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Thursday, August 22, 2019  Spokane, Washington  Est. May 19, 1883
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Steps to keep lawn alive in heat

Last week I talked about a bunch of pesky lawn insects that survived the winter. This week I am going to talk about caring for your lawn in our record heat.

The key to getting your lawn through heat waves is to water effectively. Bluegrass lawns need 1 to 1.5 inches of water a week and even more with the heat. Sod roots generally grow about 6 inches deep and need enough irrigation to soak the entire root mass. To determine how deep your current watering program is getting, dig a small hole in the lawn and measure the band of damp soil. If it’s not wet down 6 inches you need to water longer.

How long is enough? That is going to depend on your soil type. Sandy soils drain much more quickly than clays; you will need to water more frequently than if you have clayey or loamy soil. Watering for longer and less often will put more water at the root level. I have a nice sandy loam in my lawn and I find I need to run my rotary sprinklers for 45 minutes, three to four times a week to keep it green. Even then I always end up with “rain shadows” caused by trees and other plants that block the spray. Lawns that have turned brown already will eventually green up again, but it is going to take some cooler weather.

It is best to set your sprinklers so they water sometime between 4 p.m. and 10 a.m. You will lose half the water to evaporation by watering in the heat of the day. Watering in the evening and overnight allows the plants to rebuild their reserves. Watering at night here doesn’t create the disease problems found in other parts of the country where the humidity is much higher. Don’t try to hand water a lawn; instead set a sprinkler up on a wind-up timer and let it run for the needed amount of time.

In hot weather, lawns shouldn’t be mowed any shorter than 3 inches. The longer grass shades the soil and helps reduce water loss. This is not the time to have a putting green for a lawn. Set your mower to its highest setting and leave it there until it cools down in September.

Don’t fertilize grass when it’s hot. Lawns naturally slow their growth in the heat and can’t effectively use the nutrients. Fertilizer just adds another layer of stress to the already overburdened lawn. Wait until September to fertilize and then use a slow release fertilizer that greens the lawn up slowly and then keeps feeding it for a couple of months or more.

Hot weather is also not a good time to spray lawns for weeds. The weeds are being stressed by the heat and don’t take up chemicals effectively. Sprays can also volatize and drift onto desirable plants when the temperature is above 85 degrees.

Pat Munts is co-author, with Susan Mulvihill, of “Northwest Gardener’s Handbook.” She can be reached at pat@inlandnw gardening.com.

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