How to Identify Crabgrass

If you have a lawn, there is a good chance you have crabgrass, too. To make matters worse, there are two main types: large crabgrass and smooth crabgrass. Both types of crabgrass are annual weeds that emerge in warm weather and die at the first frost. Eliminating crabgrass from the lawn can be troublesome, but identifying the weed is the first step towards a lush, healthy lawn.

Difficulty: Moderately Easy

Instructions

1. Determine that the plant is a weed. A weed is considered to be any undesirable plant in your lawn or garden. It may or may not be unattractive. Everyone involved with the maintenance of turfgrass will agree that crabgrass is a weed.

2. Observe the weed's general appearance. Both large and smooth crabgrass can grow upright or prostrate, forming the familiar "crab-like" shape, and have many branches. Large crabgrass has more of a tendency to form a mat and can grow to a height of 3 feet. Smooth crabgrass is smaller usually reaching no more than 15 inches in height. Large crabgrass can sometimes be identified by its purple stems.

3. Examine the leaves of the weed. Large crabgrass leaves are usually pale blue green in color while smooth crabgrass is normally a dull green. The leaves of both types of crabgrass are rough on the margins and sharply pointed. Large crabgrass leaves can be 2 to 6 inches long while smooth crabgrass reaches approximately 4 inches in length. Both have leaves 1/4 inch wide.

4. Note the weed's location. Crabgrass will grow in moist, warm areas of a lawn that is thin or has been mowed too short. Both forms of crabgrass can also be found crowding out desirable turfgrass in compacted, dry areas of the lawn.

Tips & Warnings

• Your local library or book store will have many garden reference books that should also help in identifying weeds.
• Maintaining a thick, healthy lawn mowed to a height of no less than 2 inches is the best preventative for crabgrass.
• If you have any doubts on the identity of your weed sample, take a sample to your local nursery, county extension office or garden center for confirmation.