Our unusually cool spring weather has slowed down our gardens a bit, but lawns are looking pretty good. However, once hot weather arrives, a few problems probably will start appearing. Here are some tips on how to keep your summer lawn healthy and looking good:
When the temperatures climb, dry spots in lawns often appear. Investigate the causes rather than increase the frequency of your watering. Possible causes include poor sprinkler coverage, compacted soil, buried objects like rocks or construction waste, or hydrophobic conditions.
Sprinklers: To check coverage, place empty straight-sided cans inside and outside of the dry spot. Run the sprinklers for a set amount of time, and then compare the amount of water in the cans. If there is less water, determine the cause and fix it.
Soil: Stick a long screwdriver into the soil to check for compaction and buried objects. If compaction is a problem, aerate the area with core aerating equipment.Hydrophobic: It means the lawn or soil resists wetting. This can be caused by excessive thatch that has dried out or a soil that is hydrophobic. Check for thatch. If the thatch is greater than one-half inch think, power rake next spring.
To help water penetrate in areas of the lawn that are resisting wetting, core aerate to physically open the grass and soil. Then apply a horticultural wetting agent, which is a nonionic surfactant chemical that breaks the surface tension of water and helps the water penetrate the hydrophobic thatch or soil.
Monterey Lawn & Garden sells a wetting agent mixed with fertilizer for lawns called Perc-O-Late Plus. Scotts company offers Lawn Builder and Wetting Agent, which also has fertilizer and a wetting agent.
Mowing: With warmer weather, a lawn won’t grow as fast as earlier in the season. It’s still important to mow regularly at the recommended height, which, for bluegrass (or mixes with bluegrass) lawns in our area, is 2 to 2.5 inches. It’s also important to mow using a sharp mower blade.
When you don’t mow often, you will “scalp” your lawn. Scalping is the result of removing more than one-third of the grass height. This injures the grass and causes it to use stored food reserves for new growth. Repeated scalping weakens grass, leading to thinning grass and invading weeds.
When a dull mower blade is used, it tends to shred the tips of the grass. If the blade is dull, the lawn probably will have a whitish cast to it. This is aesthetically unpleasing and damages the grass, making it susceptible to drought and disease.
Another cornerstone to keeping a lawn healthy is watering correctly and encouraging deep roots — but that’s a topic for another day.
-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.