Summer Heat Stress

The heat of summer makes me want to seek shade and drink a tall glass of water. The same is true for our lawn and garden plants. Unfortunately, our plants can’t lounge under an apple tree to escape the mid-day sun. But you can help them out by adjusting your irrigation, misting them with water and mulching your soil.

Now is the time to reprogram the timer for your lawn sprinkler system. It is probably running on the same settings you or your landscaper set in May. This is simply not enough water. To figure out by how much you should increase the time, check out the Washoe County Evapotranspiration Web site http://www.washoeet.dri.edu. This Web site will tell you, based on current weather conditions, how long you should run your lawn sprinklers on your assigned watering day. It even breaks down the watering time based on sprinkler type (pop-up, impulse, or rotor). If you know the weather forecast will hold for the next few weeks, go ahead and reprogram your timer to run for the time shown for your sprinkler type. Remember to split your water time up into 3-5 cycles. Turf grass grows best when it is watered with in short (10-15 minutes) bursts with an hour in between each cycle.

The opposite is true for trees, shrubs, perennials, annuals and vegetables. Ideally all of these plants should be on a drip system that can turn on independently of your lawn sprinklers because these plants benefit from less frequent, deeper watering. During the heat of summer, deeply water your trees and shrubs about once a week, perennials about twice a week, and annuals and vegetables about three to four times a week. Deeper soaking encourages deep root growth and allows plants to draw water from deeper in the soil. The best way to determine how much and frequently to irrigate to is stick a 10-inch screwdriver into the soil. If it goes in easily, your soil is probably moist enough. If it meets resistance, it’s time to water.

If you properly water your plants and they still sag and wilt, spray or mist the leaves during a cool time of day. The water will cool the leaves and increase the plant’s efficiency at drawing water up from the soil. If you are going to use your garden hose, be sure to let the water run on the lawn until the water cools so that you’re not spraying hot water on already heat-stressed plants.

In the heat of the summer it is also important to reduce the amount of water lost from evaporation. Many people are surprised to learn that water can be wicked up and out of the soil through evaporation. To reduce soil evaporation, cover your soil with an organic mulch, such as wood chips, compost or straw. Put down at least 3 inches of mulch, taking care to keep it 3 inches from the plant bases. The mulch will help keep the soil cool and moist, as well as suppress weed growth.

Even though your plants can’t seek shade in the middle of the day, you can provide them with a reprieve from summer’s heat. Remember that properly watered lawn and garden plants will be more resistant to insects and disease. Making regular monthly adjustments to your irrigation throughout the summer will keep your landscape vibrant and beautiful.