April teased us with such a warm start, many farmers and gardeners hustled to get seeds started and in the ground. Alas, May’s cool, wet weather delayed or drenched many of our early plantings! Let’s talk about how to identify and address some of the ways wet spring weather may make crops sad and how we can help cheer them up.

Prolonged wet, humid, cool, and gloomy spells can cause a range of plant problems and stress. Plants rely on the sun to drive their photosynthesizing engine. Solar energy powers leaves to pull up nutrients from root systems, grow healthy foliage, and set flowers and fruit. Long periods without sun can stress plants by causing stems to elongate and grow spindly, lesson nutrient uptake and wash out foliage color, or even pause growth completely.

Additionally, when it’s humid and overcast, more moisture is present in the air. Leaves might stay wet for days, and excess water builds up in or on top of the soil, water logging roots. This weakens plant growth and vitality and may lead to more plant disease.

So what wet weather plant problems are solvable? And which are less manageable and might make it worthwhile to restart some plants in your garden or farm—and yes, it’s still early in the summer so there is plenty of time to catch up or replant many annuals and still have a bountiful garden harvest!

Damping Off: A Seedling Killer

Damping off is one of the most common issues of seedlings in gloomy weather periods, both in transplant trays or out in the garden. “Damping Off” is not a single disease, but rather a complex of diseases that can occur singly or together, but that have similar impacts on the plants (kind of like how you can be sick, and it’s not always clear if you have a cold or a flu). Damping off may cause seeds to rot, stunt transplanted seedlings, but in its most common form it happens just above the soil and makes it look as if somebody came along and pinched your stem and caused the top of the plant to keel over.

Damping off most frequently occurs when seedlings are in an excessively moist environment without much sun or airflow (just like what is created on these cloudy overcast days). Most of these causal pathogens can spread between plants on soil, tools or hands, or infested plants. It can also spread via insects like fungus gnats. It is most common to see in indoor seed starting situations, but in extremely wet years it is also possible outdoors in your actual garden.

Damping off is not curable for affected plants. However, it may be possible to save other plants near the infected area by getting more airflow on them, reducing your watering frequency, and increasing their light access. If garden plants are affected, the same rules hold. If you can, remove the infected plants to give more space for air to flow around the survivors. Reduce your watering on gloomy days and keep an eye on if the infection is spreading.

Classic damping off presentation in watermelon seedlings, with that pinched off lesion near the soil surface. Image from Purdue’s Vegetable Crops Hotline, by Dan Egel, https://vegcropshotline.org/article/damping-off-of-vegetables/

Planting Delays and Overgrown Starts

Years with wet springs might also delay field work and planting and lead to overgrown transplants. If you are trying to hold vegetable or annual transplants in cells until the soil can dry out enough to work, there are a few tips that might buy some time:

• Valuable crops might be worth potting up to larger container sizes so you can keep them indoors and drier for a week or two longer.
• Cooler temperatures for transplants (which nature has been doing in conjunction with the rain so far) can also slow down transplant growth and lengthen the time you can leave them in their cells. Lower temperatures that slow growth may also help reduce the legginess that develops in the low light conditions we’ve been seeing.
• Reducing watering can start to harden the plants off and slow down growth. (Don’t reduce water to the point that it stresses the plants, however, and it’s better to water deeply less often than shallowly every day.)
• If you have the space and time, it might be worth considering changing some of the delayed plantings from direct seeding to transplants. Some crops that are typically direct seeded can alternately be transplanted (eg beets, spinach, corn, most greens, cucumbers, zucchini, squash, and even beans and peas). Some of these as transplants have a quick turnaround time (2-3 weeks in cells) and sensitive roots but can still be transplanted as an option to buy some time.

Choosing what to save and what to start over can be stressful. However, it’s also frustrating to spend months growing something and not get a harvest because it was so stressed or overgrown at the seedling state of its life. Make sure to assess your seedlings and be honest about their vigor. It might be worth saving that beautiful tomato plant from your home-saved seed but might not be worth salvaging that flat of sad lettuce.

Slugs and Snails on the Slither

Snails and especially slugs unfortunately *love* this weather. We are seeing heavy feeding starting early this year! These pests hide during the day in protected areas and can travel up to 40 feet to feed at night. Field edges or near drive aisles, gardens with heavy crop residue, or hedgerows and brushy areas are all high traffic zones for slugs. They can be highly active near the edges of greenhouses and buildings, or where any structure or object meets the ground. You will get the best sense of the situation if you go out at night with a flashlight (brace yourself!).

Cultural management practices over the long term are the most effective control (but unfortunately not immediately helpful). These include reducing habitat areas for the slugs by mowing borders or garden edges, avoiding planting in high slug zones near wet areas, tilling a strip between your crops and the field edge and keeping that strip clean, and practicing good weed control and field sanitation.

In the shorter term, try to increase airflow around the plants—this includes pruning and thinning plants, keeping weeds down, and staking or trellising plants. The goal is to remove hiding places for the slugs. Clean, bare ground is less attractive to a slug than a heavily mulched garden, and mowing grass low around your garden may keep habitat down.

You can also mount a physical attack on the slugs, either picking them off plants yourself, or setting up traps. Effective traps include board traps, pitfall traps (shallow containers level with the soil surface filled with yeasty water or beer), and encouraging predators like snakes, toads. There are some chemical controls labeled for slugs and snails, but please read the label and follow all directions. (For commercial growers, there are a number of products listed on NYSPAD: https://extapps.dec.ny.gov/nyspad/?0 )

However, in a heavy slug year (and boy are we in one), even doing all the possible slug controls may not have perfect efficacy!

When harvesting with heavy slug activity, doing it when it’s sunny (or as bright as can be right now) will reduce the number of active slugs and snails in the veggies. In theory, they should be asleep in their hiding areas, though it’s been so cloudy there may be more daytime feeding activity than usual. You can also just make sure to wash everything particularly thoroughly!

Classic slug damage (here on a hosta). Image from Cornell IPM https://cals.cornell.edu/integrated-pest-management/outreach-education/fact-sheets/slug-and-snail-control

Edema: Waterlogged Woes

Edema is another issue that can sneak up on plants in wet weather like this past month. As plants grow, they pull in water from their roots. Because it’s been so wet, There’s plenty of excess moisture in the soil and ground. And because it’s been so gray and gloomy, the leaves aren’t photosynthesizing as vigorously as they normally would in May. This can create a situation where the roots are sucking in water as fast as they can but there’s no place for it to go at the top of the plant.

Eventually, the plant may be holding onto so much water that pressure builds up and can damage or burst cells. This might make it look like your plant has a terrible disease, when really it’s just drunk up too much water and there’s no other place for it to go. Edema can look like tiny bumps on the backs of leaves all the way up to swollen, calloused, or blistered plant tissue. Edema can later dry into lesion-looking spots that turn brown and corky.

The good thing about edema is that once it gets sunny or dryer, the plants should grow out of it. The only risk is that if edema damages the cells and foliage too much then it can create openings for pathogens to get in and then the plant could become diseased. Think of your plants with edema as a little bit delicate and take extra care watering, handling, and planting them.

Two field examples of edema, on a cabbage leaf and on a tomato stem. Images from U. of Kentucky Plant Pathology Fact Sheet: Edema, by John Hartman and Nicole Gauther https://plantpathology.ca.uky.edu/files/ppfs-gen-18.pdf

Bracing for the Sun

The sun will have to come out at SOME point this summer (right?). However, when the weather does break, now we have a situation where all our plants that have been living in a gray, cool, wet world suddenly have to relearn what light and heat are. Most of our annual plants right now have only seen the sun or dry weather for a handful of days—so if (when?) we switch over to hot, dry weather, they will likely rapidly show stress.

Signs of this stress from sunlight or dry air may include wilting or sunburnt leaves, spindly stems that bend over in the wind or even snap, and wind burn on foliage as the leaves lose moisture to the drier air before they better learn how to regulate this.

Be ready to baby your plants for the first few bright, dry, or hot days. This could include protecting them from the wind and sun, or giving them more water as it’s likely they don’t have very well developed root systems yet. Keep in mind that stress or wind/sun damage may look like diseases, but that healthy plants will often bounce back as they adjust to their sunnier, drier environment!

Flats of peppers being drama queens by 10:30am on the first sunny day after 3 weeks of clouds—note the wimpy stems. These flats were placed under light shade for 2 days and bounced back. Image by Maryellen Sheehan, CCE Madison.

And remember, if you have any plant health questions you can reach out to our master gardener helpline at ccemadisonmgv@gmail.com or give us a call at (315) 684-3001 ext 119. For commercial growers, you can reach out to our ag educators at madison@cornell.edu or (315) 684-3001.