Mid Summer Weeds in the Lawn

Steve Allgeier
Carroll County Master Gardener Program

Many people are able to distinguish the weeds from the turf grass, but few are able to identify what type of weed they have and/or how to deal with it.

Weeds are opportunistic and tough. They take advantage of turf that is thin or poorly developed. These past couple summers have allowed weeds to develop because of thin stressed lawns. Therefore, the key to controlling weeds is prevention. In the lawn that means maintaining a dense, vigorous lawn (easier said than done).

The biggest lawn weed culprit has been Ground Ivy (Glechoma hederacea). This is a creeping low perennial that vines its way through thin grass, rooting as it goes along. The leaves are generally roundish with scalloped leaf margins. It typically creeps out from the shady moist protection of trees and shrubs and into the lawn. If you catch this weed early it can be routed out with hand pulling. If, however, you have too much to hand pull or the Ground Ivy has become too established, it is best sprayed in the fall with a weed killer containing triclopyr.

The other notorious weed this year has been Crabgrass (Digitaria). Again, like other weeds, this one takes advantage of thin lawns and is best prevented by maintaining vigorous dense turf. Crabgrass is a more common weed that almost everybody recognizes. This summer annual is a course spreading grass like plant that has a low habit and telltale seedhead consisting of a central stem with typically 3 5 thin umbrella "arms" of seeds at the top. Preemergent herbicides offer your best control if you have established Crabgrass. A preemergent is an herbicide that prevents weed seeds from germinating. The biggest problem most people find is that they have applied the preemergent to late for it to be effective. In our part of Maryland this is typically done when the Forsythia are in bloom, around the end of March or beginning of April.

Please remember that you cannot reseed your lawn while using a preemergent herbicide, it will also kill regular grass seed. Herbicides can be poisonous, but they may be used safely if you handle them with care. Use only the recommended rates. Read and follow the directions and precautions on the label.

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