How Crabgrass Works
Crabgrass spreads quickly during the warm summer months. Between midsummer and early fall, each crabgrass plant produces thousands of seeds. The first frost kills the plants, but the seeds remain dormant through the winter. When the ground temperature warms up, the seeds begin to grow. The key to crabgrass control is making sure the seeds can’t germinate. There are several ways to prevent crabgrass seed germination.
Here are the three things to remember:
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Kill crabgrass before it comes up with a pre-emergent herbicide.
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Kill crabgrass after it comes up with a post-emergent herbicide.
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Grow a healthy lawn to keep crabgrass from coming back.
How to Get Rid of Crabgrass: Use a Pre-Emergent Herbicide
If crabgrass has become established in your lawn, proper lawn maintenance alone may not be enough. You’ll need to use a preemergent herbicide as the next line of defense. A preemergent herbicide crabgrass killer works by eliminating the crabgrass seedlings as they germinate. When applying preemergent herbicide, always follow the manufacturer’s directions. In general:
- Timing is essential when using preemergent herbicides. Application times depend a great deal on weather patterns, which vary from region to region. If your area has experienced a warm winter, you’ll probably need to apply the herbicide earlier than usual.
- When getting rid of crabgrass, apply the herbicide when the ground temperature rises above 60 degrees Fahrenheit. Since it’s hard for most of us to monitor the soil temperature, just watch your landscape. When you notice shrubs blooming and trees budding, it’s time to apply the herbicide. Warm nights and periods of rainfall encourage crabgrass germination. If the weather in your area fits this pattern, you’ll need to apply the herbicide right away.
- For newly seeded lawns, wait until you’ve mowed your lawn three times before applying the herbicide to avoid killing the new grass seedlings.
- Apply the herbicide uniformly across your lawn. If you miss a spot, crabgrass can get established and then spread to the rest of your lawn.
- Wear protective equipment, including gloves, a long-sleeved shirt and a mask.
- Don’t dethatch or aerate the lawn after applying the herbicide. This can break the chemical barrier of the herbicide and render it ineffective.
- Wait two to four months to reseed the lawn after using a pre-emergent herbicide. This timeframe may differ, depending on varying circumstances, so always refer to the manufacturer’s instructions.
- Use a preemergent herbicide during late winter or during the early spring of the next year to prevent any remaining crabgrass seeds from developing at the next opportunity.
- Don’t use a preemergent herbicide if crabgrass is already in the lawn or if you’ve just installed sod.
When using lawn treatments or lawn-care products, always follow package directions regarding proper clothing, protective equipment, application procedures and safety precautions. When using herbicides, also make sure you understand which weeds the chemical treats and which desirable plants it may also kill.
Know your grass. It’s important to properly identify your grass so that you know how to get rid of crabgrass in the lawn before you apply a herbicide. Some herbicides work for two or three types of grass but may kill two or three other types of grass. Know which herbicide works best for your type of grass before you apply.
How to Get Rid of Crabgrass: Use a Post-Emergent Herbicide
If the crabgrass seeds have already sprouted and crabgrass has appeared in your grass, the pre-emergent herbicide will do no good. However, you can learn how to kill crabgrass with post-emergent herbicide products, which control crabgrass after it’s already germinated.
Post-emergent herbicides work by killing the crabgrass plants. Apply these herbicides only to the crabgrass that’s visible. Read and follow the manufacturer’s directions on the product carefully. The amount of post-emergent herbicide that you can safely apply to your lawn depends on the type of grass you have. Here are some tips:
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Check the weather forecast before using a post-emergent herbicide. You want to apply it on a calm, sunny day. Rainfall shortly after application will wash the product away before the crabgrass has a chance to absorb it.
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For best results, apply the herbicide in the morning after the dew has dried. If you wait until late afternoon, dew or a shower may prevent maximum absorption.
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Post-emergent herbicides work best when temperatures are between 60 and 90 degrees Fahrenheit. High temperatures cause the plants to absorb the herbicide quickly. If it’s too cool or cloudy out, the product will likely be ineffective.
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Make sure the soil is moist before applying the herbicide. If it isn’t, you should water the area fairly extensively using a garden hose or sprinkler system on the day before treatment. If conditions are extremely dry, you may want to water again two days after the application. The waiting period will give the crabgrass time to absorb the herbicide.
- If you notice the lawn browning suddenly, you may have applied too much herbicide. In this case, water the area extensively as soon as possible to dilute the herbicide and keep it from further damaging your lawn.
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After treating the area with herbicide, keep an eye out for newly germinated crabgrass plants. Any plants that may have germinated since the initial application will require a follow-up spot treatment.
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If the crabgrass plants are fairly well established, you’ll need to apply the herbicide twice. Treat the affected areas again four to seven days after the first application. Make sure the soil is moist before the second application.
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Follow the manufacturer’s instructions about when it’s safe to reseed grass. Seed new grass in the area as soon as possible to establish a healthy lawn that crabgrass can’t break through.
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If you use a post-emergent herbicide during the summer, care for your lawn according to the lawn-maintenance tips above.
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If the majority of your lawn is crabgrass, it may be best not to remove it during the summer. It’s best to wait and renovate the lawn in the fall.
How to Get Rid of Crabgrass Naturally
If you want to know how to get rid of crabgrass naturally, there are a few methods you can use that are effective. For many, you need look no further than your kitchen pantry.
- Manually hand-pulling crabgrass by the roots is one of the most effective ways to kill crabgrass. However, if your lawn is covered with crabgrass, this may not be the most efficient way to get rid of it as it will be too time-consuming and labor-intensive. Hand-pulling is also an effective way to get rid of crabgrass in flower beds.
- Using corn gluten meal acts as a natural pre-emergent herbicide that prevents crabgrass seeds from germinating. Scatter it over the soil and water it to prevent roots from growing.
- Lightly dampen the crabgrass then sprinkle baking soda on it.
- Dry out the crabgrass by spraying a mixture of white vinegar and liquid soap on it.
Prevent Crabgrass in the Future
The best defense against crabgrass is a healthy lawn. Unwanted grasses and weeds simply can’t thrive in a robust stand of grass. Follow these basic lawn-care guidelines to keep crabgrass from becoming a problem in your yard:
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Use a lawn mower to mow your lawn at frequent intervals to keep the grass a fairly consistent length. Check the recommended mowing heights for your type of grass and cut your lawn at the highest recommended setting. Crabgrass requires plenty of light to germinate, so keep the grass as thick and long as possible to create shade near the soil surface. Cutting your lawn too close will produce patches where crabgrass and other weeds can germinate.
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Don’t cut more than a third of the grass height when mowing. Removing more grass not only allows more light to reach weeds but can also injure the grass.
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Water established lawns in long, heavy intervals rather than shallow, frequent ones. Watering on an irregular schedule and only when needed promotes deeper root growth that’s essential to healthy turfgrass. Remember that most established lawns require about 1 inch of water per week from rain or irrigation. If your lawn is newly seeded, water in shallow, more frequent intervals until the grass gets established.
- Use fertilizer at least once a year, following the package instructions.