Crabgrass Prevention and Control

Crabgrass (Digitaria sanguinalis and Digitaria ischaemum) is a summer annual — it germinates from seed in spring, grows aggressively through summer, sets seed, and dies with the first frost.

Crabgrass (Digitaria sanguinalis and Digitaria ischaemum) is a summer annual — it germinates from seed in spring, grows aggressively through summer, sets seed, and dies with the first frost. The reason it's so persistent is the seed bank it builds: one plant can produce 150,000 seeds. A lawn with a five-year history of crabgrass infestations has an enormous reservoir of viable seed in the top inch of soil that will remain a management challenge for years.

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Understanding the crabgrass lifecycle

Digitaria sanguinalis (large crabgrass) and Digitaria ischaemum (smooth crabgrass) are both summer annuals with identical management implications. Per Penn State Extension, crabgrass seed germinates when soil temperatures at 2-inch depth reach 55°F from below for several consecutive days. In most of the Northeast and Mid-Atlantic, this occurs in mid-April to early May — roughly concurrent with forsythia bloom or dogwood bloom, which are commonly used as phenological cues.

The germination window is not a single day — it extends over several weeks. Crabgrass that misses the first germination pulse due to a cold snap can germinate in later warm spells through June. A pre-emergent applied correctly maintains a barrier through this entire window.

Mature crabgrass plants produce seed by midsummer and continue through fall. Per NC State Extension TurfFiles, viable seed from a single plant can remain dormant in the soil for 3—5 years.