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Do It Yourself

How to Prevent Crabgrass

by Ed . | Apr 09, 2012

Crabgrass thrives in sparse lawns and, like most weeds, spreads extremely fast. As with most problems in the garden, prevention is the best defence. Although crabgrass can be gotten rid of after it has emerged, it's much easier to take steps to prevent it from ever growing at all. The key is to have a thick, healthy lawn and apply a pre-emergent granular herbicide when the soil temperature rises to 55 degrees Fahrenheit. This should keep your lawn should pristine all year long.

Here are a few tips to keep in mind when dealing with crabgrass:

  • Select an herbicide that contains prodiamine, dithiopyr, or oxadiazon. Most brands come with a "crabgrass preventer" label on the bag. If preferred, try an organic alternative such as corn gluten meal.
  • Apply the herbicide with a broadcast spreader once the soil temperature reaches 55 degree F. A good trick to use when trying to decide when to spread the herbicide is to apply it when your forsythias start to bloom. Forsythia shrubs produce yellow flowers when the soil temperature approaches 55 degrees F, indicating that crabgrass will germinate in the following weeks.
  • Water the herbicide into the lawn immediately after application. One-half inch of water will suffice.
  • Herbicide works great, but likely won't kill all the crabgrass. Set your mower at 3 inches for the growing season to shade out any crabgrass that survives.
  • Irrigate the lawn deeply and infrequently. Crabgrass seeds flourish in moist lawns that receive frequent irrigation.
  • As stated above, crabgrass thrives in sparse lawns, so make sure to add grass seed to any bare spots in the fall to prevent it from coming back next season.
  • Use crabgrass preventer in subsequent years, or stop once the turf has become dense enough to crowd out any seedlings.

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