Crabgrass is a common lawn invader that spreads rapidly, disrupting the growth of desirable grasses. Understanding how it thrives and spreads helps us take control and maintain a healthy, vibrant lawn. Crabgrass may look harmless, but at Lush Lawn, we understand how quickly it turns from a patch of green into a full-scale invasion.
Key Takeaways
- Crabgrass thrives in bare or thinning turf
- It germinates when soil temperatures rise above 13°C
- One plant can release thousands of seeds
- Pre-emergent herbicides are key to prevention
- Ongoing lawn care strengthens resistance
Understanding Crabgrass: The Basics
First, let’s take a moment to understand what we’re up against. Crabgrass (Digitaria spp.) is a warm-season annual grass that thrives in hot weather. Unlike our cool-season grasses, which stay green and lush during the spring and fall, crabgrass loves the heat of summer. It germinates in the spring when soil temperatures reach about 55°F to 60°F, usually around the time our cool-season grasses start to slow down or go dormant in the warmer months.
Crabgrass grows quickly and aggressively, forming low-lying, spreading clumps of grass that often look different from the rest of our neatly manicured lawn. If you’ve noticed that your lawn is dotted with these fast-growing patches, it’s likely crabgrass trying to claim its space. Once it establishes itself, it can crowd out our desired grasses, leaving us with an unsightly, patchy lawn.
How Does Crabgrass Spread?
The real challenge with crabgrass isn’t just its growth, it’s how it spreads. We all know how weeds seem to pop up out of nowhere, but there’s a science to this process. Crabgrass spreads primarily through seed production. Each mature plant can produce thousands of seeds, and once these seeds are dispersed, they have a long lifespan, often lying dormant in the soil for months or even years before they germinate. This is part of what makes crabgrass so persistent.
When the weather gets hot, and our lawns start to dry out, crabgrass can take advantage of these conditions. It doesn’t require much water once it’s established, making it a prime competitor for nutrients and space. The seeds germinate in bare or stressed patches of lawn, typically where the soil is disturbed or where the turf is thinning. These areas provide the perfect opportunity for crabgrass to grow, and it doesn’t waste time, once it starts growing, it spreads quickly, creating new seeds that continue the cycle.
One of the most common ways crabgrass spreads, however, is through human activity. If we walk across an area of crabgrass, we can unknowingly carry seeds on our shoes, mowers, or garden tools. Over time, these seeds are deposited in new areas of our lawn, where they germinate and start the cycle again. This is why regular lawn care services are important to help keep weeds under control, as a proactive approach can prevent the spread of crabgrass and other invasive plants. So, even if we try to be diligent about removing crabgrass, we might be inadvertently helping it spread.
How Does Crabgrass Survive?
Crabgrass has a remarkable ability to survive even in less-than-ideal conditions. This is why it’s such a formidable foe in our lawns. Unlike our cool-season grasses, which require moisture and cooler temperatures to thrive, crabgrass has adapted to hot and dry conditions. Once established, crabgrass can survive drought better than most cool-season grasses, making it especially resilient in the summer months when water can be scarce.
The plant’s root system also gives it an advantage. Crabgrass has a fibrous root system that’s relatively shallow but spreads widely, which helps it quickly absorb water and nutrients. This allows it to outcompete other plants in the lawn for resources, especially during dry spells.
Another key factor in crabgrass’s survival is its seed production. As mentioned earlier, crabgrass can produce thousands of seeds per plant, which means that even if we manage to pull out the visible weeds in our lawn, there’s a high chance that new seeds will sprout up next season. These seeds can remain dormant in the soil for several months or even years, just waiting for the right conditions to germinate and continue the cycle of invasion.
Crabgrass also thrives in disturbed soil. Whether it’s from heavy foot traffic, a broken sprinkler system, or lawn aeration, any action that disrupts the soil provides an opportunity for crabgrass seeds to take root. That’s why it’s important to keep the lawn thick and healthy, if the grass is dense, crabgrass won’t have as much space to grow.
How Can We Control Crabgrass?
Now that we understand how crabgrass spreads and survives, let’s talk about how we can take control of this pesky invader. Here are a few strategies we can implement to manage and prevent crabgrass from taking over:
-
Prevention is Key: Use Pre-Emergent Herbicides
The best way to control crabgrass is to prevent it from sprouting in the first place. Applying a pre-emergent herbicide in early spring, when the soil temperature reaches around 55°F to 60°F, can stop crabgrass seeds from germinating. This is the most effective way to prevent crabgrass from taking root in our lawns. However, we must be cautious when using herbicides, as they can also affect the germination of desirable grasses. Be sure to follow the instructions carefully.
-
Maintain a Healthy Lawn
Crabgrass thrives in lawns that are stressed or unhealthy. By keeping our grass thick and well-nourished, we can reduce the chances of crabgrass taking hold. Regular mowing, watering, and fertilizing are essential for keeping our grass healthy. The denser our lawn, the harder it is for crabgrass to establish itself.
-
Spot-Treat Existing Crabgrass
If crabgrass has already made its way into our lawn, we can spot-treat the individual plants. There are post-emergent herbicides available that can effectively target and kill crabgrass without harming other plants. However, timing is crucial. The earlier we catch the crabgrass, the easier it is to manage.
-
Reseed Bare Patches
One way to prevent crabgrass from returning next season is by reseeding any bare or thin areas of our lawn. These spots are prime real estate for crabgrass to take root, so by filling them in with desirable grass, we reduce the opportunity for crabgrass seeds to germinate.
-
Water Wisely
Crabgrass doesn’t need as much water as other grasses, so we must water our lawns deeply and infrequently to encourage the growth of our desirable grass species. Shallow, frequent watering promotes crabgrass growth, so aim for deep watering sessions that soak the soil to a depth of several inches.
Conclusion
Crabgrass isn’t just a nuisance, it’s a survivor. It takes advantage of weak lawns and multiplies fast. But with a science-based approach and timely action, we can stop it in its tracks. If you're seeing signs of invasion or just want to safeguard your lawn, get in touch with our experts at Lush Lawn. We'll assess your lawn and build a plan that restores its strength, season after season.
FAQs:
What causes crabgrass to spread so fast?
Crabgrass produces a high number of seeds and grows quickly in warm, open spaces. Weak turf or bare soil accelerates its spread.
When is the best time to apply pre-emergent herbicide?
Apply in early spring, just before soil temperatures hit 13°C. Timing is critical, too early and it won’t be effective, too late and seeds may sprout.
Can mowing prevent crabgrass?
Yes, mowing at a higher height can shade the soil, which prevents crabgrass seeds from getting enough light to germinate.
Does crabgrass die in winter?
Yes, crabgrass is an annual weed. It dies with the frost, but its seeds survive and return the next season.
Is crabgrass harmful to pets or people?
It isn’t toxic, but it disrupts turf health, leading to uneven surfaces and less usable lawn space.
How can I tell crabgrass apart from regular grass?
Crabgrass has broader blades, a sprawling growth habit, and tends to form clumps that sit lower to the ground.