Gardening with Allen: Weedy grasses need treatment

Large areas of my lawn have ugly coarse and/or off color grass I call it crab grass. I have tried digging it up, but it comes right back. Is there any way I can get rid of this grass without completely replanting my lawn?

There are a number of wild grasses which invade lawns in our area, but crab grass is not one of them. It is too cool for crab grass to develop in our area. However some of the other grasses are much worse than crab grass.

The reason they come right back after you dig them up is that they have underground rhizomes that resprout unless the total root system is removed. Roundup and other weed control products which contain glyphosate will kill these grasses including the root system, but sometimes more than one application is needed. However, Roundup will also kill any lawn grass which it touches.

Roundup has introduced a new product which is a gel in a pencil-like applicator. These off-type grasses usually grow faster than regular grasses such as ryegrass so they are taller a few days after mowing. At that time the tips of the coarse grass leaves can be touched with the gel without touching the desirable grass.

Check a week or two after treating to make sure the coarse grass is dead. If any green is showing re-treat. You can cover the dead grass with some soil or soil mix from a nursery and plant lawn grass seed into the soil. Rake the soil so that most of the grass seed is covered. There is no need to remove the dead coarse grass since it will decompose and become part of the soil.

Trees often have grass growing right up to their trunk. When this grass is trimmed with a line trimmer, it damages the bark and can stunt young trees. This grass can be killed by spraying or with the gel and can also be covered with soil.

Where major lawn areas are deteriorated by weed growth or other conditions such as insect or disease damage, I have sprayed the entire lawn and top dressed with enough soil to just barely cover the dead grass and weeds and then planted grass seed into this soil topdressing.

Any time grass seed is planted fertilizer should also be applied. It is critical to irrigate lightly and frequently enough so that the top of the soil stays constantly moist for 3 to 5 weeks until seed has sprouted. This may mean 5 or more times a day for a brief 2 to 5 minutes.

Allen Wilson is a Vancouver gardening specialist. Email Allen Wilson at allenw98663@yahoo.com.

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