It’s too hot for tomatoes

Published 9:32 am Tuesday, August 4, 2015

By Terry Rector

Somebody asked why his tomato plants have very few tomatoes right now but he already knew the answer; August. The hot weather is the culprit and it is two-fold. First, all plants’ pollen has a “dying point.” It’s just that tomato, like cotton and other sun worshippers, has a higher tolerance for high temperatures. But somewhere up around 95 degrees and up, tomato pollen is subject to dying and failing to pollinate blooms. Long gone sweet corn and snap beans have lower pollen-killing temperatures than tomatoes which is why they are long gone. And keep in mind the temperatures reported on TV and online didn’t come directly from your garden or containers. Yours might have been a tad cooler from midafternoon shading or a tad and a half hotter if your container garden sits along the concrete driveway.

Though we don’t chat it up like daytime highs, nighttime temperature affects plants, too. When overnight lows don’t drop below 75 or so, hot weather annuals like tomato can suffer loss of fruit. Simply put, a plant has to put so much of its “umph” into air-conditioning itself to cool down on schedule it is subject to shedding existing blooms and small fruit. Remember, whenever a plant is in any severe stress, it goes into a survival mode and to heck with the reproductive mode.

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We tend to think of “hot and dry” as one in mid- to late-summers because ours usually are both. The difference is we can do something about the “dry” but not the heat. Proper watering prevents the additional stress of soil moisture shortage. And it is important to keep the water coming on vegetable plants such as tomato when needed even when heat is killing pollen. If we can keep even fruitless plants alive now, September and October tomatoes will happen. Granted, we might have to keep some fungal diseases at bay also, but tomato plants actually want to live until a freeze does them in. The goal of watering plants should be to maintain soil moisture as evenly as possible and avoid the range of extremely dry to extremely wet. That was an important lesson I learned from a soybean irrigation demonstration project we conducted years ago in north Warren County. If you are going to the trouble and expense of watering crops, don’t wait until the ground gets dry to turn on the faucet. Keep the ground from getting dry in the first place.

Finally, there is one thing every August tomato plant should have that helps prevent the stress of dry soil and helps cool the root zone: MULCH, and don’t be a skimpy tightwad about it.

Location Change: The site of Stephan Kirkpatrick’s wildlife photography presentation Thursday, Aug. 13 has been changed from Hinds CC to the Vicksburg Auditorium downtown. This is the main attraction of the Warren County Soil and Water Conservation District annual dinner meeting beginning at 7 p.m. The cost is $15 for catered catfish. Reserve a spot by calling 601-636-7679. Extension 3.