One of the best way of controlling crabgrass is to apply a pre-emergent herbicide which kills the weed at early stage of germination. Crabgrass produces thousands of seeds before the plant is killed by frost. The seeds remains dormant during the cold season and germinates when the weather warms up. So, when does crabgrass germinate?
Crabgrass starts to germinate when the soil temperature at a 2-inch depth reaches at least 55°F for 4 or more consecutive days. Without soil thermometer you can tell this when you see weeds sprouting by your paved area like sidewalks, patios or when shrubs like Forsythia start blooming in your area.
When Does Crabgrass Germinate?
Pre-emergent herbicides are effective at controlling crabgrass and other weeds before they emerge. The herbicide doesn’t necessarily interfere with germination process but rather stop the formation of new root cells in baby weed plants. This means, seedlings cannot continue to feed and grow and they just die back.
When using pre-emergent herbicide for crabgrass control, you must apply right before the germinating seed emerge. The herbicide has to be watered into the soil to interact with the germinating seeds. This is why it becomes important to know when crabgrass die, germinate and thrive.
Crabgrass usually germinates when the soil temperature at a 2-inch depth reaches at least 55 Degrees Fahrenheit for 4 or more consecutive days. This weather conditions may vary from one region to another based on the geographical location.
This change in soil temperature can only be determined by a soil thermometer. However, some traditional methods can help you know when soil temperatures are warm for crabgrass germination. Simply check if weeds are sprouting by your walkways, driveways and patios or when shrubs like Forsythia start blooming in your area.
What does Crabgrass Seedling Look Like?
With hundreds of thousands of crabgrass seeds potentially waiting in your lawn, any miscalculation in application of preventer may lead to some seedlings sprouting. At that point, pre-emergent herbicides no longer work. You will have to use post-emergent herbicides. But, what will you be dealing with?
At an early stage, it may be difficult to distinguish crabgrass from the other lawn grasses. Crabgrass can come in many shapes, sizes, and textures trying to adapt to your lawn’s conditions. Being an opportunistic weed, it will start emerging in bare spots of your lawn. This is where you should start to check.
After germinating, crabgrass seedling will look like a miniature corn stalk. As it grows, the leaves will start to branch out. Depending with the lawn conditions, a mature crabgrass can have smooth or hairy blades. When spreading out, crabgrass will form long branches that shoot out from the stem and turn in sharp angles, making the weed to look like crab legs.
Crabgrass has no specific color, it can range from light green to a deep dark green. Sometimes you may not easily identify this weed in your lawn. It is unfortunate that this weed thrives in hardy conditions where common lawn grass may not. That’s why it easily takes over a lawn during drought conditions.
Killing Existing Crabgrass
Once crabgrass has emerged, you should target to kill it early enough before it set seed heads. Apply a post-emergent herbicide in early summer when the seedlings have sprout. When using your crabgrass killer, it is important to understand whether the product is “selective” or “non-selective”.
Selective herbicides are formulated to target specific weeds or plant categories. Non-selective herbicides kill all plant types, including lawn grasses and other desired plants you want to keep. Actively growing crabgrass in your lawn calls for selective, post-emergent herbicides.
Before using an herbicide, carefully read the product labels, and make sure your lawn grass is among those approved on the list. Some lawn grasses, such as centipede grass and St. Augustine grass, are susceptible to herbicides that usually don’t harm other lawn grasses.
How to Prevent Crabgrass Naturally
Once established, getting rid of crabgrass can be a tall order. Further, using chemicals is unsafe to other lives in the ecosystem. Herbicides can wash into the nearby water sources to harm aquatic animals. They also affect other untargeted plants. This makes it important to think of controlling crabgrass naturally.
- Mow high – Crabgrass loves warm soil and sunlight. Mowing low or scalping your lawn only encourage the weed to thrive. You should mow high to encourage thick lawn which helps in keeping soil cooler.
- Water thoroughly – Crabgrass can thrive in drought conditions when the other grasses are stressed and struggling. Watering thoroughly during summer drought will make the grass to compete effectively and defeat these opportunistic weeds.
- Fix bare spots – Thin and bare spots in lawn encourages growth of crabgrass. You should seed all the thin and bare areas early enough to counter the threats of weeds.
- Fertilize your lawn – Good lawn fertilizing schedule thickens the grass and makes it difficult for weeds to sprout. Fertilize your lawn after the initial spring flush to discourage crabgrass from sprouting.
- Improve lawn soil conditions – Crabgrass thrives in compacted or clay soil. You should aerate your lawn to relieve soil compaction, improve drainage and enhance flow of important supplies to the grass roots.
Crabgrass can badly disrupt your lawn and even send your whole outdoor investment down the drain. Fortunately, you can control this dreaded weed by using herbicides but only after understanding its life cycle. It is also possible to prevent it through healthy lawn care practices.
- Texas AgriLife Extension: Crabgrass Germination Advice for Homeowners
- Michigan State Universty Extension: Timing crabgrass pre-emergence applications in spring
- University of Massachusetts Amherst: Biology and Management of Crabgrass