Crabgrass is an annual grass that becomes invasive when allowed to produce seeds. The grass has a long germination period and will grow back each year if control measures are not taken. The process of killing the weed can be extensive since you need to wait to see if new growth appears from seeds that germinate underground. It's best to take preventive measures to block further seed germination once crabgrass has been eliminated from the flower bed.
Pull crabgrass shoots as they appear, making sure you remove the roots. It is best to remove the grass before it produces seeds. Use a garden trowel to loosen the roots if necessary.
Spray herbicide on sections of crabgrass that are difficult to remove. Take caution during application as you don't want to kill other plants.
Use an edge cutter around the flower bed to separate lawn grass from the flower bed. This will prevent grass from growing into the flower bed.
Apply 2 to 3 inches of mulch around the flowers once all grass remains have been removed. This will block the growth of weeds, including crabgrass.
Apply a pre-emergence weed killer in the spring if there is a known crabgrass problem. The application must be made before the crabgrass appears.