Crabgrass in Bermuda: kill it now or wait?

Crabgrass is a summer annual: it sprouts in spring, spreads through summer, drops thousands of seeds and dies at the first frost. That life cycle decides whether you should spray it or leave it alone.

Early summer: kill it

If it’s June or early July and the crabgrass is small (a few leaves, just starting to spread), a post-emergent herbicide that is labeled safe for Bermuda — quinclorac is the common one — works well. Young crabgrass dies fast and the Bermuda fills in the gap.

• Spray on a calm day with no rain for at least 24 hours
• Skip it when the lawn is drought-stressed or it’s extremely hot — read the label’s temperature limits
• Mature, clumpy crabgrass may need a second application

Late summer: usually wait

By late August, the crabgrass has already set seed. Killing it now leaves brown clumps and does nothing about the seeds already in the soil. Frost will kill it for free in a couple of months. Mow regularly so it doesn’t make more seed heads, and put your money into next spring.

The spring plan that ends it

1. Put down a pre-emergent (prodiamine or dithiopyr are common) when soil temperature holds around 55°F for several days.
2. Water it in with about half an inch of water within a few days.
3. Apply a second round 6–8 weeks later to keep the barrier through summer.
4. Keep the Bermuda thick: feed it on schedule and mow at 1–2 inches. Crabgrass needs bare soil and sunlight to get started.

Dithiopyr has a bonus: it can also knock out very young crabgrass that has already sprouted, so it’s forgiving if your timing runs a little late.