Crabgrass: How To Get Rid Of This Weed For Good



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!

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What Is Crabgrass?

The Digitaria genus of grasses is widespread, with different individual crabgrass species around the world. Typically, they can be found in warm, temperate regions.

In the United States, the most common crabgrass plants are of the Digitaria sanguinalis species, 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. For a grass, it’s surprisingly protein-rich, and makes a reasonable animal fodder.

Digitaria ischaemum is another common species, and is commonly known as smooth crabgrass. Smooth crabgrass (much like hairy crabgrass) is also considered a noxious weed in many parts of the US. While smooth crabgrass and other varieties are different species, their removal techniques will be the same.

Identify smooth crabgrass by its broader and coarser blades.

Hairy crabgrass seeds easily by itself (and can produce up to 150,000 crabgrass 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 plants are raised as a grain crop for humans, with crabgrass seeds harvested throughout the summer months. These small crabgrass 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 broadleaf weeds thrive in temperate areas and are quite widespread.

Identifying Crabgrass

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, which is why they’re considered broadleaf weeds. 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 a crabgrass plant 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.

Each crabgrass plant 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, it can be difficult plant to control crabgrass or completely eliminate it. However, it can be done. Let’s go over the best solutions for crabgrass and how to keep it at bay.

Without Chemicals

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 before it becomes actively growing crabgrass. Since this grass will grow from prior seed once soil temperatures reach 55 degrees Fahrenheit, crabgrass seedlings 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 seedlings 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 to completely remove the weed seeds.

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 seed germination.

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 pre-emergent herbicides. Corn gluten meal is the most popular organic choice.

Available as a large 25-lb bag of granulated meal as 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 organic 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 subsequent crabgrass will begin to grow and produce seed.

If you have a shady spot in which grass has a hard time growing, 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!

With Chemicals

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 is a good solution in these cases. This pre-emergence crabgrass treatment is meant to be applied early in the spring, before soil temperatures get 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. This ensures you effectively control crabgrass and that you’re on your way to eliminating it.

In warmer climates, you’ll need to use pre-emergence treatment twice per year. Use it as soon as the soil temperatures reach 55 degrees in the early spring, and then in the fall to prevent winter weed growth. Once the soil temperatures dip 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. 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 hairy and smooth 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 seed 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 before the soil temperature gets too warm. The good grass seeds germinate and take over the lawn, and then you can simply remove any stray clumps of crabgrass that might appear.

Q: What will kill crabgrass but not grass?

A: A weed spot killer or cornmeal gluten should take care of crab grass and leave the rest of your grass alone.

Q: Should I remove crabgrass from my lawn?

A: Remove it as soon as you see it to prevent it from becoming a big problem in your lawn. It’s also a noxious weed that outcompetes other native lawn grass. Its removal helps support your local ecosystem.

Q: What is the fastest way to get rid of crabgrass?

A: Remove the seedlings as soon as they arise in early spring. Then overseed a native lawn grass. As the seeds of these native turfgrass species germinate, they’ll push out any potential young crabgrass.

Q: Is crabgrass a good grass?

A: In North America, crabgrasses are invasive broadleaf plants that prevent the thriving of native turfgrass species.

Q: Will crabgrass grow back if you pull it out?

A: It might, but if you seed generously with a native seed, that should prevent hairy and smooth crabgrass plants from returning. Do this all before the soil temperature gets above 55°F (13°C).

Q: How do you get rid of crabgrass permanently?

A: You’ll have to actively control crabgrass for more than one growing season. Try using a combination of the techniques listed above to keep regrowth of crabgrass seeds at a minimum.

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