apps, and even the spam filter on your email all use AI. You’re even more likely to encounter AI on social media and even standard media these days, with it being used to write articles and text, create ads, and images.

We know that there’s no getting around it these days. You’ve probably heard stories about how AI provides incorrect information, steals content, or might help the robots overthrow humanity today. While it seems to be the wild, wild west, there are a few (voluntary) safeguards in place now to prevent the overthrow of humanity (I hope).  Where the real damage is right now is the use of AI to mislead people outright. There’s also some danger from just lazy use of AI where whoever is using it to create content just copies and pastes it verbatim without checking what it actually says.

Gardening misinformation on the internet is nothing new. Gardening misinformation before the internet is nothing new either. But the risk that AI poses is the amplification and multiplication of that information. It is now easier than ever for someone to create online content at the click of a button. And the way that AI works is it scours the internet for existing information to learn how to respond. This new(ish) generation of AI is generative, meaning that it can actually put together information to form something new. Previously, if you did an internet search you would just get a list of websites to read for information. Now AI can use those sites as source material and write the information in a new way – however you prompt it to do. Search engines like Microsoft’s Bing (the much-loathed replacement for the archaic Internet “Exploder”) now have AI built in as a feature. AI is only as smart as what it can learn on the internet, and we all know that while there is good information on the web it is also full of a lot of manure.

Identifying Artificial Gardening Information

First, how can you tell if it is AI generated?  At first glance you might not be able to tell. It is just like any writing. There are tools you can use to try to figure it out, but you’ll often find that writing from AI doesn’t have personality. It is often very dry. You can tell it to add humor or any other style to its writing, but it often misses the mark. When I asked ChatGPT (one of the common AI platforms) to add humor to something it sounded like I was trying to be cutesy, like an employee at the famous park in the swamps of Orlando run by a mouse and not my usual wit, sarcasm, and cynicism. AI often fails to see context and answers are often very black and white. Which doesn’t work in dynamic systems like gardening and the environment. AI therefore sticks a lot with generalities and doesn’t often provide a lot of specific information unless you ask for it.

As an example, I prompted ChatGPT to write “three sentences about seed starting”. Here’s what it spit out:

1.Starting seeds is a crucial and exciting step in the gardening journey, allowing individuals to cultivate a diverse range of plants from the very beginning. To initiate successful seed germination, it's essential to provide the right conditions, including proper soil moisture, adequate light, and appropriate temperatures tailored to the specific needs of each plant variety. Patience is key when starting seeds, as the process requires careful monitoring and nurturing until the seedlings are strong and ready for transplantation into the garden or larger containers.

Nothing alarming there, but it is pretty dry and isn’t very informative. It isn’t what I would write. Now, I prompted it to rewrite those sentences, but to add “humor and wit”. This is what it vomited out:

Embarking on the seed-starting adventure is like launching a tiny plant spaceship into the garden galaxy – a small step for seeds, a giant leap for your green ambitions! Think of starting seeds as playing matchmaker for your plants, introducing them to the perfect conditions for a successful germination romance – a cozy soil bed, a flirtation with sunlight, and a temperature that says, "I'm hot for you, seedlings!" Growing plants from seeds is a bit like raising the green equivalent of toddlers – they demand attention, throw tantrums if the conditions aren't just right, and you'll find yourself wondering if they've developed personalities before you know it!

Vomit, indeed. Though still nothing too alarming. Definitely too cute and not enough snark.

Where AI generated text falls short is that it incorporates some of that incorrect manure from the web in answers. It doesn’t know that information on the web is incorrect. A few times it told me to put rocks in the bottom of pots for drainage (something we’ve fiercely disproven time and time again).

It told me to practice companion planting (another fallacy we’ve taken on) but it never gave me a lot of details about how to do it.

I did ask it directly about biodynamic gardening, which is the pinnacle of garden misinformation. It gave an amazingly nuanced and diplomatic response, which is much closer to what I’d actually say and much nicer than what GP founder Dr. Linda Chalker-Scott would say. (Don’t tell her I said that).

“Biodynamic gardening is a holistic approach that considers the interconnectedness of plants, animals, and the environment. While some gardeners find it beneficial for promoting sustainability and soil health, its importance depends on individual preferences and beliefs. Biodynamic practices often involve using lunar cycles and special preparations. If you value a holistic and spiritual approach to gardening, incorporating biodynamic principles might align with your preferences. However, it's not essential for every gardener, and many successful gardens thrive with conventional organic practices.”

So, nothing too earth shattering in text, but where I think the real risk lies is in AI generated images and videos. It is easier than ever to create images of things that aren’t possible or incorrect and pass them off as real. People often do this to drive traffic – by making wild claims that people must check out or by “rage baiting” people who just have to respond to tell people how wrong something is (it still drives engagement and earns money). 

Fake images are nothing new in the gardening world. I can’t tell you how many ads I’ve seen for magical rainbow-colored rose seeds, trees that grow 10 kinds of fruits, and more all before the advent of AI. But now it is easier than ever to create those images at the click of a button.

For an example, I turned to DALL-E, which is a common AI Image generator. I tried to think of things that wouldn’t be possible. My first prompt was “monarch butterfly on a snow-covered flower”. Something that isn’t possible, but that someone might create to make a social media post about something amazing or miraculous that people have to see to believe.

The results look realistic(is) enough, though improbable. But you’d have to know that to not believe it.

Image generated using DALL-E with prompt: monarch butterfly on a snow covered flower

The second test, not so much: “realistic looking tree that has 15 different types of fruits and veggies growing on it”. I had to add the “realistic” because the first results were cartoon-y. It didn’t help much. So, I guess my magical 15 fruit and veggie tree won’t be coming to an online scam shop any time soon.

Image generated using DALL-E with prompt: realistic looking tree that has 15 different types of fruits and veggies growing on it

So, I moved on and created “a grape vine covered with scary looking bugs”.

Image generated with DALL-E with prompt: a grape vine covered with scary looking bugs

At first glance, the result can look terrifying. But if you inspect it closely, you’ll see that those bugs have all kinds of legs coming from all over their bodies. Scary, yes, but realistic – no. But could someone do something like this to scare people about an invading insect? Absolutely!

Cutting through the Artificial CRAP

GP Founder Dr. Linda C-S has written about using the CRAP test to identify if a source of information is trustworthy. She used it to talk about Jerry Baker, the self-appointed “America’s Master Gardener” who peddled misinformation and garden snake-oil for decades through books and tv shows to earn big bucks. The same principles can be applied now to digital content created by AI to help figure out if the information is reliable. Here are the steps:

C = credibility. What are the credentials of the person or organization presenting the information? Are they actual experts? Or is it a random account that doesn’t have ties to a credible source? Does the source have academic training, or even practical knowledge?

R = relevant. Is the information relevant for home gardeners? Or does it try to use information other than home gardening, like production agriculture, to answer the questions. For AI, especially images, I could also say that R= realistic. Is it something that could actually be true, or is it a monarch butterfly covered in snow?

A = accuracy. This could lend itself to the realistic assertion, but I see this as more in accuracy of the source of information. Does it site sources, like journal articles, extension publications, USDA reports, etc.? And does the information follow along with trusted information from other sources?

P = purpose. Why is someone presenting this information? In the Jerry Baker example, he was raking in money with books, TV shows, and product promotions. But what benefit does someone get from posting incorrect info on the web? Also, money. Whether you give them a dime, most social media sites and websites generate income by the number of clicks or viewers they have. How do you think people get rich and famous from TikTok? People aren’t paying them to watch them, but they generate income from engagement and interaction. So, creating content that is fanciful to get people to check it out, or even wrong for people to interact with it to rail against it, creates income.

Is all AI bad?

Not necessarily. I mean, the technology is applied in so many ways to solve so many problems. Sure, there is a risk and people do misuse it. But AI can be a powerful and useful tool when used appropriately, when information is checked, and when it isn’t copied and pasted directly. For example. Over most of 2023 I wrote a series of GP articles about plant diseases. No, I didn’t have AI write the article. That would have been wrong. But I did ask my friend ChatGPT to create lists of common diseases for each type of disease to write about. Instead of me having to dig through social media to see what people were asking about, the platform searched to see what the most common diseases that people talked or asked about were, or which ones were most likely to show up on websites. But I took that list, added to it, subtracted from it, and then wrote the article myself. But the more unethical (and lazy) users of AI just copy what it says verbatim without even reading or editing for accuracy. Or even have automated systems that just crank out AI-generated content with no oversight.

In the end, AI isn’t going away. So as savvy gardeners we just have to know what to look for to “spot the bot”.  And always be ready with a shovel to scoop away the CRAP.

Plant Disease Primer Part 5: Malicious Misfits

Over the last several months, I’ve covered plant disease basics and discussed plant diseases caused by fungi, bacteria, and viruses. In this fifth and final installment, I’m going to talk about diseases caused by anything but those three different agents. There are a few diseases caused by pathogens that fall outside of those well-known classifications. This list is by no means exhaustive, but it is a good start to show you just what is out there. Where applicable, I’ll be discussing signs and symptoms of the disease, potential control or prevention efforts, and dive a little deeper into describing the actual causal agent. 

First and foremost, some of the diseases I’m sharing might have already been covered in one of my previous installments. The reason for this is that for simplicity’s sake we often lump diseases caused by these “different” pathogens in with a causal agent that they’re similar or related to or evolved from.  It makes describing these things simpler to the general public. But in this chapter, it is my hope to describe and explore just how these things are different as a lesson in how marvelous, interesting, and varied the world is around us.

Phantom Phytoplasmas

Phytoplasmas are single-celled organisms often lumped in with bacteria, seeing as they are actually descended from bacteria. However, phytoplasmas have lost the cell wall that gives bacteria their shape. Phytoplasmas can therefore change shape in response to their environment and to fit in their surroundings better than bacteria which retain shapes like spherical (cocci), rod (bacilli), and spiral (spirilla).

Since they don’t have the protection of a cell wall, phytoplasmas cannot live outside of a host organism and are considered obligate symbiotes. In the case of a plant parasite, it is either the phloem cells of a plant or the gut of an insect vector. Bacteria, on the other hand, are free-living and can exist in the environment and can move between hosts without the aid of a vector insect.

The best known phytoplasma plant diseases are the yellows, with Aster Yellows being the best known. Yellows diseases get their names because plants or plant parts often turn yellow. They become stunted and can develop mis-formed or misshapen parts. Witches brooming, where many twigs, branches, or flowers develop from one point (which can look like a broom) is common. In aster yellows, misshapen and discolored flowers are common. It affects over 300 species, but coneflower, asters, zinnia, and marigolds are common sufferers. In Ash Yellows, ash trees develop unusual leaf growths and witches’ brooms throughout the tree.

Unusual floral growth as a result of aster yellows Source: Douglas/Sarpy Extension – Nebraska

Phytoplasmas require an insect vector, and in the case of yellows, like Aster Yellows, the culprit is a tiny leaf hopper. For Ash Yellows, spittlebugs may also be carriers in addition to leaf hoppers. Since there isn’t a treatment, infection by yellows phytoplasmas can be permanently effective or fatal. The stunting and yellowing will eventually cause a decline in tree health. For herbaceous perennials suffering from Aster Yellows there is no way to revert back to normal blooms. The only way to reduce the likelihood of spread to other plants is removal of whole plants and it can often be too-little-too-late as leafhoppers spread quickly from plant to plant and infection in other plants often occurs prior to noticeable symptoms in nearby origin plants.

Ash tree exhibiting overall decline and witches brooming from Ash Yellows. Source: Missouri Botanical Garden

Vicious Viroids

In part 4 of this series, we discussed plant viruses and how devastating they are to plants. Viroids are also very destructive disease-causing agents and, like viruses, cannot be cured. Viroids are non-living agents, just like viruses, and are even simpler. Where viruses are genetic material (DNA or RNA) surrounded by a protein coat, viroids are just simple strands of pathogenic RNA without a coat. These circular, single-stranded RNA molecules do not encode any proteins and rely on the host cells for replication.

Viroid symptoms include stunting, misshapen growth, leaf abnormalities, and reduced yield. It is possible for some plants to be asymptomatic while being infected and providing a source of viroids to infect other nearby plants.

Viroids can spread to plants in similar ways to viruses, through transmission on dirty tools, propagation from infected plant materials, on seeds, through touch. There is some evidence that viroids can spread through insect vectors like aphids, which is not common for viral diseases. Prevention relies on good sanitation like cleaning tools, planting disease-free and certified cuttings and seeds, and quarantine of new plants that could be infected.

Common viroid diseases include:

Potato Spindle Tuber Disease (PSTVd)

Common Symptoms: stunted growth, deformed potato tubers, yield reduction

Deformed potato tubers with PSTVd. Source: Wikimedia Commons

Chrysanthemum Stunt Viroid (CSVd)

Common Symptoms: stunting, spotted leaves, poor rooting, flower color change, disruption of photoperiod response for flower initiation. It is one of the biggest threats to the chrysanthemum production industry.

Effects of CSVd on florist chrysanthemum. Source: invasive.org

Oafish Oomycetes

While many still lump oomycetes in with fungi, many scientists consider them to be a distinct group because they have a number of differences. One common name for this group is “water mold” because of their preference for wet environments and their mold-like appearance. While they do absorb nutrients and produce mycelia like fungi, there are differences in their composition, genetics, and reproduction. The biggest difference is the production of oospores, which are thick-walled reproductive spores that can rest, or hibernate, for extended periods of time in unfavorable conditions and “germinate” when conditions are favorable for the organism to grow and reproduce. Another difference is the composition of its cell walls. Fungi cell walls are composed of chitin, which is the same chemical that gives hardness to the exoskeleton of insects. Oomycete cell walls are composed of cellulose and beta glucans (polysaccharides that make soluble fibers).

While late blight of potatoes Phytophthora infestans is often called a fungus (and I discussed it in the fungus installment), it is technically an oomycete. The same with downy mildews of various species (Plasmopara) and blights caused by Pythium spp.. One of the more devastating oomycete diseases is Sudden Oak Death Phytophthora ramorum, which as it sounds, is responsible for the sudden death of plants. But many are now calling it Ramorum blight because it effects way more plants than just oak (Rhododendron, Viburnum, Camellia, Azalea, blueberries, Douglas fir, lilacs, and mountain laurel to name a few). Early symptoms of Sudden Oak Death include foliage dieback, leaf discoloration and water-soaked lesions, shoot and twig dieback. As the disease progresses, trees develop cankers that ooze or bleed dark colored sap and eventually decline and die. There is no treatment or cure for sudden oak death and prevention relies on good sanitation and abiding by quarantine regulations.

Oozing oak canker from Ramorum Blight/Sudden Oak Death. Source: Ohio State University Extension
Water soaked lesion on Rhododendron caused by Ramorum Blight. Source: UMD Extension

Wrapping it up

Just like diseases caused by the familiar fungi, bacteria, and viruses, these plant diseases can be devastating and difficult to prevent or manage. As always, an ounce of prevention is worth a pound of cure (which is really true when there isn’t a cure). The best way to deal with these diseases, as with any disease, it to practice integrated pest management with good sanitation, procuring plants from trusted sources, and being vigilant for signs of disease so that infected plants can be removed quickly to reduce the chance of spread.

Knowing some of the common diseases and their signs and symptoms is key in early detection and decision making. Hopefully, some of the info I’ve shared in this series can help you keep an eye out for diseases. As always, when in doubt contact your local extension office for help with diagnosis, verification, and to discuss possible treatment or prevention options.

Sources

Plant Disease Primer- Part 4: Going Viral

Previously in this series I started with some plant disease basics and then covered some common fungal diseases and then bacterial diseases. Now let’s turn our attention to viruses. Just like with fungi and bacteria before, in this installment I’m going to talk about some of the most common viral plant diseases with some suggestions for treatment and prevention. This by no means will be an exhaustive list of diseases (there are so many!), but I hope to cover some of the most common ones that trouble gardeners.

Unlike fungi and bacteria and just like human viruses like the common cold, there typically aren’t treatments that you can use to “cure” or treat a viral infection. Therefore prevention is the only way to limit viral disease spread in plants. Also unlike fungi and bacteria, viruses are not living organisms.  They don’t have cellular “machinery” and are typically a snippet of genetic material (DNA or RNA) encased in a protein coat or similar structure. Since they aren’t living, they don’t reproduce outside of a host organism and don’t typically have the ability to spread themselves around the environment, instead relying on hosts to carry them. For plant viral diseases this usually involves manual movement on humans, tools, or possibly animals or inside of a secondary host organism like an insect’s digestive tract. Aphids are a common vector, as they consume and secrete infected sap. Viruses can often spread through infected seed or vegetative propagules like seed potatoes or cuttings. And since they aren’t living entities and are microscopic there are no signs (visible presence of causal agent) of disease, only symptoms.

Mosaic Viruses

I’m lumping mosaic viruses together because there are lots and lots of them, each affecting a different range of host plants but with similar symptoms. Many viruses affect a specific species or genus of plants while others have a broad host range. Common symptoms include: yellowing, mottling, mosaic patterns on leaves, curling, stunted growth, reduced fruit quality and size, and necrosis.

Tobacco mosaic virus (TMV) is the most persistent and infectious virus and has a very wide host range, including tobacco and other members of the Solanaceae family like tomatoes, potatoes, and peppers, other vegetables, and ornamental plants. The host range is estimated to be up to 350 species.

Tobacco Mosaic Virus (TMV) on Tobacco, Source: UK Extension

TMV is spread through sap and infected seeds. Virus transmission through sap can be a result of physical contact (brushing against plants when moving through a field/garden), dirty tools, aphid feeding, or even from tobacco use. TMV is so pervasive and persistent that many nursery and greenhouse businesses have strict tobacco policies for employees and for employees who do use tobacco there is usually a hand sanitation requirement.

Tomato Mosaic Virus (ToMV) on Tomato, Source: UF IFAS

Other mosaic viruses include Tomato Mosaic Virus (ToMV), Cucumber Mosaic Virus (CMV), Zucchini Yellow Mosaic Virus (ZYMV), Cauliflower Mosaic Virus (CaMV), Squash Mosaic Virus (SqMV), Bean Common Mosaic Virus (BCMV), and Rose Mosaic Virus (RMV).

Zucchini Yellow Mosaic Virus (ZYMV), Source: Wikimedia Commons

Tomato Yellow Leaf Curl Virus (TYLCV)

  • Common symptoms: Yellowing and curling of leaves, stunted growth
  • Host Plants: Tomatoes, Peppers
  • Insect Vectors: Whitefly
Source: LSU AgCenter

Tomato Ringspot Virus (ToRSV)

  • Common symptoms: yellow rings on leaves, mottling, distortion, mosaic, rings on fruits, necrosis
  • Host Plants: Tomatoes, other Solanaceous crops, wide range of others
  • Vector: Nematodes
Source: Wisconsin Pest Bulletin

Potato Virus Y (PVY)

  • Common symptoms: Leaf discoloration, mosaic patterns, tuber deformation
  • Host Plants: Potatoes, Tomatoes, Peppers
  • Insect vector: aphids
Source: University of Maine

Hosta Virus X (HVX)

  • Common Symptoms: irregular yellow or light green streaks, mottling, leaf distortion, feathering pattern (looks like colors painted on by brush), stunting, and reduced vigor
  • Host Plants: Hosta
  • Insect Vectors: None/unknown
Source: Wisconsin Horticulture

Rose Rosette Disease (RRD)

  • Common symptoms: Rapid growth, witches brooming, excessive red coloration (in terminal bracts), deformed leaves, excessive thorns
  • Host Plants: Roses
  • Insect Vectors: Eriophyid mites
Source: NC Extension

Plum Pox Virus (PPV)

  • Symptoms: Leaf distortion, fruit deformities
  • Host Plants: Plum, peach, apricot
  • Insect Vectors: Aphids
Source: USDA APHIS

Control and Prevention

Unfortunately, since there is no treatment for viruses and plants don’t have immune responses that eliminate them like humans and animals do, the only “control” for viruses in the garden is by removal of infected plants. There is no way to “cure” an infected plant, but removal from the landscape or garden can reduce the viral load available to vectors in the garden and can help slow or eliminate the spread to other plants. Since symptoms may not appear right away, it is possible that viruses can spread to multiple plants before detection. 

Since viral infection typically means a death-sentence for the plant, prevention through Integrated Pest Management is of utmost importance.  Here are some common and effective IMP practices that can help reduce the spread of viruses in the garden.

  1. Purchase certified disease-free seeds or plant cuttings. Unfortunately, viruses can spread easily through untested seeds and cuttings so take caution in sharing at places like plant and seed swaps.
  2. Practice good sanitation: remove and destroy infected leaves and plants ASAP
  3. Clean tools regularly: viruses spread through sap transfer, so cleaning and disinfecting tools is a must. Sometimes in high-value or susceptible plants, disinfection should be done between using tools on individual plants, especially pruners. Use a dilute 10% bleach solution, rubbing alcohol, or horticultural sanitizer for best results.
  4. Quarantine new plants: If a plant appears suspicious, keep it potted in an out of the way place until you can determine possible infection. This is especially important for plants from discount retailers, plant swaps, etc but can hold true for plants from any source.
  5. Purchase disease-resistant cultivars when possible.
  6. Control vector insects, especially aphids.
  7. Wash hands before gardening, ESPECIALLY if you are a tobacco user.
  8. Do not use tobacco products while gardening.

Wrapping it up

There are lots of bacterial diseases that can damage or kill plants in our gardens or landscapes. Prevention is key, as treatments only help slow the spread of disease. In the next (and final) installment, we’ll talk about diseases that are caused by things that aren’t fungi, bacteria, or viruses.

Plant Disease Primer -Part 3: Fight Bac(teria)

Previously in this series I started with some plant disease basics and then covered some common fungal plant diseases. Now let’s turn our attention to bacteria.  Just like with fungi before, this installment of the series, I’m going to talk about some of the most common bacterial plant diseases with some suggestions for treatment and prevention. This by no means will be an exhaustive list of diseases (there are so many!), but I hope to cover some of the most common ones that trouble gardeners. Most diseases have similar control and treatment options which will be shared in a section at the end, but special cases are noted in the list of diseases.

Fireblight (Erwinia amylovora)

  • Signs & Symptoms: Wilting and blackened young shoots with “shepherds crook” bend, brown/burnt blossoms
  • Host plants: Apple, pear, quince, and relatives
  • Treatment notes for Fire Blight: The bacteria is spread through pollen during bloom. Most common treatment is pruning out affected branches. Some application of the antibiotic streptomycin may help, but it must be applied to flowers and care must be taken to avoid potential side effects for pollinators. Use of copper fungicides in the dormant season may limit spread.
Classic fire blight looks like the ends of branches have been burned

Bacterial Leaf Spot (Xanthomonas spp.)

  • Signs & Symptoms: Small, water-soaked lesions on leaves; dark lesions with yellow halos, premature leaf drop and reduced plant vigor
  • Host plants: Various, including tomato, pepper, and crucifers

Bacterial wilts (Ralstonia solacearum, solanaceous crops; Erwinia tracheiphila; cucurbits; others)

  • Signs & Symptoms: wilting of leaves, usually rapidly and whole branches at a time; yellowing and browning of leaves; vascular tissue discoloration; rapid death
  • Host plants: solanaceous crops, cucurbits, many others

Crown Gall (Agrobacterium tumefaciens)

  • Signs & Symptoms: tumor-like growths/galls on stems, roots, and crowns; stunted growth and reduced yield
  • Host plants: many
  • Fun fact: A. tumefaciens transmits a small bit of DNA to the host plant, a circular plasmid, that causes the tumor-like growth. This was used as one of the first methods (and is still used) to genetically engineer plants by introducing new DNA.

Bacterial Soft Rot (Pectobacterium and Dickeya spp., others)

  • Signs & Symptoms: water-soaked, mushy, and foul-smelling lesions on plant parts, especially fruits and tubers (the classic “rotten potato” smell); rapid decay, slimy
  • Host Plants: potatoes, others

Angular Leaf Spot (Pseudomonas syringae)

  • Signs & Symptoms: angular, water-soaked lesions on leaves; lesions are often limited by leaf veins; premature leaf drop and reduced vigor
  • Host Plants: cucurbits, most commonly cucumber
The flow of bacterial cellular streaming is impeded, or limited, by leaf veins, resulting in “angular” spots

Bacterial Canker (multiple)

  • Signs & Symptoms: Canker-like lesions on stems and other plant parts; lesions may or may not ooze bacterial exudate; for citrus canker, lesions are common on fruits as well
  • Host Plants: many, usually pathogen specific

Bacterial Ring Rot (Clavibacter michiganensis)

  • Signs & Symptoms: brown ring/rot inside tubers; foliage yellowing and death
  • Host Plants: Potato, sometimes tomato

Treating Bacterial Diseases

Just like I discussed with fungi last month, it is difficult to eliminate bacterial diseases once present. Treatment focus should be on slowing down the spread of the disease to the remaining plant. Treatment is important for annual plants, which may be killed entirely by pathogens, and in woody perennials where symptoms include cankers or rots that affect perennial plant parts such as stems or trunks. Bacterial diseases that affect only foliage on perennial plants are less of a threat and often the damage is limited to aesthetics.

For the most part, removal of the diseased plant parts is an important first step in treating the disease. Bacteria stream, or ooze, through plant parts (this is why signs and symptoms are sometimes limited by plant structures, like angular leaf spot lesions being stopped by leaf veins). Therefore the organism may be present a distance away from the visible sign or symptom. For cankers and other stem infections, removal should include “healthy” tissue below (between the callus and main plant).

Sometimes this may require removal of large parts of plants, at which point decisions should be made about removal of the entire plant. Cankers occurring on main stems or trunks are especially devastating.

Once affected plant parts are removed, a treatment with a copper-based product may reduce spread. While often used as a fungicide, copper does have some effect on bacteria. Except for in the case of fire blight (usually in commercial orchards), treatment with an antibiotic is not practical or possible. Often repeated treatments through the season are needed once the disease is established in the nearby environment. Care should be taken to not overuse copper sulfate, as it will not break down in the environment and can build up in the soil, causing damage to populations to good fungi and bacteria in the soil. 

Bacterial Prevention through IPM

Just as in fungal diseases, there are several Integrated Pest Management strategies that can be used to reduce the likelihood of bacterial infection in your garden or landscape. Below are some strategies that can be used for general fungal prevention:

  • Use mulch to limit splashing of soil onto plants
  • Eliminate overhead watering to reduce foliar moisture
  • If overhead watering is necessary, water early in the day so plants dry out before the dew point drops in the evening
  • When possible, plant disease resistant cultivars
  • Reduce nearby weeds to eliminate potential secondary hosts
  • Practice good hygiene in the garden by cleaning up any fallen or diseased leaves, fruits, etc.

Wrapping it up

There are lots of bacterial diseases that can damage or kill plants in our gardens or landscapes. Prevention is key, as treatments only help slow the spread of disease. In the next installment, we’ll talk about viruses and virus-like pathogens. Stay tuned!

Plant Disease Primer-Part 2: Fungus Among Us

In my last post, I talked about the factors leading to the development of plant diseases and some common signs and symptoms of fungal, bacterial, and viral diseases. In this installment of the series, I’m going to talk about some of the most common fungal plant diseases with some suggestions for treatment and prevention. This by no means will be an exhaustive list of diseases (there are so many!), but I hope to cover some of the most common ones that we see come into the extension office for diagnosis.

Common Fungal Diseases

  • Powdery Mildew
    • Symptoms: White powdery spots on leaves and stems
    • Common hosts: a wide range of plants, but peonies, lilacs, squashes, cucumbers, and roses are what we see most often
Powdery Mildew on Peony
  • Downy Mildew
    • Symptoms: yellowish or whitish spots on the tops of leaves with gray-ish fuzzy growth underneath
    • Common hosts: downy mildew affects many plants, but basil, impatiens, cucurbits, and verbena constitute the most common questions.
  • Rusts
    • Most rust lifecycles require two host plants: a primary and alternate host
    • Common rusts:
      • Cedar-apple rust (Junipers– primary, Apple/pear – alternate)
      • White pine blister rust (white pine – primary, gooseberry/currant – alternate)
      • Hollyhock rust (no alternate host)
    • Symptoms: rust colored (orange/yellow/red) pustules or blotches on leaves, stems, and fruit; may appear as gummy structures on primary host
  • Leaf Blights
    • The most common blights we see are often for tomatoes and their relatives. There are many leaf spots and blights that affect these plants, but early blight seems to be one of the most common.
    • Common leaf blights
      • Early Blight of tomato: irregularly shaped lesions on leaves, often with concentric rings and yellow halos. Eventual leaf curling, necrosis, or dropping. Severe cases can end up with lesions on stems and fruits.
      • Late Blight of Tomato and Potato: Starting as small water-soaked lesions and turning into large, purple-brown, oily looking blotches. Blotches appear on leaves, stems, and eventually fruit.
Early blight of tomato, Source: UMN Extension
  • Anthracnose (multiple species and target species)
    • Anthracnose affects a wide range of plants, but we often see shade trees such as oak and sycamore, dogwoods, beans, peppers, and cucurbits as commonly affected plants.
    • Symptoms: dark, sunken ulcer-like lesions on leaves, stems, fruits, and flowers.
Anthracnose on watermelon, Source: UMN Extension
  • Cankers
    • Common cankers:
      • Cytospera – spruce, pine, poplar, willow
      • Phomopsis – juniper, Russian olive, Douglas-fir, arborvitae
      • Nectria – honey locust, oak, maple
    • Symptoms: sunken necrotic lesions (cankers) on twigs, stems, and trunks of trees. Often leading to death of the plant beyond the canker location. This is especially problematic for trunk cankers which often lead to the death of the whole plant.
Nectria canker on young maple trunk Source: Missouri Botanic Garden
  • Root Rots
    • Common rots:
      • Phytopthora – affects many species to cause root rot
      • Armaillaria – especially problematic for trees
Armillaria root rot (fruiting bodies), Source: UC ANR
  • Fruit rots
    • Common rots:
      • Black rot – many species, but often apple and pear
      • Brown rot – peaches, plums, cherries, and related species
Brown rot on peach, Source: Rutgers

Fungus Treatment

Once a plant is infected with a fungus, it is difficult to eliminate the disease and treatment focus should be on slowing down the spread of the disease to the remaining plant. Treatment is important for annual plants, which may be killed entirely by fungal pathogens, and in woody perennials where symptoms include cankers or rots that affect perennial plant parts such as stems or trunks. Fungal diseases that affect only foliage on perennial plants are less of a threat and often the damage is limited to aesthetics.

For the most part, removal of the diseased plant parts is an important first step in treating the disease. This removes a great deal of the fungal organism from the plant that is likely still producing spores or hyphae to spread through the plant. Removal of affected foliage for foliar diseases is key.

In cankers, removal of whole branches or twigs starting at least a few inches below the canker location is necessary. Sometimes this may require removal of large parts of plants, at which point decisions should be made about removal of the entire plant. Cankers occurring on main stems or trunks are especially devastating.

Once affected plant parts are removed, a treatment with fungicides may be necessary to reduce spread of the disease further. Often repeated treatments through the season are needed once the disease is established in the nearby environment. Copper sulfate is a common organic option for treatment of fungal pathogens, but may not be effective for every disease. Care should be taken to not overuse copper sulfate, as it will not break down in the environment and can build up in the soil, causing damage to populations to good fungi and bacteria in the soil.  Chlorothalonil is a widely used conventional fungicide and will help control many, but not all, fungal diseases.  For specific fungicide recommendations for your area, contact your local extension expert.

Fungus Prevention through IPM

There are several Integrated Pest Management strategies that can be used to reduce the likelihood of fungal infection in your garden or landscape. Below are some strategies that can be used for general fungal prevention:

  • Use correct plant spacing and pruning to ensure airflow around plants. This can reduce humidity within the plant structure and moving air can reduce the number of fungal spores that land on the plant.
  • Use mulch to limit splashing of soil onto plants
  • Eliminate overhead watering to reduce foliar moisture
  • If overhead watering is necessary, water early in the day so plants dry out before the dew point drops in the evening
  • When possible, plant disease resistant cultivars
  • Reduce nearby weeds to eliminate potential secondary hosts
  • Remove rust alternate hosts (not always possible), such as junipers if you’re growing apples (or vice versa)
  • Utilize biofungicides as a preventative measure. Products containing different types of Bacillus bacteria can be competitive with disease-causing organisms and limit their ability to form on leaves.
  • Practice good hygiene in the garden by cleaning up any fallen or diseased leaves, fruits, etc.

Wrapping it up

There are lots of fungal diseases that can damage or kill plants in our gardens or landscapes. Prevention is key, as treatments only help slow the spread of disease. In the next installment, we’ll talk about bacterial diseases. Stay tuned!