Posted on December 8, 2023 by rgrandy
As the days get sunnier, dormant plants begin to emerge, bringing new life to the yard. Unfortunately, invasive weed species also make a comeback, including crabgrass. Crabgrass is one of the most troublesome weeds to lawn enthusiasts who take pride in achieving perfectly manicured grass.
Crabgrass germinates in spring and grows throughout the summer. It thrives in dry conditions and poor soil, mostly invading neglected yards. The weed is very difficult to destroy because its seeds can remain dormant in the soil for up to 15 years.
Lawn Doctor insight: In most regions, crabgrass begins to germinate once soil temperatures reach 55°F at a 2-inch depth for several consecutive days. This temperature marker, not the calendar, is the most reliable sign that pre-emergent applications must be in place.
Crabgrass seeds flourish until they die, leaving big leaves and circular dead spots in the yard. It will return the following year from the seeds it embeds if not tended to properly.
We advise lawn owners to get rid of the weed before it’s established as the only way of stopping it from overtaking your lawn during the summer months.
Lawn owners can identify crabgrass by looking for its namesake, long-reaching, spindling stems. The grass crawls out of the ground and across other grass species, much like a crab walking across the sand. It sprouts from a single root with a dark green appearance. It’s easily distinguishable because it grows out and appears clumpy, while lawn grass blades grow upright.
Its aggressive and invasive nature allows it to choke out desired grass species and other native plants. Allowing it to run rampantly unchecked will negatively impact your lawn’s health and surrounding plants.
Crabgrass closely resembles other common lawn weeds and can easily be confused with them if not properly identified. This section lists other weed species resembling crabgrass, providing distinguishing factors between the weed and its look-alikes.
Johnsongrass: Much taller than crabgrass, with wider leaf blades and a white line down its middle.
Tall fescue: Darker green hue and grows year-round.
Nimblewill: Short with narrow, bluish-green leaves; looks like brown dead spots in winter.
Quackgrass: Grows upright instead of outward like crabgrass.
While preventative measures are the most effective way to stop crabgrass from spreading in the lawn, they can also be controlled using post-emergent and weeding methods.
The method you use to remove crabgrass from your lawn will depend on a few different factors. If the infestation is especially pervasive, consulting a professional will save you a ton of headaches and ensure the job gets done right.
We advise lawn owners to spread organic pre-emergent herbicides early in the spring to block crabgrass from germinating in the first 6-week germinating period. This gives the lawn a head start, allowing it to thicken up and prevent sunlight from getting to the crabgrass seeds later in the spring.
Lawn Doctor insight: For chemical pre-emergents, products containing prodiamine or dithiopyr are among the most frequently used in professional lawn programs. These are highly effective when timed correctly.
However, pre-emergent herbicides only block crabgrass germination. Therefore, applying them after the crabgrass seedlings have started growing does not affect them. The more natural option would be to hand-pull the crabgrass seedlings that have already started growing.
Lawn owners can weed the seedlings by hand, especially if they haven’t gotten out of control. The seedlings should be fairly easy to remove while they’re still young. Just ensure you pull up the entire seedlings with the roots intact. Otherwise, it will regrow from the remaining roots.
Lawn owners can also use controlled burning to control and destroy crabgrass before it gets out of hand. However, this method comes with many risks, including scorching surrounding grass and desired plants in an already struggling yard. Burning is also more hazardous, especially in dry summer weather, but it’s a very effective controlled solution if done safely.
Typically, crabgrass seeds germinate in late winter but vary from year to year, depending on rainfall, temperature, and location. They germinate when soil temperatures reach 55°F at a 2-inch depth for at least 3 days.
Lawn Doctor regional timing insight: Because germination windows shift annually, professionals rely on soil temperature tracking and weather patterns — not dates. In many markets, Lawn Doctor recommends applying pre-emergence before April 20, with a second application roughly 60 days later in areas with heavy pressure.
Getting the timing right is crucial to successfully controlling the weed.
Lawn owners should also apply crabgrass pre-emergence herbicides in areas that have had the weed in prior years. It’s worth mentioning that these pre-emergence products don’t kill the crabgrass plants or seeds. Rather, they kill the plants just as they’re emerging from the seeds. As such, pre-emergent herbicides won’t affect already existing crabgrass plants.
As with all chemical applications, we advise lawn owners to pay close attention to the product labels and directions.
Lawn Doctor note: Some products require two applications, while others need only one. Professionals tailor treatments to the turf type, soil conditions, and past lawn history.
New lawns: Seed in fall and apply pre-emergents in spring to avoid harming new seedlings.
Crabgrass seeds can remain viable in the soil for up to 15 years and often blow along the streets, resting near driveways until they have the right amount of soil contact, water, and heat.
Crabgrass seeds grow more quickly than other lawn grass species, which is when most lawn owners notice the plants. The weeds start spreading low to the ground, and mower blades miss them, letting the plants thrive and spread.
The weed can withstand areas with heavy foot traffic, and each plant produces thousands of seeds after the growing season as it prepares for the next season.
As one of the most challenging weeds to control, crabgrass has proven tricky to control and prevent. Its straightforward life cycle only adds to the challenge, as temperature changes, soil moisture and timing give it its resilient form.
These steps should help lawn owners remove and prevent crabgrass from invading property and damaging lawns.
Spring temperatures can be a wildcard, depending on your location. Some areas can have temperatures as high as 90°F when spring approaches or as low as freezing during cold spring nights. A key factor is to use the soil temperature as a road map for when to apply the crabgrass control.
Closely monitoring soil temperature helps eliminate perceived fluctuations in air temperature that can sometimes be misleading. We advise lawn owners to apply crabgrass preventers when the soil reaches 55°F for 5 consecutive days for the best results.
Lawn Doctor insight: Because soil temp varies widely by region, Lawn Doctor applicators monitor local conditions to ensure applications go down at the right moment to form a consistent barrier.
Crabgrass loves having moisture in the soil to germinate, but its resilience to drought allows it just as easily to withstand adverse changes in soil moisture compared to most lawn grass species. Watering the lawn lightly and repeatedly may promote shallow root growth, making the lawn more vulnerable to damage during the dry, hot months.
We encourage homeowners to water their lawns thoroughly and infrequently to allow grass species to develop deeper roots and crowd out crabgrass and other weeds.
After removing visible crabgrass weeds by hand or with a shovel, it’s important to seed all bare spots in the lawn as soon as possible. The idea is to prevent crabgrass from overtaking the damaged areas. Plant desired grass seeds and water the yard to encourage deep root development and crowd out germinating crabgrass seeds.
A crabgrass preventer is a pre-emergent herbicide that controls and prevents crabgrass seeds and plants from sprouting. We advise lawn owners to apply crabgrass preventer in early spring to get ahead of the crabgrass seeds and prevent them from germinating.
As aforementioned, apply the herbicide in the spring before the crabgrass sprouts for the crabgrass preventer to work. Homeowners should get the first application down before April 20, and reapply around 60 days later, reinforcing the barrier and building on top of the first application.
Lawn Doctor note: Prodiamine and dithiopyr are commonly used in professional applications because they provide reliable, season-long control when applied correctly.
We recommend using a garden seeder or lawn spreader to apply the preventer. Apply it uniformly across the lawn without missing any spots. After applying the crabgrass preventer, hydrate the lawn consistently to ensure it’s activated evenly.
Always follow manufacturer instructions.
Crabgrass is a frustrating annual weed that affects lawns and thrives in dry weather. It can crop up in the lawn, between patio slabs or anywhere in the right conditions, and it becomes difficult to remove wherever it sprouts.
Homeowners with a newly spread lawn should wait until they have mowed it a few times before applying a crabgrass preventer. Otherwise, the preventer may kill desired grass seedlings alongside the weed.
It’s important to control the weed as soon as possible before it hogs all precious nutrients the soil should be getting and supplying to desired grass species.
Crabgrass is a persistent lawn problem for several reasons, including the fact that its many seeds can remain dormant in the soil for several years.
Lawn Doctor recommendation: Use effective crabgrass pre-emergent herbicides at the right time and amount — otherwise the weed will return. Lawn Doctor offers customized treatments based on turf type, climate, and past weed activity.
Contact Lawn Doctor to help care for your lawn when you can’t.
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