The Fight against Crabgrass

Crabgrass is an eye sore and will easily take over your lawn.  It developed in Europe; and unfortunately, we have it in the United States. Crabgrass will start to germinate when soil temperatures reach an average of 55°F; which means to combat the nuisance weed, a pre-emergent such as Dimension or Pendimethalin must be put down before the soil reaches germination temperature.  A good rule of thumb is 52°F.  This way, when the crabgrass germinates, it absorbs the herbicide and dies.

Pre-emergents are not 100% guaranteed to totally eradicate the weed.  Pre-emergents form a barrier against crabgrass which can be broken down by weather or mechanical factors.  Heavy rains in spring may break the barriers, as can foot traffic, mowers, pets, etc.  A second pre-emergent application may be necessary. 

Factors that contribute to crabgrass infestations are clay soil, compaction, thin lawns, high temperature areas (along asphalt and concrete), mowing too short, and drought.  There are more factors, but these are some of the most common ones.

If your lawn is thin, you may want to aerate and overseed in the fall, or slit-seed.  We have seen that using a pre-emergent in the fall has helped on badly infested lawns.  A good lawn program is the best way to manage crabgrass, along with other undesired pests. 

Example of a lawn program:

  • Mid- March:  pre-emergent with slow release fertilizer

  • Late-April:  broadleaf weed control (may need a second pre-emergent application or fertilizer)

  • Early-June:  weed and feed

  • August:  weed and feed

  • October and beyond:  winterizer fertilization

These dates above may vary due to weather conditions.  Your lawn care provider will adjust so you get the most out of your treatments.

Note:  Pre-emergents will stop the germination of regular grass seed, so seeding should be done 6 to 8 weeks after any pre-emergent applications.

Robin Falk 

ALawn Landscape LLC - Salem OH

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