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Annual Crabgrass in Turfgrass
By Don Schlup
crab-grass

Appearance

  • Crabgrass is an annual grass that germinates in late spring invading home lawns. It reproduces by seed at a prolific rate and will quickly invade open, thin areas of the turf and along edges of sidewalks and driveways.
  • It can be identified by its wider leaf blades and clump-like growth followed later by purplish seed heads resembling turkey feet.

Problem

  • Crabgrass shows up in lawns in mid to late spring after the soil temperature has been consistently warm. It germinates best when lawns are watered lightly and frequently.
  • It thrives best in full sun and is quick to invade lawns that are mowed too short and lawns that are thinning out. This allows the seeds to germinate and the crabgrass to fill in the spots.
  • It is an annual, which means it will die out with the first hard frost in autumn, but the seeds can survive for next year to re-grow again.

Solutions: Pre-emergence Herbicides and Application Times

  • The best control is PREVENTION: apply a pre-emergent crabgrass control in early spring when the forsythia shrubs are in bloom. On south and west exposures of the lawn, you will need to apply much earlier in late March through April depending upon weather conditions in your area.
  • APPLY A SECOND APPLICATION FOR PROBLEM AREAS.
  • Re-apply the pre-emergent in mid to late-summer to provide additional protection against seeds that may have blown in with the wind.
  • Mow the turf as tall as possible to discourage germination of the crabgrass seeds. A mowing height of 2 to 3 inches is recommended to shade the soil and prevent crabgrass seed germination.
  • When the soil is moist, crabgrass clumps can be dug out or pulled by hand.
  • Post-emergent controls are a temporary way to eliminate crabgrass and will often discolor your bluegrass lawn. Summer crabgrass controls are sold under various trade names and should be used with care. Read and follow label directions.