Recommended Treatment of Crabgrass

High Mowing Height

• Most lawnmowers have the ability to cut grass to a certain height by raising or lowering the blades. If you notice crabgrass beginning to get a foothold in your lawn, look up the proper growing height of the grass that you have in the yard. Set the mowing height to that level. A high mowing height allows the grass in your yard to stay healthier, and it also allows the mature grass to shade the crabgrass seedlings. Shaded crabgrass seedlings are sickly and are less likely to mature into healthy, seed-producing adult plants.

Pre-Emergence Herbicides

• While crabgrass is persistent, it is short-lived. It is possible to treat the following year's crabgrass with pre-emergent herbicides during the late fall or the early spring. Prodiamine is an herbicide you can use on any established turf, though you should not use it during the first 60 days of a newly seeded or overly seeded lawn. Dithiopyr is another pre-emergent herbicide marked for used for fine fescue, perennial ryegrass, Zoysia grass, creeping bentgrass and Kentucky bluegrass.

Post-Emergence Herbicides

• Post-emergence herbicides take care of crabgrass after it becomes established in the lawn. According to Pennsylvania State University, methanearsonate, fenoxaprop-ethyl and quinclorac are all suited for this purpose. While these herbicides are effective, they tend to affect the grass around them as well. When applying a post-emergent herbicide, look closely to see whether you can use it on the turf grass that you have in your lawn. Apply it while the crabgrass is still young and soft.

Deep Watering

• Deep watering involves soaking the soil to a depth of 4 to 6 inches every few days. This is the equivalent of between ½ inch and 1 inch of rainfall. Crabgrass thrives in a drier environment, and a damper environment allows your turf grass to root more strongly to the soil, allowing them to out-compete the crab grass. To figure out how much you are watering your lawn, leave a can near the sprinkler and see how much it fills up as you water.