You should use a pre-emergent crabgrass herbicide before the grass germinates, late February to early March in West Tennessee and mid-March to early April in East Tennessee. You can use a post-emergent herbicide any time after the grass germinates.
About this Author
Melody Lee worked as a newspaper reporter, copywriter and editor for 5 years. In addition, she has edited magazine articles and books. Lee holds a degree in landscape design and is a Florida master gardener. She has more than 25 years of gardening experience, which includes working at nurseries and greenhouses.