pre-emergent crabgrass killer
Look at our website for crabgrass control and Tips for application. During and shortly after, forsythia bloom is a rough, but not consistently reliable, guide for application timing. You will have to look at soils temperatures too. If you do not have a soil thermometer, you may have to rely on the above. There are numerous products on the market. Look for a product without fertilizer. http://extension.umd.edu/hgic/crabgrass
See more on the following publication http://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/non_HGIC_F...