Are your plants wilting in the heat? More water may not be the answer

Photo by Wendy Hanson Mazet.

Temperatures are soaring, reaching record-breaking highs. Though we can run for the relaxing comfort of air conditioning, our plants must cope with the conditions. Some plants do well in this weather and do not show any signs of heat stress, often because they are native plants, which are adapted to a dry, hot environment.

Unfortunately, the large majority of plants we choose to put in our yards and gardens are not accustomed or well-adapted to triple-digit temperatures. Without much-needed shade in the afternoon cast by buildings or established trees, these plants may fade, wilt or, in the worst case, die from the extreme heat.

Even when soil conditions are ideal, which includes adequate moisture, many plants will wilt or droop in the heat. The wilting process is caused by plants losing moisture through their leaves. This is a natural process called transpiration. Transpiration is the movement of water from the roots throughout the entire plant and its leaves. When environmental conditions cause a plant to lose more moisture from its leaves than the plant’s roots can supply, the plant will wilt.

For gardeners, the challenge is to find out if the wilting is caused by water stress or heat stress. A way to do this is to check the soil moisture before adding more water. Plants that have adequate moisture may wilt in the daytime temperatures and revive without assistance as the temperatures drop in the evening and the plant’s system balances out. If you were to start adding extra water to an already moist area, you may end up drowning your plants, starving their roots for oxygen and causing them to die.

So, take the time to go out and observe. In the mornings, take a small trowel with you, and check the soil’s moisture near your plants. In our high-desert climate, the heat and wind will pull moisture out of the top 1 inch of soil within hours. Because of this, you should check 2 to 3 inches deep near plants before deciding to give them any more water. If you see moisture at this depth, you may not need to provide extra water.

To reduce summer stress on landscape plants, make their environment more hospitable by changing how you water them and by applying compost.

Very few plants need daily watering if they are encouraged to grow a large root system in which the majority of the roots are found at least 6 inches below the soil line. To encourage good roots systems, water plants deeply and widely. For already established plants, water deeply and less frequently. Modify your irrigation and check it regularly.

Improve the soil conditions of your plants when you plant them by incorporating compost into the top 6 inches of soil. If you have an existing landscape, add compost as a mulch around your plants. Compost will not only keep the soil temperatures cooler for the plants, but it will also feed the soil which will ultimately feed your plants.

Wendy Hanson Mazet is a horticulturist and certified arborist with University of Nevada Cooperative Extension. Have questions about your plants? Contact a Master Gardener at 775-336-0265 or, or visit