By dl91m on es.wikipedia (Own work) [Public domain], via Wikimedia Commons
Growing up in Utah, I heard the term “flash flood,” all the time. That meant if you were hiking a slot canyon in the desert and spied a dark cloud out of the corner of your eye, you scrambled out of there as fast as your hiking boots could carry you, so you didn’t get swept to your death like a spider down a bathtub drain.
But “flash drought,” defined as “a sudden, unexpected burst of high temperatures and low humidity,” was a term I had never heard until a month ago, when a friend of mine who works in horticulture was lamenting that people were complaining about their plants dying—because they didn’t realize they had to water them. Which might sound silly, until you think about how often, and how copiously, it rained around here even 10 years ago. So, what the sky used to do for us we now have to do for ourselves.
We’re guessing your garden is already installed for the year—and that you’re not about to rip out all your maturing plants to install a drip-irrigation or soaker-hose system—but there’s really no other way to go, unless you are a container gardener. Wet, muddy leaves are great at sparking disease in plants, and that’s exactly the conditions those fanning sprinklers create. So if you are still part of the hand-held hose brigade, water in the early morning rather than during the heat of the day (when of course it evaporates) or at night, when darkness and cooler temperatures, combined with moisture, can promote mold and mildew.
The other reason to water in the cooler morning: watering heat-stressed plants stresses them out even more, especially if temperatures are over 100 degrees. Be careful not to overwater, because this will stress the plant out, too—if the soil by the roots is moist, you're OK. If you have room to do it, you can supply shade to your plants to give them a break from the sun during extreme heat days.
Of course, the other part of this equation is being smarter about planting drought-resistant plants. (In case you haven’t noticed, turfgrass is not a drought-resistant plant.) You can find species that are better suited to Missouri’s climate—and hence less likely to succumb to flash droughts—on the Missouri Botanical Garden’s Plants of Merit list. And if you are not mulching, start now! Newspaper and straw works well. But be sure to put it down in the morning, before it gets hot, and makes conditions tough not just for plants, but for gardeners, too.
