Intense heat may stress your plants

Experiencing such hot weather in June surprised me. How can you tell if a plant is heat stressed?

The first sign is wilting, which makes the plant look droopy. Wilting usually occurs because of a lack of water. A plant can also wilt when it is so hot that the plant cannot absorb water fast enough to compensate for the high temperature, even though there may be water in the soil.

Dry winds exacerbate the wilting process. The wind blows across the surface of the leaves, drying them out. The plant responds by trying to pull more water up from the soil, like a thirsty person sucking up water through a straw.

Another sign of heat stress is brown or burned-looking edges of leaves or needles. Maples and aspen are known for exhibiting this. When a plant can't get enough water up through its vascular system (the straw) to supply all the cells of the leaves, the edges or leaf margins start dying off.

Even lawns wilt. This week, my lawn lost 2.5 inches of water. Did your irrigation system apply 2.5 inches of water last week? To find out how much water your system is supplying, put coffee mugs or cans on the lawn and run the sprinkler system 15 minutes. Measure the water in the cans, and then you will know how much water the sprinkler applies every 15 minutes.

For example, if a one-quarter inch of water is in the can after running the sprinkler for 15 minutes, and your sprinkler runs 30 minutes per week, the lawn is only getting one-half inch of water per week. That is not enough water in this heat.

To help reduce heat stress, water trees and shrubs separately from lawns. Water them to a depth of 15 inches from the trunk out to the end of the branches. Place 3 inches to 4 inches of mulch around all plants. This will help hold moisture in the soil, rather than allowing it to evaporate with exposure to wind and sun. Water during the coolest time of the day, and never during the middle of the day.

Avoid planting new trees, shrubs, flowers or lawns during the summer months. Fall is a great time for planting.

In Carson City, water restrictions are now in effect until Oct. 1. Those with odd-numbered addresses may water their lawns on Tuesday, Thursday and Saturday. People with even-numbered addresses water on Sunday, Wednesday and Friday. All watering is prohibited on Mondays. In addition, watering is to be done before 10 a.m. or after 6 p.m.

For more information, e-mail skellyj@unce.unr.edu or call me at 887-2252. You can "Ask a Master Gardener" by e-mailing mastergardeners@unce.unr.edu or call your local University of Nevada Cooperative Extension office. Check out many useful horticulture publications at www.unce.unr.edu.

• JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension.