This summer is predicted to be another scorcher, with record breaking temperatures across the U.S. beginning in June. While traditional summer crops do require heat, which is why we wait for summer to grow them, extreme heat waves or heat domes are a different thing altogether.
Plants have a series of behaviors they’ll display when under heat pressure. They can wilt, which is what it sounds like, due to water stress. Leaves will droop, and the solution isn’t necessarily more water, but letting the plant ride out the wave with some shade, if you can provide it. Plants may bolt, which is when they stop growing leaves or fruit and instead, thinking they are at the end of their life, send up a flower, which will quickly go to seed. Once this flower is present, which the plant focuses all its energy on, the fruit and leaves will become bitter. Unfortunately, there’s nothing you can do to “solve” bolting, except pull the plant and start over.
And heat isn’t the only threat: Fruit and leaves can also experience sun scald, which is basically a sunburn. You can see these spots on your tomatoes and pumpkins, which appear white, rather than red like they would on human skin. In most cases, plants will survive sunburn, but it puts the plant under additional stress and makes it more susceptible to other garden threats like disease.
The best solution is to choose plants that will tolerate heat spikes, and then provide some support to your plants by watering evenly, giving shade when you can in the afternoon sun, and not planting, transplanting, or fertilizing during these spikes, all of which are stressful for plants.
Greens that will survive a heat spike
While there are bolt-resistant lettuces you can grow, a true heat dome is simply too much stress, and most lettuce will go to seed. For heat-resistant greens, consider kale, which is hardy in both extreme cold and heat. Collards, known for the greens they produce, are also going to survive a heat wave without wilting, which is why they’re popular across the south. The crop you might not have heard of yet is malabar spinach. While traditional spinach is a spring and shoulder season crop and won’t do well even in an average summer, malabar (which is not actually related to real spinach) is a vining plant from India that tastes remarkably similar and has become popular for its resilience.
Okra and corn are at home in the heat
Considering crops that have been popular in geographies that experience more heat than we’re used to is a good strategy for finding vegetables that’ll survive extreme temperatures. Okra is from Ethiopia, so heat resistance is part of the plant’s DNA. Okra sometimes gets a bad rap for becoming slimy in recipes, but I urge you to consider growing it. There are two varieties of okra: I recommend only planting the spineless variety. The “spines” are spikes that can make touching and harvesting okra painful.
Credit: Amanda Blum
Corn may be a resource hog in your garden, requiring a lot of additional nitrogen to be productive, but it is also highly tolerant. Corn can survive in over 110 degree temperatures and still produce crops reliably, so long as those temperature spikes aren’t extended. A true summer crop, corn needs 70 degree weather to grow, which is why you wait until June to plant corn seed.
Vining plants like luffa, tepary beans, and yardlong beans
To be fair, most people don’t eat luffa (though you can); they know it instead as loofah, a sponge-like material used in “natural” scrubbing. But truly, luffa is a form of vining squash, which will grow prolifically, adores the sun, and thrives in prolonged heat. When the fruit is allowed to dry on the vine, the flesh can be stripped off, leaving behind the luffa, which looks precisely like loofah you purchase, and can be used immediately.
There are plenty of pole beans (beans that climb, as opposed to bush beans, which do not) that originated in hot climates and will do well in a heat wave. Tepary beans, for instance: These beans are native to the Southwest U.S. and Mexico, and will spend the summer climbing and producing pods. Harvest them in the fall before the rain starts, and store them as dry beans.
Yardlong beans are closer to a green bean. Still a vining bean, they can produce beans that are well over a foot long, as their name suggests. These summer stars prefer less water, and they will thrive anywhere they have support, like a trellis.
Soybeans need the heat
While not a vining bean, but a bush bean, soybeans are an easy crop to grow if you’ve got enough heat. These sun-tolerant plants will produce a limited amount of pods per plant, so they need to be grown in groups, but they require almost no support except watering. Harvest the pods and eat the beans steamed fresh, as you would in your favorite Japanese restaurant, or dry them to make soy milk or tofu.
Squash and melons love the heat
There are two kinds of squash: summer and winter. Summer squash includes crops like zucchini, yellow squash, and pumpkins. Winter squash includes crops like acorn squash, butternut, spaghetti, and others. Both kinds of squash are traditionally grown in summer, and both are surprisingly resilient in heat. While you might experience sunburn on some fruit, squash is famous for providing shade due to the large leaves, and they will not only take care of most fruit, shielding it, but will also protect nearby plants by shading them, as well.
So long as you keep your melons apart from your cucumbers and squash so they don’t cross pollinate, your vining melons are likely to survive a heat wave with the same caveats as squash: Look for fruit that is exposed and cover it from sunburn, but the plant will mostly take care of that on its own.
Sweet potatoes are built for high temps
Originally from Polynesia, sweet potatoes are an excellent crop for beginning gardeners. They’re easy to cultivate seedlings (called slips) from any sweet potato you bring home from the store. Once planted, they produce prolific above-ground vines that are showy with flowers, while below ground the potatoes grow over 120 days. These plants not only tolerate but thrive in heat.
