How to Kill Crabgrass in Lawns

Crabgrass is universally hated by anyone who wants a nice lawn. The best ways to kill crabgrass in lawns are with chemicals and practicing proper lawn maintenance.

Description of Crabgrass

Crabgrass has coarse, light green leaves on heavy, thick stems that form a compact circle at ground level.

Crabgrass multiplies by stems rooting at the lower nodes and by seeds. The seeds dropped the previous fall sprout to form new plants in the late spring to early summer. It grows fast until the purplish, seed head forms in summer or early fall.

Control of Crabgrass

Crabgrass requires high light-intensity. Once established, it is very hardy. It will tolerate high temperatures, compacted soils, and dry soils better than most turf grasses.

Although crabgrass can appear throughout your lawn, it is most commonly found along cobblestone, asphalt driveways, and sidewalks. These areas are hot zones because stone and concrete heat up rapidly in the summer sun.

Crabgrass can be controlled with pre-emergent herbicide, post-emergent herbicide, and with proper lawn maintenance.

1. Pre-Emergent Herbicide

Preemergent weed control must be applied in the spring before seedlings appear. The best timing is usually when forsynthias finish flowering in late April.

Herbicides that work best contain benefin, bensulide, DCPA, oxadiazon, pendimethalin, or siduron.

Note: Don't expect the use of pre-emergent herbicides to be a foolproof method. Every summer, I still need to use a post emergent to deal with crabgrass.

2. Post Emergent Herbicide

For postemergence control, use MSMA or MAMA. More than one application is often required.

If you get tired of trying to kill crabgrass in lawns or don’t want to be exposed to pesticides, have a local lawn treatment company do it. I like how you can sign up online for a free estimate.

3. Proper Lawn Maintenance

Since crabgrass thrives on patchy, sparse turf. So reduce the need to kill crabgrass in lawns with these lawn maintenance tips.

  1. Mow high and mow often. Mowing high means keeping your grass on the longer side of its optimal height. This keeps the soil cooler and provides shade that restricts the growth of annual weeds. Weed seeds on the soil surface need the heat of the sun to flourish. Scalping your lawn is an open invitation for weeds. Second, once weeds have already invaded your lawn, frequent mowing will keep them in check. A weed can't form seedheads when its topmost growth keeps getting lopped off.
  2. Fertilize at the correct times. The goal is to feed your lawn, not your weeds. Cool season grasses should be fertilized in early spring and late fall. Fertilizing cool season grasses in the heat of the summer will only promote more weeds. Warm season grasses should be fertilized at the height of their growth period in the summer. Avoid feeding in the cooler spring or summer when the weeds are likely to emerge.
  3. Water deeply and infrequently. There are weed seeds hiding out in your lawn just waiting for the right conditions to emerge. Those seeds grow best when kept damp with light frequent watering.
  4. Reseed in the Fall. The fall is the best time to reseed for several reasons. Grass has nine months to get its roots deep and to get more established before facing the summer heat. It has a better chance surviving than grass planted in the spring. In the North, crabgrass and other weeds complete their life cycles in the fall and die out. So they aren't there to compete with the new seedlings for space, water, and soil nutrients.

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