Crab grass - Knowledgebase Question

Question by dammin
June 30, 2010
My garden had a area which was infested with weed (mostly clovers). I scraped out all of it and put in topsoil and reseeded with scotts smart seed. Now this area is infested with crabgrass which was not there before. What should I do? Please help. Thank you.

Answer from NGA
June 30, 2010


Crabgrass starts germinating when soil temperatures are 50 to 55 degrees F for ten or more days and germination can take place over a 6 week period. Pre-emergence herbicides provide excellent weed control for crabgrass but they last only about 30 days. The compound prevents the weed seed from germinating, but it will not kill the newly sprouted seedlings. Late March to early April is an ideal time to apply pre-emergence controls. The difficulty in controlling your crabgrass is that you want to overseed and the pre emergence herbicide will keep the grass seeds from sprouting. At this point, you might want to try raking it out or hand pulling. Use a corn gluten based pre emergent on your lawn to keep the crabgrass from sprouting and wait to overseed this fall. A dense stand of turfgrass will help keep the weeds from growing back. A fall fertilizing and overseeding can also limit spring problems. Best wishes with your lawn.

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