KENNEWICK -- All summer, our lawns are subjected to stress from heat and stress from incorrectly watering, fertilizing and mowing.
By fall, lawns often are showing signs of accumulative stress, such as thinning grass, bare spots, weeds and poor color. Fall is a great time to relieve the stress and revitalize your lawn with its own special spa treatments.
First, provide your lawn with the essential nutrients it needs. Early September and again in November are the most important times of the year to fertilize.
During the fall when the weather turns cooler, lawns grow more dense with sideways growth. The last fertilization of the year is applied in early to mid-November when the grass has stopped growing and before the ground freezes.
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Next are some optional treatments, depending on what signs of stress your lawn is showing.
October is the best time of year to apply chemical control for perennial broadleaf weeds, such as dandelions, plantain, black medic and clover. Herbicides applied in October are very effective because that's when weeds are sending nutrients to their roots for winter storage. The herbicides are taken up by the plants and sent down to the roots along with the nutrients.
Of course, an herbicide applied to your entire lawn isn't needed if you only have a weed here and there. These are best dug out or spot treated.
Grassy weeds won't be controlled by broadleaf herbicides. However, now is a good time to note if you have an infestation of crabgrass. It goes to seed late in the season and can be seen sprawling in the lawn at this time of year. After hard frost it will virtually disappear, coming back from seed next year.
A significant amount of crabgrass means the fall spa treatments designed to make your lawn thick and healthy are especially important, since crabgrass needs light and space to germinate and grow. It also lets you know you may want to consider applying a crabgrass preventer herbicide in the spring.
Compacted soil makes it hard for air, water and nutrients to reach grass roots. When growing in compacted soil, grass roots tend to grow near the soil surface, making the lawn more vulnerable to stress from heat and drought. Grass with shallow roots also tends to develop thatch problems. Fall is a great time to aerate a lawn with a hollow-tined aerator. This must be done when the soil is moist; otherwise, the tines have no chance of penetrating compacted soil.
Aerating equipment can be rented at many equipment rental stores, or you'll often find businesses in the area who provide aerating services. The aerating process will leave plugs of soil and grass on top of you lawn. Leave the plugs on the lawn and they'll disappear with mowing. If your soil is heavily compacted, you may want to aerate again in the spring. Note: Even sandy soil can become compacted.
Giving a your lawn a little TLC now will mean a healthier, better-looking lawn next spring and summer.
Lawn note: Many different mushrooms have been popping up in lawns and landscapes around the area. This often happens when conditions turn cool and moist. Mushrooms are the reproductive structures of fungi that are decomposing organic matter in the soil. The organic matter can be dead tree roots, lumber scraps or thatch in a lawn.
The fungi don't hurt the lawn and are considered beneficial because they break down the organic matter. However, the mushrooms should be considered poisonous to animals and people if ingested. If they cause you concern, just pick or rake them out of the lawn and dispose of them. There is no chemical control available. Removal of the rotting organic matter is the only way to prevent the formation of the mushrooms.
* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension Office.