How to Get Rid of Crabgrass

Crabgrass is best controlled by applying a pre-emergent herbicide in early spring before soil temperatures reach 55 degrees Fahrenheit, followed by post-emergent treatments to kill existing crabgrass. Maintaining a thick, healthy lawn through proper mowing, watering, and fertilization is essential to prevent crabgrass from returning.

Crabgrass is an annual grassy weed that spreads quickly and can overtake thin or stressed lawns if left untreated. The most effective way to control crabgrass is to prevent it with a pre-emergent herbicide in early spring, then use a post-emergent crabgrass killer to eliminate any weeds that have already sprouted.

• Spray a pre-emergent herbicide in spring to prevent crabgrass seeds from germinating
• Apply post-emergent herbicides on actively growing crabgrass weeds
• Improve lawn health to block future growth

Below, you'll learn when to apply crabgrass control products, how pre- and post-emergent treatments work, and which professional-grade herbicides are most effective for eliminating crabgrass and preventing it from returning.

Crabgrass pre-emergent herbicides stop crabgrass by preventing the seeds from germinating in the ground. Because crabgrass preventers do not kill existing weeds, application timing is critical for effective control.

To work properly, pre-emergent herbicides must be applied before soil temperatures reach 55 degrees Fahrenheit, which is when crabgrass seeds begin to germinate. In most areas, this occurs in early spring, though the exact timing varies by location. Your local extension office or soil temperature data can help determine the best application window in your area.

When selecting a pre-emergent product, choose a herbicide specifically labeled for crabgrass control. Many pre-emergents must be watered in after application to activate the product and create a protective barrier in the soil. Always read and follow the product label carefully to protect your lawn and ensure maximum effectiveness.

Common active ingredients for crabgrass prevention include prodiamine, pendimethalin, and dithiopyr. Dithiopyr stands out because it can also control crabgrass post-emergence up to the 1-3 tiller stage, in addition to providing pre-emergent protection when applied early.

To get rid of crabgrass that has already started to sprout in your lawn, use a post-emergent herbicide to kill actively growing weeds. For best results, post-emergent crabgrass killers should be applied early in the plant’s growth cycle, when crabgrass is small and easier to control. Be sure to read all product instructions, and in this case, use a post-emergent labeled for crabgrass control.

Post-emergent treatments are most effective when applied before mid-summer, as mature crabgrass plants become significantly harder to kill. Applications should be made when your lawn is healthy and not under drought or heat stress.

For effective post-emergent crabgrass control:

• Treat crabgrass while plants are young and actively growing.
• Use a surfactant or methylated seed oil (MSO), if recommended on the product label, to help the herbicide stick to weed leaves and absorb into the plant for better control.
• Avoid applications when temperatures exceed 85 degrees.
• Do not apply during drought conditions or when grass is stressed.
• Follow label instructions regarding mowing before and after application.
• Water the treatment area beforehand if required by the label.
• Always choose a product labeled as safe for your specific grass type.