It’s still hot . . . and dry

By Heather Kirk-Ballard

LSU AgCenter Horticulturist

(10/04/19) Temperatures continue to soar in the 90s even though it is officially fall and we are now in October. Even though our evening temperatures are cooling off, we have not had significant rain for several weeks in many parts of the state. And north Louisiana has pockets of drought.

Just take a look around. The plants don’t lie. We see signs everywhere that our plants are suffering. Turfgrass and lawns are browning and beginning to go into dormancy if not just downright throwing in the towel. Herbaceous plants are beginning to wilt and turn yellow. Leaves are beginning to fall from trees — not because it’s fall but because they’re trying to conserve water.

Weeds are beginning to move into our lawns and take over. Insects and diseases will take notice, too. It’s a vicious cycle. We need relief soon. Thank goodness the weather forecasters are predicting a cold front and chance of rain in our near future.

So how do plants combat a shortage of water coupled with temperatures approaching 100 degrees? Plants’ first line of defense is closing their stomata — pores found on leaves, stems, etc. Plants cool themselves through a process in which water is evaporated from pores, carrying the heat out and away from the plant in the process, but thereby losing water.

What happens next?

The next line of defense is wilting. Eventually, plants drop their leaves as a survival mechanism and go into dormancy to conserve everything they have. Once they have been affected, plants are susceptible to secondary attacks by disease and insects. Long-term damage can cause stunted growth, dieback and eventual death of even very large trees.

Despite all of this doomsday talk, I have good news. We can do many things to prepare for dry conditions.

When planning new landscapes, select plants with the right stuff. Plants differ in their use and requirements for water. Some are tougher than others. Succulent plants, especially sedums, cactus, yuccas, aloe vera, crown of thorns and kalanchoe, are examples.

Ornamental grasses are another great example of drought-tolerant plants. They are just showing off right now with all of their gorgeous flower spikes, or plumes. They don’t seem fazed by the drought at all. Some commonly used ornamental grasses for Louisiana landscapes are zebra grass (Miscanthus sinensis Zebrinus ); pampas grass (Cortaderia selloana); Fireworks fountain grass (Pennisetum setaceum Fireworks), a Louisiana Super Plant; pink muhly grass (Muhlenbergia capillaris); panic grass or switchgrass (Panicum virgatum), a native Louisiana plant. All are suited for our USDA hardiness zones.

In general, many natives tend to be the most drought tolerant plants for the landscape because they have adapted to our climate. No one can predict just how long droughts and heat will occur, and we know they will happen from time to time. We can plan and plant for just this occasion. If things continue as they are, we will continue to see swings in water availability in the years to come.

Choosing drought-tolerant plants and native plants is a good place to start. Where you plant them is also important. Plants that are growing under the canopy of a large tree are the first to wilt because they are no match for the extensive root system of trees. The International Society for Arboriculture says the root system compared to trunk diameter is 38 to 1, so a 6-inch-diameter tree would have roots 19 feet out from the trunk.

Turfgrasses especially tend to suffer. It’s a good practice to steer clear from planting grass in the root zone of large trees.

Incorporating organic matter into your soil, applying mulches to garden beds, weeding regularly and applying supplemental watering during droughts will help dramatically. The best time to water during drought and hot weather is early morning and late evening. By watering at these times, you will cut down on evaporation and allow the plants several hours without sun to take up the water into their system. Infrequent but deep watering is best. Set up soaker hoses or drip irrigation for watering at these times.

October is traditionally one of the driest months in Louisiana. It’s not going to get better soon on the rain front, so get out there and help your plants while we wait for shorter, cooler days and nights and the forecast for a chance of rain and a cold front that gets here in the nick of time.

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Plants under large trees suffer first during periods of dry weather and drought. Photo by Heather Kirk-Ballard/LSU AgCenter

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Pink muhly grass provides a colorful display in fall. LSU AgCenter file photo by Allen Owings

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Plumes of pampas grass continue their display despite dry conditions. Photo by Heather Kirk-Ballard/LSU AgCenter

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Zebra grass sends out showy plumes in fall landscapes. Photo by Heather Kirk-Ballard/LSU AgCenter

10/4/2019 4:14:09 PM
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