What is Crab Grass?

Mary McMahon
Mary McMahon

Crab grass is a grass in the genus Digitaria, native to the temperate zones of Europe and Asia. Grasses in this genus are also sometimes referred to as “finger grasses,” in a reference to the long stalks they produce during summer and fall flowering and seed production. In many regions of the word, crab grass is regarded as a noxious weed, because it is invasive, and will take over readily, choking out other plant species.

Crab grass can overtake nearby plants species very quickly if left to grow.
Crab grass can overtake nearby plants species very quickly if left to grow.

In particular, crab grass is viewed as the scourge of gardens the world over. Particularly in lawns, crab grass can wreak a great deal of havoc, replacing cultivated lawns with the less attractive bladed leaves of crab grass. The grass spreads very quickly, making it difficult for gardeners to control.

The habits of crab grass are actually not terribly unusual for grasses. Many grasses have adapted matted growth habits similar to that of crab grass so that they can choke out their competition, ensuring that they have access to as much water, sunlight, and soil nutrition as possible. The matted growth also allows the grass to put out adventitious shoots which can develop into new plants, making reseeding less necessary.

When crab grass is introduced, it can be particularly irritating, as it may choke out native species which are not prepared to defend themselves against crab grass. Especially in delicate ecosystems, crab grass can become a very serious problem.

There are two ways to control crab grass: herbicides, and natural approaches. Herbicides can be used to treat a lawn to prevent the growth of crab grass, and to kill shoots if they get a chance to arise. However, using herbicides can be tricky, as the chemicals can damage other plants in the lawn, and also potentially pollute the surrounding area if they filter down into the water table or run off into streams.

Natural approaches to crab grass control include mowing high, which allows desirable grasses to shade the ground, making it difficult for crab grass to grow, and watering deeply and infrequently. Crab grass has shallow roots, so it prefers frequent shallow waterings, and may die off otherwise. Using native plant species in the garden can reduce the need for water, making it easier to eliminate crab grass. Crab grass can also be controlled by hand, by picking crab grass as it appears. With persistence, this method can pay off, assuming the neighbors don't have a yard full of crab grass which can reseed yours.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

You might also Like

Readers Also Love

Discussion Comments


I take the approach that natural is the best way to go. Using crab grass killers purchased at the store may be easier, but why use these poisons when you don't have to. This article makes a good point about controlling the grass by simply using a particular watering technique. How easy is that?

Also, if you have only a few weeds in your yard, you can dig them up as they appear and this will keep them under control. If you do have to use some type of weed killer then at least choose a spray that you can apply directly to the individual plants, so you don't have to put poison over the entire lawn and increase the risk that the harmful chemicals will filter into drinking water.


The article explains the options that can be used to kill crab grass. Given a choice, I will go for a herbicide fertilizer mix that I can simply spread over my entire lawn. This way I can get rid of the harmful crab grass and other weeds while feeding the grass I do want.

I have tried various brands of these weed kill plus fertilizer products, and they all worked about the same. I have yet to find one that takes care of all the crab grass with one application, and even when you think you have gotten rid of all the crab grass a few plants will pop up from time to time, so you just have to stick with the applications.


I've been trying to get my lawn into decent shape this season. I'm not a fanatic about the way my lawn looks. However, I want the yard to look decent. The biggest issues we have are weeds and clean spots where grass has died. There is one weed in particular that I have been battling, and I can't say that I am winning the battle.

Until recently, I had no idea what this invader was. My neighbor told be it is crab grass, and pretty much impossible to get rid of. He says he has it all over his lawn, and he just tries to keep it under control so it doesn't take over the entire lawn.

Post your comments
Forgot password?