What is Crabgrass and why is it so bad this year?

Crabgrass is a grassy weed that can be found throughout most of North America. Crabgrass is very distinct in home lawns because it is darker, thicker, and taller than Kentucky bluegrass or Bermuda grass. Crabgrass also grows in clumps so it appears in distinct patches.

Crabgrass germinates in the late spring as temperatures turn from warm to hot and it really thrives in bare and thin areas of the lawn. Often times you will find crabgrass near patios, walkways, and sidewalks because those areas absorb more heat from the sun and you will always find more Crabgrass in dryer seasons. As the season progresses, Crabgrass will grow thicker and fuller until it eventually goes to seed later in the summer. As temperatures begin to cool in the fall Crabgrass will start to turn purple and eventually die off, but the seeds left behind will germinate in later years.

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How do I prevent and control Crabgrass?

As with any weed control, the best way to prevent Crabgrass is to have a thick, healthy lawn. This can be achieved through proper fertilization and cultivation practices. If you cut, water, seed and fertilize according to your lawn’s requirements you should be able to avoid Crabgrass altogether. In addition to proper cultural practices, Crabgrass can be prevented by applying a good pre-emergent herbicide in the spring and then controlled by a good post-emergent herbicide in the summer. Pre-emergent herbicides create a barrier that helps prevent the seeds from germinating in the soil and post-emergent’s are products that can be applied to the weed once it has grown. Since pre-emergent’s are only partially effective, you will likely need to apply post-emergent’s as a follow up in the summer. Finally, if you have a crabgrass problem it is crucial to seed the lawn after the Crabgrass has been controlled. If you don’t seed the lawn, Crabgrass is almost certain to return in that area.

 Steps to be taken if you think you have a crabgrass problem:

  • 1. Apply pre-emergent herbicides in the spring to prevent Crabgrass from growing.
  • 2. Aerate and over-seed the lawn in the spring or fall to thicken the turf. This will reduce the space needed for Crabgrass to grow.
  • 3. Fertilize regularly according to your grass type’s specific requirements.
  • 4. Do not cut the lawn too short (2.5 to 3 inches for Kentucky bluegrass, 1.5 to 2 inches for Bermuda grass and 2 to 3 inches for St. Augustine).
  • 5. Apply post-emergent herbicides in the late spring and summer once Crabgrass begins to grow. Getting it early helps because the weed becomes harder to control as it gets more established.
  • 6. Water up to 2 times per week to a depth of 2 inches.

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