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In garden areas, pull or dig out crabgrass plants before they set seed. In the lawn, raise the height of your mower to shade out crabgrass seeds and seedlings.
Other Common Names
Several crabgrass species are lawn pests. Large, or hairy, crabgrass (Digitaria sanguinalis) has a thick, hairless stem that can be upright or spread on the ground. The leave blades are usually hairy and 1/4-1/3 inch (6-8 mm) wide. The sheaths that surround the stem have a dense covering of long hairs. The flower head is a whorl of three to ten finger-like spikes at the top of the stem. Smooth crabgrass (D. ischaemum) is less coarse and shorter than large crabgrass.It also has a purple tinge and is much less hairy. The flower head has two to six spikes.
Large crabgrass can grow to 3 feet (90 cm) tall; smooth crabgrass can reach 15 inches (40 cm) tall. In lawns, both species can adapt to whatever mowing height you use.
Preferred Site and Climate
Crabgrasses are most common in dry, sandy soil, but they tolerate a range of conditions in lawns, gardens, and neglected areas. Although both species are found throughout the United States, large crabgrass is not in North Dakota and portions of adjacent states, and smooth crabgrass is not in southern Florida, west Texas, and most of New Mexico and Arizona.
How it Spreads
By seed. Prostrate plants can also root at the stem nodes.
Pull or dig up plants before they set seed. Raising the height of your lawn mower (to the opper range that your grass can tolerate) and fertilizing the lawn will help the good grass crowd out this weed. Apply corn gluten meal over the lawn in late spring can kill existing seeds as they sprout.
Repeated mowing encourages plants to grow in a spreading form, so mowing by itself will not control the plants or prevent reseeding.