Keeping our gardens watered in the heat is one thing; however, heat can also cause some problems.
Do remember that certain vegetables are COOL season plants—radishes, lettuce, carrots, beets, broccoli, cabbage, kale, etc. They are not going to do well in hot weather, period, no matter how well you take care of them. Other plants don’t mind the heat so much, but excessive heat can cause some problems. Temperatures in the 90’s can cause some plants to abort their flowers—tomatoes are famous for this, but other tomato family members can also do the same thing—peppers and eggplants. Green beans have been known to hold off on bean production until the weather cools back down into the upper eighties and lower nineties, and cucumber family members can actually produce more male flowers than females (so less fruit) in excessive heat.
Another problem we can have is powdery mildew. This fungus thrives in hot and humid weather, so keep an eye out for white “dusty” looking patches on leaves (particularly on cucumber, melon, and squash foliage, which is prone to it). To help prevent it, always give your plants as much room as the seed packets or plant tags tell you. Good air circulation is crucial.
A spray (believe it or not) of 40% milk to 60% water has been shown to be very effective at the fungus that causes powdery mildew or you can always use Neem oil.
Now, if excessive heat persists more than a day or two, you may want to invest in a light shade cloth. Be sure to suspend it at least a foot or more above your plants so as to allow plenty of air circulation. And, if your problem with powdery mildew persists, you may want to hold off on fertilizer since powdery mildew loves tender new growth.
And lastly, when watering, water at the base of the plant. We don’t need to compound the problem with adding our water to 80% humidity. Soaker hoses come in handy here—watering your plants at the roots where they need it. It may even save you a bit on your water bill—because less water evaporates.