- 1 What Is Crabgrass?
- 2 Identifying Crabgrass
- 3 How To Get Rid Of Crabgrass
- 4 Frequently Asked Questions
Crabgrass can invade and conquer your lawn if you give it a chance. Little tufts of quick-growing wild grasses can create trip hazards, and it’ll spread like wildfire wherever there’s any open space. So what’s the best way to get rid of crabgrass? Is there a good crabgrass treatment?
Today, I’ll tell you everything that I know about this annoying weed. If you’ve been asking how to get rid of crabgrass in your yard, this piece is meant for you. It may take some time, but you can have a crabgrass-free lawn!
Listen to this post on the Epic Gardening Podcast
Good Products To Kill Crabgrass
- Espoma Organic Weed Preventer
- Agralawn Crabgrass Killer
- Scotts Halts Crabgrass & Grassy Weed Preventer
- Bonide Weed Beater Plus
What Is Crabgrass?
The Digitaria genus of grasses is widespread, with different individual Digitaria species around the world. Typically, they can be found in warm, temperate regions.
In the United States, the most common crabgrass variety is Digitaria sanguinalis, also known as large crabgrass, hairy crabgrass, purple crabgrass, and a few other names.
Digitaria sanguinalis was originally not native to the United States, but was brought here as a forage crop by immigrants. For a grass, it’s surprisingly protein-rich, and makes a reasonable animal fodder.
Crabgrass self-seeds easily (and can produce up to 150,000 seeds per plant during its growing season!), and has become an invasive grass in most temperate states. It’s adapting to cooler climates as well. Commonly seen springing up on lawns, it also forms in pavement cracks or planters. And it can be hard to kill.
Some crabgrass is raised as a grain crop for humans, with seeds harvested throughout the summer months. These small seeds are highly nutritious. Both Digitaria sanguinalis and others, including Digitaria compacta (commonly called raishan), Digitaria iburua (black fonio) and Digitaria exilis (white fonio) are grown as food crops.
For now, we’re going to focus primarily on Digitaria sanguinalis, simply because that’s by and large the most common weed variant in the United States and is found abroad as well. But Digitaria is quite widespread.
Take a close look at your lawn. Is it made up of nice, straight, single grass blades, or does it seem to all be connected? The connected grasses are often crabgrass, and that’s a major problem.
Generally, most crabgrass varieties found in the United States grow in a round clump. Sometimes these are ragged clumps, and in other situations they’re quite full and broad. In fact, that’s how it got the name crabgrass — the clumps resemble a crab’s shell, with occasional extensions in lieu of the arms.
When you discover it in your lawn, you’ll readily be able to identify this persistent plant, especially Digitaria sanguinalis. There’s a central point from which stems and leaves grow in all directions, often with tall seed stalks from its center.
Most of the time it will be sprawled on the ground, although there are some varieties (such as Digitaria cognata, the Carolina crabgrass) which can grow upright.
Digitaria sanguinalis forms a very dense mat that can mature to be a really thick clump about 2-3″ tall. The more established the grass is, the more likely it’ll spread. Remove this before it can seed.
Crabgrass also provides its own “mulch”, as dead portions of the plant will act as a self-sustaining mulch beneath the live portions. This means it can protect its moisture supply and continue to grow.
If you have bare patches of ground, you may find this plant appearing on its own. It’s quite opportunistic, and will take any available space it can get!
How To Get Rid Of Crabgrass
Due to its tendency to regenerate if the roots remain in the soil, this can be a difficult plant to completely eliminate. However, it can be done. Let’s go over the best solutions for crabgrass and how to keep it at bay.
Knowing when to kill crabgrass is almost as important as how to kill it.
Ideally, it’s best to kill crabgrass in spring, as early as you can. Since this grass will grow from prior seed once the soil temperature reaches 55 degrees Fahrenheit, young patches will appear in the late winter and early spring months. This is when the plant is easiest to remove, because its roots will not be as deep and it can easily be dug out by hand.
Removing crabgrass should be quickly followed by re-seeding of your intended lawn. The quicker you can get the dead patches filled in by healthy lawn growth, the less likely that your crabgrass will return!
Seed with lawn grasses that grow naturally in your area. You can occasionally use a lawn “patching” product that provides quick-growing grass to fill in lawn holes. Some patching products may contain grass varieties that aren’t native to your region, so be careful to get the right kind. Most local stores carry products appropriate for that region.
As much as I hate to say it, the best way to eliminate crabgrass is to get it out, roots and all. The more you can remove before it produces seed, the less likely it is to reappear. However, crabgrass seeds can remain in the soil up to three years, so this is a long-term project and requires some dedication.
Be vigilant along edges of sidewalks, driveways, and walkways. As concrete or blacktop surfaces heat up quicker in the early part of the year, they provide a great location for early crab grass growth.
Use a good lawn edger and provide a slight gap between paved surfaces and turf to knock back weed growth.
Organic Crabgrass Solutions
Once you have gone through the backbreaking effort to remove crabgrass by hand, you can use a pre-emergence weed inhibitor product. Corn gluten meal is the most popular organic choice.
Available as a large 25-lb bag of granulated meal as Espoma Organic Weed Preventer, this cornstarch byproduct will slow or completely stop the growth of most weeds such as crabgrass and dandelions.
However, you’ll need quite a bit of corn gluten meal. A 25-lb bag will cover 1250 square feet, and you’ll need to use it in both spring and fall to prevent weed growth.
Trying to find out how to get rid of crabgrass in the summer? It’s already probably there. You’ll need to use some form of crabgrass spot treatment.
One good option is Agralawn Crabgrass Killer, a powder made mostly of cinnamon bark and corn gluten meal. Wet the crabgrass and sprinkle this on, thoroughly coating the grass clump. This post-emergence crabgrass treatment will kill off the weeds without impacting your lawn grass.
Make sure that your lawn stays thick, avoid bare spots that could develop crabgrass, and cut your lawn at the right height for your grass variety. For most typical lawn grasses, the appropriate height is 2-3 inches. If you maintain it at that height and keep it regularly mowed, it’s unlikely that more crabgrass will grow.
If you’ve a shady spot which grass has a hard time growing in, consider removing the grass in that area and replacing it with mulch or stone chips with landscape fabric underneath. This reduces watering needs, and it can be a visually-appealing addition to your yard. And you don’t have to mow it!
I don’t like using chemical alternatives. But if crabgrass has infested most of your lawn, you may not have a choice. You can go through and remove the top layer of your lawn and reseed, but will that get all the roots? Can you keep it from returning long enough to get your new lawn thick enough to repel weeds?
Pendimethalin weed preventer, such as Scotts Halts Crabgrass & Grassy Weed Preventer, is a good solution in these cases. This pre-emergence crabgrass treatment is meant to be applied early in the spring, before soil temperature gets above 55 degrees.
Don’t seed, rake, or aerate your lawn for four months after application to make sure that the weed preventer does its job.
In warmer climates, you’ll need to use pre-emergence treatment twice per year. Use it as soon as the soil temperature reaches 55 degrees in the early spring, and then in the fall to prevent winter weed growth. Once the soil temperature dips below 50 degrees consistently, pendimethalin treatments are less effective.
If you just have a persistent clump that won’t die by any other means, opt for a crabgrass spot treatment like Bonide Weed Beater Plus. Spot treatments will typically eliminate reappearing plants with ease.
You can use more volatile chemicals if you want, but I prefer products that will eventually go inert, which Bonide’s formula does. Only use it where you absolutely need it!
Frequently Asked Questions
Q: Does crabgrass die in the winter?
A: Well-established crabgrass has tolerance to light frost, but generally won’t take constant frost-and-thaw cycles. It won’t survive hard frosts and freezes. If you live in the southern half of the US, it might survive year-round. Northern dwellers will see their crabgrass die off during cold months, making use of pre-treatments easier.
Q: Can you plant grass seed with crabgrass preventer?
A: Since most preventative crabgrass treatments reduce germination, it’s not recommended. Wait four months at the minimum before reseeding. If that puts you in the hot summer months, wait until late summer or early fall to seed again.
You can overseed to repel crabgrass, too. In the fall or the early spring, heavily seed the area instead of using preventer. The good grass will take over the lawn, and then you can simply remove any stray clumps of crabgrass that might appear.
Ready to conquer the crabgrass now? I know I am. In fact, I’m going to go dig a persistent clump out of the yard as soon as I finish writing this! Do you have any preferred solutions for your crabgrass growth? Share your tips in the comments below.