Many vegetables we think of as heat lovers, like tomatoes, peppers and beans, stop flowering and producing fruits, when temperatures remain hot for extended periods.
Most vegetable gardeners are aware of a vegetable’s temperature requirements for germination. We know peppers like bottom heat (75 – 85 F.) and lettuce and radishes grow best in cooler soil, but I always expected my hot weather crops to love the hazy days of summer.
If you’re tired of being disappointed when summer temperatures go to extremes, look for varieties labeled as either “Heat Tolerant” or “Drought Tolerant”. Of course, we also have the humidity to contend with, so we should also be on the lookout for varieties that have some fungal disease resistance. Sometimes that means growing an entirely different species. For instance, regular green beans will stop flowering during prolonged heat or drought, but yard long beans can handle these conditions. My ‘Chinese Red Noodle’ beans don’t really start producing until August, but they continue right up until frost.Tomatoes are notorious for dropping their flowers. Although there can be other causes for this, like overly heavy fruit set or underfed plants, very often it is simple high temperatures. Those heat waves when temperatures remain in the 90s for days don’t just affect people. Tomatoes can’t handle the stress either. The problem is compounded if it doesn’t cool down at night. They will drop their flowers if the thermometer remains above 104 for even a few hours.
What Can You Do About It?
Be patient. I know, it’s hard. We can’t control the temperature. We can provide some temporary shade, with some type of screen. Watering can help cool things down temporarily, but don’t be tempted to overdo it. You could make matters worse by inviting fungal diseases.
Since I never know what kind of weather summer will bring, I tend to choose varieties with different preferences. I’ll plant some quick varieties, that can handle cool, damp weather, and some that like to linger until summer kicks in.
And finally, take some comfort in knowing it is just a temporary lull and enjoy those vegetables that really do love the heat, like eggplants and okra.
Some Heat Tolerant Choices
These varieties can handle heat better than most, but even they will need a little respite during heat waves.
There’s a reason the amazing ‘Kentucky Wonder’ and ‘Blue Lake’ green pole beans have become classics. They are reliable performers throughout most temperature fluctuations. Another that has been a stalwart in the worst of summers is the purple streaked heirloom ‘Rattlesnake’.
Cukes may be a tropical fruit, but a heat wave is not the same as a tropical climate. The plants seem to know they can’t sustain fruits during persistent heat and stop setting female flowers. What fruit does form can quickly become bitter and often grows misshapen, with a bulbous tip like a gourd. I’ve had the best luck with Asian types, like ‘Kyoto’ and ‘Suyo Long’.
Eggplants truly are heat lovers, but even they are not immune to stress from extreme heat. However, even if fruiting diminishes, it doesn’t usually stop entirely. If you like the large orbs, ‘Black Beauty’ is a good choice. And just about any of the long thin varieties, like ‘Louisiana Long Green’ or ‘Ping Tung’ should be fine.
For some reason, chile peppers do better in heat than the sweet ones. Sweet peppers react to that 90 degree blossom dropping mark and they are also negatively affected when nighttime temps remain above 75 F. Look for varieties bred in either California or somewhere in the South, like
‘Carolina Wonder’, ‘Charleston Belle’ or ‘Gypsy’. These tend to need a longer season, but hopefully you short-season gardeners will be spared the heat.
Tomatoes are particularly touchy in heat because of their proclivity toward fungal problems. The University of Florida has done a lot of work in breeding tomatoes specifically for hot, muggy areas and some of their resulting varieties, like ‘Tropic VFN’ hold up quite well. Some other to look for include: ‘Phoenix’ and ‘Picus’. If you like heirlooms, ‘Arkansas Traveler’ is a good choice and I can’t say enough about ‘Cherokee Purple’.
❦ Zucchini and Summer Squash
Summer squash plant grow and yield fairly quickly, which means you can re-plant every month and hedge your bets, whatever the weather. For even more security, try a short-season variety, like ‘Eight Ball’ or ‘Sure Thing’. The heirloom ‘Tromboncino’ is a wonderful alternative to traditional zucchini. ‘Tigress’ has great disease resistance, for long, humid seasons.
Winter squash (Cucurbita moschata) has less problems and actually seems to enjoy intense heat.