Protecting Crops from Heat Stress

This week, major heat waves are hitting much of the East Coast and Midwest. We hope everyone finds a cool place to rest and stay safe this summer. However, we also realized that many gardeners are probably struggling with heat stress in their plants during this time. While we can’t move our whole garden into the air conditioning, we can do a few things to help protect our crops from extreme temperatures.

Check Plants Often

Keeping an eye on your plants and spending some time in the garden whenever it’s cool enough, like early mornings or late evenings, can help prevent stress and catch any issues early.

One thing you want to keep on top of even though it’s tough in hot weather is weeding. Weeds often compete with crops for moisture and may prevent adequate air circulation.

You should also harvest often. Picking crops before they are overripe will prevent plants from wasting energy. 

You should also watch for signs of heat stress, such as fruit or blossom drop, curling or yellowing leaves, and wilting. If you see these signs, consider taking some of the steps outlined below. 

Maintain Proper and Consistent Watering

Consistent moisture is essential for good production and plant health, especially during high temperatures. Inconsistent watering can result in heat stress symptoms like curled leaves, poorly formed cucumbers, splitting tomatoes, and more. 

Ideally, you should water in the early morning or evening. If you water during the middle of the day, much of it will be lost to evaporation.

How you water also matters. Overhead watering leads to much more evaporation than directly watering the soil around plants. If possible, use soaker hoses or drip irrigation. For small gardens where you hand water, try to direct the water to the base of the plant. 

Especially during hot weather, deep watering can be helpful. Aim to water at least two to three times per week, getting a total equivalent of about 1 inch of rainwater to your crops weekly.

Generally, it’s tough to provide too much water during hot weather, but keep an eye on your soil and avoid overwatering. Soggy soil can lead to root rot and fungal diseases.

Container plants will dry out much faster and need extra attention and watering. 

woman using scythe with greens and onions growing in the foreground
Wood chips make great mulch for preventing heat stress and you may be able to find them for free.

Mulch

We talk about mulch a lot on this blog, but it really can make a big difference when it comes to heat stress. A few inches of mulch, such as straw, pine needles, old leaves, grass clippings, or wood chips, can decrease soil temperatures dramatically. It also helps block weed growth and keeps the soil moist.  

Further, mulch can prevent soil from splashing onto the leaves of crops like tomatoes, which are highly susceptible to soil-borne fungal diseases like late blight. 

Provide Shade to Prevent Heat Stress

While plants need a certain amount of sunlight to grow, they’re generally too stressed during the hottest parts of the day to do much growth anyway. Providing some temporary shade, particularly during the afternoon, can be helpful.

For small gardens, you may be able to use what you already have on hand. Consider using patio umbrellas, EZ Up canopies, or shade sails to offer your plants some temporary respite from the afternoon sun. 

Alternatively, you can purchase shade cloth or row cover and use it over plants. We often use row cover at SESE to keep out pests, provide shade for cool weather crops, and provide a little frost protection for fall crops. Old sheets or other materials and scrap pieces of fencing could be used for a similar effect.

If possible, move container plants to where they will receive morning sun and a period of afternoon shade. 

Avoid Fertilizing

When gardeners see plants looking rough from heat stress, they sometimes mistake the signs for a nutrient deficiency.  Unfortunately, fertilizer does more harm than good during periods of extreme heat. 

A boost in nitrogen and other nutrients signals to plants that it’s a good time to put on new leaf growth. We don’t want plants that are already overtaxed from the heat trying to make new leaves! Focus instead on watering, weeding, and harvesting to improve plant health.

Case Knife Pole Snap Bean
Case Knife Pole Snap Beans are less susceptible to heat stress than some varieties.

Plan for a Heat Stress Resistant Garden Next Season

If heat stress is a major struggle for you this season, it’s a good idea to incorporate that into next season’s garden plan. Maybe you need to keep more mulch on hand, invest in soaker hoses, improve the soil, or focus on more heat-tolerant crops. 

Improving your soil can help it hold moisture better. To do this, you need to add organic matter. Cover cropping is a great option, as is adding mulch and several inches of finished compost whenever possible.

Even among cool-season crops, some varieties are more heat tolerant than others. Here are a few of our favorite varieties for when temperatures soar:

There are many other great options. When selecting your favorite crops, do some digging and check for varieties that mention heat and drought resistance. In our catalog and on our website, you can see varieties with a sun symbol. This means that they are especially adapted to the Southeast. 

Keeping your garden healthy and productive during heat waves can be a major struggle. Using these strategies when the temperatures climb can help you keep your garden in top shape during the hottest summer months. 

Beneficial Insects: Fireflies

Let’s talk about fireflies! These beautiful insects enamor kids and adults alike. It’s hard not to love how they light up the night, but there’s more to fireflies than beauty! They are wonderful for gardens. They’re native predators that feed on common garden pests like slugs and snails. Keep reading to learn about some firefly species you might see, their lifecycle and benefits, and how to attract them to your garden. 

Firefly Species of the Southeastern United States

The name firefly doesn’t refer to a single species. There are over 2,000 species of fireflies worldwide, and about 175 are native to North America! Here are some of the incredible firefly species you might see if you live in our region, the Southeastern United States:

  • The Common Eastern Firefly or Big Dipper Firefly (Photinus pyralis)
    Males produce a single sustained yellow light, often in a J-shaped flight trajectory.
  • The Blue Ghost (Phausis reticulata)
    Males glow with a pale blue or green light rather than flashing.
  • The Synchronous Firefly (Photinus carolinus)
    All individuals in an area will display 5 to 8 flashes of yellow light followed by a period of darkness for 8 to 10 seconds.
  • Father Mac’s Firefly or Mr. Macs (Photinus macdermotti)
    Males display two flashes of yellow light about 1 1/2 to 2 seconds apart, followed by 4 to 5 seconds of darkness, then another double flash.
  • The Spring Four-Flasher (Photuris versicolor var. quadrifulgens)

    These fireflies display in spring with a stuttered four-part flash. 

Next time you watch fireflies, see if you can spot any recognizable flash patterns! Of course, there are also many other species of fireflies you can learn to identify. Finding an insect field guide can be helpful (check your local library), or check out resources that the Firefly Atlas has listed.

Blue Ghost Firefly
Aggyrolemnoixytes, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Beyond Beauty: Understanding Fireflies

While you might already want to attract fireflies to your garden just for their looks, there are a few other reasons they’re great to have around.

Fireflies have a four-part lifecycle: egg, larva, pupa, and adult. The entire lifecycle can last two months to three years, depending on the species, with the longest period spent in the larval stage.

Firefly larvae live in moist soil, feeding off slugs, snails, and other soft-bodied insects. They’re an excellent garden ally! All firefly larvae are bioluminescent, which may help ward off predators.

After that stage, they pupate in safe spots like underground, rotting logs, or bark furrows. They overwinter in this stage and emerge in the spring as adult fireflies that light up the skies. Depending on the species, adult fireflies may feed on nectar, pollen, other fireflies or not eat at all.

Not all adult fireflies produce flashes. In those that do, the flash is made by chemicals like luciferase and luciferin, working with other substances in the insect’s body to produce light in the firefly’s lantern organ on their abdomen. 

The flashes, often created by males while flying, are signals to find mates. Different species have different flash patterns and sometimes different colors so that they can find a mate from the correct species.

Thanks to fireflies, scientists have created a test for harmful bacteria like salmonella or E. coli in food products such as milk, soft drinks, and meat. The test contains luciferase and luciferin, which react with any ATP found in bacteria cells (and all living cells). A glowing test means bacteria is present.

How to Encourage Fireflies in Your Garden

Unfortunately, many firefly species are in decline. They have been affected by habitat loss, climate change, and pollution. Now that we have some basic knowledge about the firefly lifecycle, we can consider what would make our gardens and yard attractive to them. 

Avoid Pesticides, Herbicides, and Other Chemicals

Some of this goes without saying; obviously, spraying your garden and home with pesticides is detrimental to all the species that live there. Pesticides (even organic ones) don’t discriminate between good bugs and bad. 

Other chemicals, such as herbicides and fungicides, can also linger in the soil, affecting firefly populations for years to come. Always thoroughly research any product you intend to use in your garden.

Synchronous Fireflies
Firefly Photos by Radim Schreiber; FireflyExperience.org, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Improve Soil Health

Much like your plants, firefly larvae thrive in rich, moist, loose soil with plenty of organic matter. Good soil isn’t built overnight, but there are many free or cheap ways to improve it. Consider adding compost and leaf litter to your garden. You can also use methods like broad forking, no-till gardening, and cover cropping. 

Natural Spaces

Even if you nurture a suitable habitat in your garden, it’s always a good idea to consider keeping some space wild if you have a suitable property. Rotting logs, leaf litter, and weedy native plants may seem unsightly to some but are attractive to our firefly friends and other native species. 

Minimize Outdoor Lighting

Many scientists believe light pollution interferes with firefly mating and probably contributes to their decline. Minimizing outdoor lighting at night can give those in your area a better chance. Plus, it also helps migrating birds!

Consider closing curtains in brightly lit rooms and turning off outdoor lighting when not in use. You may also consider switching to motion detector lighting for the outdoors, which can still help with security and provide automatic light whenever you need it.

Don’t Remove Leaf Litter

Leaf litter provides an essential habitat for fireflies and other beneficial insects. When you rake up leaf litter, you remove organic matter from your soil and rake up firefly larvae!

Leave Riparian Areas Natural

Don’t mow near the edges of ponds, creeks, and rivers any more than you have to. A small patch for access is fine, but mowing the whole thing eliminates habitat and contributes to erosion and water pollution. 

Plant Native Species and Encourage Variety

When possible plant native species to support all kinds of native wildlife and insects. You can also improve the habitat, even in areas where you are growing non-natives, by encouraging diversity. Avoid aggressive invasive plants and monocultures. Instead, opt for a mix of plants with varying heights, textures, and blooms.

Fireflies bring a lot of joy and purpose to your garden. Help them thrive by keeping these practices in mind this season.

Organic Slug Control

Many of our customers occasionally struggle with pests. Unfortunately, they’re a part of gardening! One common issue we see, especially in spring and early summer, is slug damage. These slimy little creatures are active at night and during cool temperatures, snacking on your plants, especially young, tender foliage. They can take out entire seedlings or reduce your harvest from tasty crops like tomatoes and strawberries. Learn how to identify and combat a slug problem with organic methods. 

Signs of Slugs

  • Shiny slime trails across leaves and the ground.
  • Irregularly shaped holes in leaves, flowers, and fruit.
  • Look for slugs at night or on rainy days.
  • Look for slugs under lower leaves, boards, and other cool, moist shelters.

Deter Slugs

Slugs thrive under certain conditions. To prevent them from becoming an issue, avoid making your garden an attractive habitat for them. 

Here are some ways to deter them:

  • Prune lower branches and foliage to encourage air circulation and sunlight.
  • Stake plants like tomatoes to encourage air circulation and keep fruit off the ground. 
  • Divide or thin plants to encourage air circulation and sunlight.
  • Remove natural mulch, like old leaves, at least temporarily.
  • Add compost to beds, improve soil, and improve drainage to help combat wet conditions over time.
  • Remove places where slugs could hide, like containers, flats, stones, boards, etc.
  • Use water-wise gardening techniques like drip irrigation or soaker hoses to minimize excess moisture. 
European Starling
European Starlings are not native to the U.S. but are common in the southeast and are incredible slug predators.

Attract Predators

In the long term, attracting slug predators can also be an effective way to manage slugs. We think they look a little slimy, but many creatures, such as slugs, beetles, toads, turtles, snakes, ducks, and certain songbirds, find them to be a tasty treat. Providing habitats for these animals within your garden can encourage them to stay and eliminate slug populations.

Handpick or Trap Slugs

One of the simplest ways to get rid of slugs is to handpick them. Put on some garden gloves and head out at night with a flashlight for a bit of slug hunting. Then, crush the slugs or toss them into a bucket of soapy water.

While we previously mentioned getting rid of slug homes like boards, you could add them to make the perfect trap. Each morning, flip your board and kill any slugs you find. 

Another classic method for dealing with slugs is the good old-fashioned beer trap. Take small containers or dishes and bury them a bit in the garden so the top is level with the ground. Then, fill them with beer or a water and yeast mixture. The slugs will be attracted to the beer or yeast mixture, fall in, and drown. If you have a serious problem, you may need to put out a good number of traps and change them daily.

Organic Slug Baits & Deterennts

Coating plants with a heavy dusting of diatomaceous earth can help keep slugs at bay. However, it must be reapplied frequently and isn’t always a great long-term solution.

Copper foil or bands are another effective slug deterrent. While they can easily be affixed to a single raised bed, they may not be an efficient choice for large gardens.

You can also purchase organic baits like Sluggo, which is OMRI-certified. If you want to use slug bait, this is a good option because it’s safe for pets and non-toxic. It’s made from iron phosphate.

Many other slug baits are toxic to other animals, including pets and young children. Always select and use garden products carefully.

We always aim to work with nature to create beautiful, bountiful gardens. Unfortunately, pests will always be an occasional issue in any garden, whether organic or conventional. Thankfully, slugs are a relatively easy pest to deal with, and you can use these simple strategies to deter and eliminate them.

Saving the Past for the Future