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Brock: Summer heat signals stress

Summer is now officially here, and it’s officially real darn hot outside. This time of year you’ll rarely find me outside in the middle of the day if I’m not in a pool, pond, creek, or bayou. I bet you feel the same way, and I can tell you your plants do too.

Summer heat is stressful on most plants, even those well-adapted to this kind of climate. But before we address their needs, let’s use some common sense to address our own. When gardening in summer, it’s best to keep most activity to early morning and late evening. Wear sunscreen, stick to the shade when possible, and drink lots of water.

Heat stroke is a serious condition, but less-severe heat stress is much more common. Take frequent breaks from yard work and watch for signs of heat stress. These include excessive perspiration, clammy skin, and sometimes dizziness.

So what about the plants? Their signs of heat stress will include wilting, yellowing, and lack of production (for fruits). Usually watering will cure it; do so with appropriate frequency and depth. Vegetable gardens want water about every 2-3 days when it’s not raining. And bear in mind any single rain event less than one inch will not get to your plants’ roots. Always water slowly and deeply; try not to wet foliage.

Lawn grass is best watered once a week. Place a rain gauge in the yard when watering, assuming you’re using a sprinkler. See how long it takes to get to an inch or more of rain equivalent. Now you know how long to water the lawn each time; again it should be done weekly. If it’s too frequent, there’s an increased chance of disease. Watering any plants in the morning is also a good way to avoid disease. If leaves stay wet overnight, it’s asking for a fungal or bacterial infection.

Watering plants in pots is simple, but will be needed more often. I can’t give you a timetable for this one, since so many factors go into it. These include plant species, type of pot, size of pot and plant, sun vs. shade, etc. Just feel the soil now and then and keep it somewhat moist. If plants begin to shrivel, you’ve waited too long; do better next time. And whenever watering pots, give enough so that water leaks out of the pot’s bottom holes.

Potted plants may also be moved into more shade if hydration is a challenge. Something grown in full sun in spring may now be stressed in the same place. Try and get the plants where they’ll at least have a break from the most intense mid-day heat. And choose morning sun over afternoon/evening sun when possible, since the latter is more intense.


Signs of heat stress in plants can include wilting, yellowing and lack of production

Of course, choosing the most heat-tolerant plants will help. Okra can still be planted in July, as well as cucumbers. We can plant fall tomatoes now, too; just be sure they’re heat-set varieties like Bella Rosa or Phoenix. Cauliflower can also be planted starting this month, but it will require a lot of attention and hopefully some shade setup that can be removed later.

Heat-loving ornamentals include sunflowers, zinnias, and cosmos. These can be planted from seed. Remember that any seeds will dry quickly, so they need attentive watering too.

If you want to know more about gardening, landscaping, or anything else horticultural, contact the St. John, St. James, & St. Charles Parishes County Agent André Brock at abrock@agcenter.lsu.edu. Also, the LSU Ag Center’s website can be accessed at www.lsuagcenter.com with lots of user-friendly information, including this article.