If you want to get rid of crabgrass, you’ll need to attack this pervasive weed from many angles. You can treat existing crabgrass using conventional and organic methods such as manual removal, applying vinegar, and depriving plants of sun and air. Then, you can implement lawn care techniques like using pre-emergents, mowing at the right height, and watering wisely to help prevent future problems.
Over time, employing a myriad of these techniques will help reduce crabgrass in your lawn.
What is crabgrass?
Crabgrass is a tenacious annual weed that thrives in hot weather. It typically appears in light green to yellowish-green shades, and the coarse-textured leaves are wider than traditional turfgrass blades. The leaves are covered in tiny hairs, and the round stems are often reddish-purple.
You often see crabgrass growing in low-to-the-ground clumps instead of spreading across your lawn. As it grows, it produces branches or tillers from the center that resemble crab legs, hence its name.
As an annual summer weed, crabgrass germinates in spring, matures during the warm season, and dies after the first frost. Unfortunately, this doesn’t mean you only see it in your lawn for a season. When left to go to seed, each crabgrass plant produces around 150,000 seeds that will lie dormant until temperatures warm up again next spring. Then, the process begins again.
Crabgrass favors thin turf or turf with areas of bare soil. It is also common to see it growing along sidewalks. The soil along paved areas tends to be shallow, thin, or of poor quality, which invites crabgrass to grow.
Treating existing crabgrass in your lawn
Chances are, if you are still reading this article, you’re dealing with a crabgrass invasion of your lawn. If that’s the case and you are trying to get rid of it as quickly as possible, here are some of the most tried and true weed control methods.
Remove crabgrass by hand
If crabgrass is only growing in a small area, hand weeding is one of the most effective, albeit labor-intensive, eradication methods. Securely grasp the above-ground part and use a screwdriver or weed puller to remove the crabgrass plant and its roots from the soil. It’s essential to try and get as much of the roots as possible.
Then, put the weeds in a trash bag so the seeds can’t settle back into the lawn.
Use vinegar as a natural herbicide
Vinegar has gained significant popularity as a natural and environmentally friendly herbicide. When sprayed directly onto plants’ leaves and stems, the acetic acid in vinegar desiccates and burns the tissue(s), leading to their eventual death.
For the best results, spray crabgrass seedlings on a warm, sunny day within two weeks of germination. One application may be sufficient for very young plants, but you may need to apply two or three times for slightly older crabgrass.
Before you grab the vinegar bottle from your pantry to tackle crabgrass in your yard, you need to know a few things. Household vinegar (5% acetic acid) may be effective for very young crabgrass, but if you want a higher success rate, consider a horticultural vinegar with 20% acetic acid.
Vinegar is also nonselective, damaging any plant tissue it comes in contact with. So, spray accurately for the best results.
A note on safety: Homeowners are advised that even “natural” products can pose safety hazards if not used per the manufacturer’s instructions. Acetic acid at high concentrations can burn the skin or eyes, causing permanent damage or even blindness. Always follow the instructions on the label for safety and maximum effectiveness.
Try steam cleaning
Steam and boiling water also can be effective in fighting crabgrass. The heat cooks the plants by disrupting their cellular structure.
Large organizations use commercial steam equipment to accomplish this task, but homeowners usually boil the water in a tea kettle or pot. Once hot, pour the boiling water over the weed, wait a week until it is brown, and then remove the plant by hand.
As with most non-chemical methods, repeated applications are typically needed for the best results. This method is also nonselective and will kill any plant tissue it contacts.
Reach for organic herbicide products
Organic weed killers are a good option if you’re looking for a more natural approach to removing crabgrass. It is important to note that the retail market offers relatively few organic options compared to conventional herbicides like glyphosate and 2-4, D. This limited selection is because considerably fewer naturally occurring chemicals do an excellent job of killing weeds.
Most organic herbicides contain active ingredients that remove the waxy cuticle on plant leaves or damage cell walls, causing desiccation (loss of moisture) and senescence (loss of the ability to divide and grow).
Active ingredients in organic products include:
- Herbicidal soaps containing long-chain fatty acids such as capric or caprylic acid or ammonium nonanoate
- Vinegar or acetic acid
- Citric acid
- D-limonene, a common terpene found naturally in citrus peels such as orange, lemon, grapefruit, lime, and mandarin
- Essential oils such as clove, cinnamon, summer savory, and red thyme
Note: If you are looking for a product approved for organic production, look for the OMRI label.
Use a conventional, post-emergent weed killer
Store-bought herbicides are often considered an easy, convenient method of control for existing weeds or weeds that pop up during the growing season. In addition to the well-known glyphosate, conventional, post-emergent crabgrass killers contain many other active ingredients. Many are specifically marketed on the product label as crabgrass treatment or prevention.
Some products only target broadleaf weeds like dandelions, so be sure your product is effective on grassy weeds, including crabgrass.
When applying lawn chemicals:
- Always read and strictly follow the manufacturer’s instructions and safety guidelines on the herbicide label. Pay attention to recommended application rates, mixing instructions, and safety precautions.
- Wear appropriate personal protective equipment (PPE) such as gloves, safety glasses, long sleeves, long pants, and closed-toe shoes to prevent contact with any product.
- Apply herbicides on calm days to minimize drift onto non-target plants, water bodies, or neighboring properties.
Smother the crabgrass
Lastly, if you have a large patch of crabgrass to get rid of, you can try to smother it, depriving it of sunlight and oxygen.
Cover the crabgrass with large garbage bags or black plastic sheeting, securing the corners with bricks or landscaping pins (sometimes called stakes) so the covering stays in place. After a couple of weeks, everything under the plastic should be smothered out and dead.
If you take this approach, take that last sentence to heart. Everything under the plastic should die. So, if you smother your lawn, you’ll also kill the turfgrass.
Preventing crabgrass in the future
To prevent crabgrass in the future, consider pre-emergents and follow a few common-sense maintenance practices. A healthy lawn prevents weeds by providing competition and depriving the crabgrass of light and space.
Follow these essential lawn care maintenance tips to increase your lawn’s health and decrease the crabgrass.
Stop crabgrass from emerging
One of the best ways to be proactive with crabgrass is to apply a pre-emergent herbicide that prevents it from taking root in your lawn. Pre-emergent herbicides (also called weed preventers) are used before plants start growing. They create a barrier in the soil and kill a plant’s roots and shoots, preventing them from emerging through the soil surface.
Application timing is critical when using pre-emergent products. Crabgrass seeds emerge in early spring when the soil temperature reaches 55 degrees Fahrenheit for several days in a row. To stay ahead of seed germination, late winter or early spring is usually the best time to apply pre-emergents.
For exact information on when to apply pre-emergent herbicides in your area, contact your local Extension Service.
When choosing a pre-emergent, look for a product formulated for grassy weeds, including crabgrass. Some pre-emergents are selective, which means they work only on broadleaf or grassy weeds; some are non-selective and work on all weed types.
Numerous types of pre-emergents are available at your local home improvement store, ranging from convention and organic options to liquid and granular products. Corn gluten meal is a popular non-chemical pre-emergent, though experts are divided on its efficacy.
Most products can be used anywhere on the lawn or in flower beds. Granular products are popular, and they should be applied using a spreader and then watered into the soil. This is general guidance; check the label on your product for specific instructions.
Pro tip: For help picking out a product, check out Lawn Love’s guide on the “6 Best Pre-Emergent Herbicides of 2024.”
Mow your lawn the right way
Mow at the upper range of recommended mowing heights for your grass type. The idea is that a tall lawn will keep the soil floor shaded, which means the crabgrass will not have the light it needs to grow. Crabgrass will not tolerate shade, so keeping the grass tall lets the grass do some of the preventive work for you.
When it is time to mow, follow the one-third rule. The one-third mowing rule — which advises against cutting more than one-third of the grass blade height — is a widely recommended lawn care tip to keep grass healthy and thriving. It helps reduce stress on your lawn and allows it to recover more quickly after mowing.
When your lawn is healthy, it can better out-compete weeds like crabgrass for resources like water and nutrients. On the other hand, when your lawn is stressed, it’s easy for weeds to come in and gain a stronghold.
Finally, if your crabgrass has already gone to seed, bag your grass clippings and dispose of them in the trash. If you leave the clippings on the ground, you will be re-seeding a new generation of crabgrass on your lawn!
Water wisely
Water deeply and infrequently to encourage the lawn’s roots to grow deeper into the soil. A deeper root system helps improve the grass’ drought tolerance and keeps it healthy and strong.
Whether you water by hand or rely on your sprinkler system, aim for about 1 to 1.5 inches of water per week. Break this up into two or three watering sessions.
How long you water your lawn depends on your sprinkler system’s output. You can perform a tuna can test to help determine how long it takes to put down an inch of water.
Also take into account any rainfall that week.
Dethatch and aerate
Soil compaction can happen all too easily in a home lawn. When it does, it inhibits the movement of air, water, and fertilizer into the soil, contributing to a thin turf and a weed-friendly environment. Dethatching and aeration are necessary lawn maintenance chores to keep soil compaction minimal.
- Dethatching removes the thatch layer from the lawn, clearing away the living and decomposing stems, leaves, and roots that accumulate on the soil surface. On average, lawn dethatching costs $170 per hour or between $0.04 and $0.06 per square foot.
- Aeration pulls plugs from the soil to create holes that allow more water and air to reach below the soil at the root level.
Be sure to use these two practices in conjunction with overseeding. Aeration can bring weed seeds to the surface, so you’ll want to overseed and fill the lawn with nice, thick grass, which provides competition and shade for crabgrass seeds.
Fertilize
Fertilize your lawn to keep everything in top shape. First, get a soil test to determine the condition of your soil, the soil pH, and what nutrients it may need. Then, purchase an appropriate conventional or organic fertilizer to keep your lawn full and thick.
Fill in the bare patches
As mentioned, creating thick turf is critical to providing maximum crabgrass competition. Many experts emphasize that a full, dense lawn inhibits crabgrass germination. Remember, crabgrass thrives in the sun and dies in the shade. Let your lawn do some of the work for you — make sure the grass is thick and thriving, and it will prevent new weeds from sprouting.
For thin lawns, this means overseeding to create dense turf. It also means planting grass seed in areas after removing existing crabgrass. Bare spots create a perfect void for new crabgrass plants to sprout.
Be persistent
Crabgrass control is an ongoing endeavor. Crabgrass seeds in the soil can stay dormant for several years, so expect to repeat this process annually. Persistence is critical to reducing your crabgrass population over time.
FAQs about getting rid of crabgrass
What will kill crabgrass but not the lawn?
To target crabgrass in your lawn, choose a selective, post-emergent herbicide formulated to control grassy weeds. Some recommended herbicides include Ortho Weed B Gone Plus Crabgrass Control and Image Lawn Weed & Crabgrass Killer.
What is the difference between crabgrass and quackgrass?
Both weeds have wide, grasslike blades, but that’s where the similarities end. Crabgrass is light green or greenish yellow; quackgrass is bluish-green. Crabgrass is a warm-season annual; quackgrass is a cool-season perennial. Crabgrass grows horizontally, close to the ground; quackgrass grows upright.
Does mowing crabgrass spread it?
Yes, mowing can spread crabgrass if it has already developed seedheads and you don’t bag the grass clippings. If the plants haven’t developed seedheads, mowing will not spread it across your lawn.
Need help conquering crabgrass?
Crabgrass is a persistent, pesky lawn weed, but you can use natural and conventional methods to eliminate existing crabgrass and prevent it from becoming a future problem. Above all, be persistent, and don’t underestimate the power of simple, routine landscaping practices to aid you in the fight against this weed.
If crabgrass is too much for your to-do list, contact a local professional to conquer your crabgrass and restore your lawn.
Main Photo Credit: Rasbak | Wikimedia Commons | CC BY-SA 3.0
