The Best Methods to Control Southern Crabgrass

Pre-emergent Herbicide

• Spray a pre-emergent herbicide evenly over your yard to prevent southern crabgrass seeds from germinating in the spring. Southern crabgrass seeds germinate when the soil temperatures rise to 53 degrees Fahrenheit at a soil depth of 4 inches, according to Mississippi State University. Check your soil temperature after the last frost with a soil thermometer. Make sure that you apply the pre-emergent herbicide before the soil temperatures reach 53 degrees. Water the pre-emergent herbicide into the lawn.

Post-emergent Herbicide

• Apply post-emergent herbicide throughout the growing season when you see southern crabgrass pop up in the yard. Typically, gardeners will still see some crabgrass in the lawn even after using pre-emergent herbicide. Avoid mowing the lawn for two days prior and after spraying post-emergent herbicide. Choose a day that is free of rain for 24 hours, because the herbicide will wash off of the crabgrass if used on a rainy day. Use a post-emergent herbicide that will not harm your grass. You may need to reapply the post-emergent spray throughout the growing season. Refrain from using the spray around ornamental plants or seedlings, because the spray may harm them.

Broad Spectrum Herbicide

• You can treat southern crabgrass growing next to ornamental plants and seedlings with a broad-spectrum herbicide. Dip a small paintbrush into a herbicide that contains glyphosate. Glyphosate kills anything it comes into contact with, so be careful using it around other plants. Paint the herbicide on the blades of the southern crabgrass. Pick a dry day in order for the chemicals to become absorbed into the blades. Reapply the herbicide in a few days to any living southern crabgrass.

Digging

• For gardeners who don't want to use herbicides on the lawn, southern crabgrass can be removed by digging. However, gardeners must be digging continually to manage its populations in the yard. Press a shovel a few inches from the base of the weed and at a depth of at least 6 inches. Push the root system and plant up through the soil. Bag the debris and dispose of it.