Controlling Crabgrass

Crabgrass is an annual grass that germinates from seed each year and typically dies by the end of September when we get our first few nights of frost. The key to making sure that crabgrass doesn’t become a problem in your lawn is to keep the seeds from germinating. You can prevent crabgrass seeds from germinating in a number of ways; the best defense against crabgrass is a healthy lawn.

  • Mow your lawn at frequent intervals and keep it a minimum of 2.5” tall – 3” is even better. Crabgrass seeds require an exceptional amount of light to germinate, and having a healthy tall stand of grass is a great defense, shading light from reaching the soil surface. If your lawn seems thin or has patches with no grass, a core aeration and over-seeding will be a great benefit.
  • Be sure to water an established lawn deeply and less frequently. This will encourage deeper root growth increasing the health and resistance of your turf grasses.
  • Following a sound fertilization program will also increase the health and vigor of your desirable grasses and decrease the chance that any weeds such as crabgrass can take hold.
  • Overly dry soil can also lead to cracks in the soil surface where crabgrass seeds easily germinate. Compacted soils that hinder desirable grasses also provide an environment where crabgrass is likely to thrive.

If Crabgrass becomes established in your lawn, or has been in past years, simple maintenance and cultural options typically will not be enough.

A pre-emergent herbicide is the next line of defense. Pre-emergent herbicides work by killing the crabgrass seeds as they germinate, but will also hinder other desirable grasses from germinating as well. This is why we recommend core aeration with over-seeding to be done in fall. This allows you to control the crabgrass during the time of year when it grows. Our first application each year, contains a pre-emergent herbicide unless there are circumstances that prevent its use (i.e. organic only customers, or newly installed seed or sod).

  • It is important to apply pre-emergent before the soil temperatures reach 55-60 degrees, which is when crabgrass seeds begin to germinate.
  • Newly seeded lawns will need to be mowed three times before an application of pre-emergent to ensure no damage is done to the new grass seedlings.
  • If you must reseed small areas in your lawn, use a leaf rake to disturb the soil surface in as small an area as possible. Rake in the new seed, keeping moist for up to 30 days.

Keyman Fertilization & Weed Control, LLC

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