When Does Crabgrass Germinate? What to Know

One of the best ways of controlling crabgrass is to apply a pre-emergent herbicide that kills the weed at the germination stage. Traditionally, crabgrass produces thousands of seeds before the plant is killed by frost. So, when does crabgrass germinate?

Crabgrass germinates when the soil temperature warms up to at least 55°F for 4 or more consecutive days. This is the time you will also see other weeds sprouting by your paved areas like sidewalks.

When Does Crabgrass Germinate?

It is important to know when crabgrass dies, germinates and thrives. When using pre-emergent herbicide for crabgrass control, you must apply it right before the germinating seed emerge. The herbicide has to be watered into the soil to interact with the germinating seeds.

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 condition may vary from one region to another based on geographical location.

A change in soil temperature can 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. Shrubs like Forsythia will also start blooming in your area at this soil temperature.

Crabgrass Control – How to Manage It

With hundreds of thousands of crabgrass seeds potentially waiting in your lawn, any miscalculation in the application of crabgrass preventer may lead to some seedlings sprouting. At that point, you will have to use post-emergent herbicides.

The best way to control crabgrass is to prevent it from growing. You can effectively do it by applying a crabgrass preventer also known as a pre-emergent herbicide. The herbicide doesn’t necessarily interfere with the germination process but rather stops the formation of new root cells in baby weed plants.

This means, seedlings cannot continue to feed and grow and they just die back. However, timing is important for the successful use of pre-emergent crabgrass herbicide.

You should spray a crabgrass preventer in spring when the soil temperature reaches 55 to 60 degrees Fahrenheit for three to four consecutive days. Apply before rains and early in the morning when the weather is sunny and calm.

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 sprouted.

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.

Before using a 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 for other lives in the ecosystem. Herbicides can wash into nearby water sources to harm aquatic animals.

Using herbicides also affects other nontargeted plants. This makes it important to think of controlling crabgrass naturally as follows:

  • Mow high – Crabgrass loves warm soil and sunlight. Mowing low or scalping your lawn only encourages the weed to thrive. You should mow high to encourage a thick lawn which helps in keeping the 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 compete effectively and defeat these opportunistic weeds.
  • Fix bare spots – Thin and bare spots in the lawn encourages the growth of crabgrass. You should seed all the thin and bare areas early enough to counter the threats of weeds.
  • Fertilize your lawnGood 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 the flow of important supplies to the grassroots.

Final Thought

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.


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