How to Get Rid of Crabgrass in 5 Steps

1. What is Crabgrass?

Crabgrasses (Digitaria spp.) are low-growing, summer annual plants spread by seed and from rooting nodes on top of the soil. Undisturbed, it can grow to 2 feet tall. Typically, crabgrass germinates in the spring when soil temperatures reach 55°F for several consecutive days. Crabgrass spreads all summer long and then produces seeds in the fall. 

Crabgrass thrives in poor lawns, edges of lawn areas where soil meets the pavement, bare spots, and neglected areas. Think of crabgrass as nature’s red flag!

What Does Crabgrass Look Like?

Once crabgrass seeds germinate, they begin the stages of leaf growth, starting with one leaf. When young, crabgrass looks like a small corn plant with blades that angle out from the stem. 

Mature crabgrass has a star pattern. After the crabgrass has grown to the fourth or fifth stage of leaf growth, it begins to “tiller” or branch off of the leaves

All of the stems radiate from a single root in the center of the plant but spread along the ground with “crablike” growth. Along the prostrate stems are nodes from which roots develop. (If you pull out “crabgrass” and find long taproots, that’s a different weed!)

By fall, the plant produces seed heads with spikes from the top of the stem. Each plant can produce thousands of seeds that remain viable in the soil for several years, so we say that this “annual” is a “perennial” problem.

2. Weed by Hand

If you have limited issues with crabgrass, you can easily hand-pull the plant when it’s young, thanks to its shallow root system. Crabgrass can’t regrow if you pull up the plant’s entire crown (basal growing point). Just water the area first to soften the soil and—to make removal even easier—use an upright weeding device.

As plants mature and the central taproot develops, removing the entire growing point becomes more difficult. Still, we do not recommend excessive tilling, as this will often bring up even more crabgrass seeds to the surface.

3. Use the Right Herbicide

When it comes to crabgrass, you either a) prevent it before it germinates or b) deal with it after it’s emerged. Your timing will affect what you do next. 

a) BEFORE crabgrass emerges: Obviously, it is best to prevent crabgrass before it germinates. This means “pre-emergent” herbicide spray.

If you read this article AFTER crabgrass has emerged, you should still address prevention next year. The most effective pre-emergent programs involve split applications: (1) Apply several weeks before expected crabgrass germination (often in April, in many regions) and then (2) make a second application 2 months later.

b) AFTER crabgrass appears: “Post-emergent” herbicides are the solution once crabgrass has already started to grow. This was a considerable challenge because many of the older post-emergent herbicides were ineffective and unsafe. Today, however, effective solutions can be sprayed directly on the crabgrass leaves WITHOUT harming your lawn.

For those interested, here is one of the best ready-to-use crabgrass post-emergents, made by Gordon’s®. It kills crabgrass and 200 other weeds (such as Canadian Thistle and foxtail) without harming your lawn. It also comes ready to use with a trigger sprayer formulation to spray directly on the weeds. Once the spray is dry, both people and pets can safely and immediately re-enter the areas. 

The Importance of Timing With Sprays

a) Using a pre-emergent herbicide can be tricky. Doing so not only requires planning but also very careful timing. It has to be applied BEFORE the seeds germinate at 55°F. How will you predict germination timing? Monitor soil temperatures and rely on your experience and phenological keys (e.g., when the forsythia bush flowers). Most garden centers sell inexpensive soil thermometers that you can use to zero in on the right timing.

b) Because of this challenge, it’s essential to be on top of post-emergent herbicide applications so that you tackle that crabgrass when it’s small!

1. Do not delay spraying a post-emergent spray—it’s most effective when the weeds are immature and actively growing.
2. This may require scouting for weeds. Just make it part of your daily walk around your yard and garden!
3. Addressing this issue well before planting seeds is essential, or you’ll have an even bigger problem the following year.
4. Use the right amount for the space to be effective. For example, with the Gordon’s® post-emergent crabgrass killer, you measure your lawn area to be sprayed. Measure length x width for square footage. Then, mix just 2.5 fluid ounces with 1 gallon of water for every 400 square feet of lawn. Apply to crabgrass with the ready-to-use spray bottle or in a spray pump or hose-end sprayer.
5. Using the same pre-emergents over and over can make crabgrass more resistant, so it’s vital to tackle this problem with post-emergent herbicides to maximize herbicide efficacy and manage against resistance that will grow over time.

4. Prevent Seed Heads

Do not let the weeds grow seed heads! New seeds produced by weeds go into the soil, eventually leading to more weeds. Imagine the thousands of seeds waiting on your lawn for next year!

1. Certainly, mowing will help reduce crabgrass growth, but remember that prostrate crabgrass tends to hug the ground and can still set seed when it’s as short as a 1/2 inch tall.
2. A post-emergent herbicide is the best way to finish off those crabgrass weeds.

5. Grow Healthy Turf

Crabgrass loves a poor lawn. So, the best protective step for managing crabgrass is a healthy, actively growing turfgrass. Always use best cultural practices (i.e., mowing, fertilization, irrigation). Because seedling crabgrass isn’t very competitive, a healthier lawn will crowd out new seedlings.   

1. Select turfgrass adapted to your location. So many people don’t choose the right grass for their conditions! Regarding beating out crabgrass, perennial ryegrass is the best competitor. It also provides some natural insect control, emitting a natural poison that gives some small, damaging bugs the “flu.” Ask your garden center about ryegrass or what works best in your climate.
2. Feed your soil to get turfgrass off to a strong start! Supply nitrogen in early autumn and, if needed, in spring, when cool-season grasses are more competitive than these warm-season weeds. Again, speak to your local garden center.
3. Mow at the highest height recommended! Mowing too low allows more light into your lawn grass, which aids more crabgrass germination. Mowing high won’t get all crabgrass, but research shows that doing so works significantly better than a low mowing height to reduce crabgrass infestations.
4. Water the correct way! Light, frequent sprinkling only encourages crabgrass, which has shallow roots. Real turfgrass needs deep, infrequent irrigation to reach its roots. The ideal solution is an irrigation system that waters only when you notice that the grass seems dry. If you mow tall, you may not even need to water turfgrass in the spring, provided you get an inch of weekly rainfall.

With the major five steps above, you can take control of crabgrass. By following good cultural practices (such as mowing high), regularly scouting for young weeds, and using an effective post-emergent herbicide, you’ll break the cycle and prevent the spread of crabgrass!