What analysis of fertilizer should I use to kill crabgrass and when should I put it out?
Calhoun County Michigan
Fertilizer does not kill crabgrass. Fertilizer is nutrients of nitrogen, phosphorus and potassium needed for plant growth. Spring fertilizers often include an added herbicide to prevent crabgrass. This is called a pre-emergent herbicide because it kills the plant as it begins to germinate from seed. There are a number of different herbicides used for this but the one thing they have in common is the need for correct timing. To control crabgrass the herbicide needs to be applied before it germinates. One indicator plant is the forsythia. Apply the fertilizer with the crabgrass pre-emergent herbicide about the time forsythia is in full bloom. A thick lawn mowed at 3 inches does a great job of preventing crabgrass from germinating. Crabgrass seed only germinates if exposed to light, which is common in a thin lawn or if it is mowed too short. For an article on different herbicides used for crabgrass control see the following site:http://planttalk.colostate.edu/topics/lawns/1541-pre-emergent-herbicides-crabgrass-prevention-lawns/