Controlling Large Crabgrass

Crabgrass has been considered one of the most troublesome weeds for several years. Crabgrass is a summer annual with a spreading habit with blue-green to purplish leaf blades. Crabgrass is normally found in thin turf grass or open areas. Lawns that are mowed two inches and shorter allow a lot of sunlight to reach crabgrass seeds that are trying to germinate. This can become a major problem.

Chemical Control Method

  • The main factor is controlling crabgrass before it sets seed. Apply pre emergent herbicides before crabgrass seed germinates. Normally, this will be when the top four inches of soil have reached 55°-60°. If there is an unexpected frost it could make the pre emergent useless. Be sure to irrigate after applying the pre emergent herbicide because water activates the pre emergent.
  • If you don’t happen to control crabgrass before it germinates you will need to use a post emergent herbicide. Use a Crabgrass Killer to eliminate this weed.

*After mid-July it is not very effective to use herbicides. At this point proper fertility, mowing, and irrigation will be the most effective measure until crabgrass dies with the first frost.


Organic/Cultural Control Method

  • Corn gluten acts as an organic weed and feed. It will prevent the crabgrass from germinating. Apply in late April/early May and again in the middle of August. It only prevents seeds not existing plants so be sure to apply before germination occurs. Buy Fire Belly Corn Gluten Now!
  • Also, remember mowing height is a huge factor in weed control! Keeping your mowing height around 3” will block sunlight from the crabgrass seeds that are trying to germinate.
  • Crabgrass loves to make its way to bare spots in ones yard. Be sure to overseed any bare spots you may have.
  • Fertilize your lawn. Avoid fertilization with nitrogen in the summer months.