Crabgrass post-emergent (escapes)

Recognize it early

Young crabgrass is lighter green than the lawn, with wider, flatter blades that grow outward from a central point. It thrives in thin, short-mown, sunny patches and along paths and edges where the soil heats up. By midsummer it forms sprawling clumps and starts setting seed.

When to treat

From June through July, while the plants are small and have only a few side shoots (tillers). Young plants are much easier to kill; mature crabgrass needs repeated treatment, and seed it has already dropped will come up next year.

How

• Use a selective grassy-weed herbicide authorized for lawns in your country, and follow its label exactly.
• Spot-treat the affected patches rather than the whole lawn.
• Avoid spraying in extreme heat or on drought-stressed grass, which is more easily damaged.
• A few plants can simply be dug out by the root before they seed.

Stop it coming back

Crabgrass fills gaps. After treating, close those gaps: mow higher (see mowing height in summer), water deeply, and overseed thin areas in autumn. If it was widespread, plan a pre-emergent for next spring.