When to apply pre-emergent

Spring applications target summer annual weeds like crabgrass and goosegrass. Fall applications target winter annual weeds like annual bluegrass, chickweed, henbit, and other cool-season germinators. A single spring application will not prevent every weed all year.

Purdue Extension describes crabgrass as a summer annual that germinates around 60 degrees Fahrenheit. Apply spring pre-emergent before the germination window, with enough time for rainfall or irrigation to move the product into the upper soil layer.

Check your current soil temperature before applying.

Most pre-emergent herbicides can also prevent desirable grass seed from establishing. If you recently seeded or plan to seed, read the label carefully and choose a product that fits that situation. Purdue notes siduron is an exception for some cool-season seedings, but it is not a season-long solution.

Common active ingredients include prodiamine, dithiopyr, pendimethalin, and dimension-style products. Use the Price Board to compare pre-emergent options after you confirm grass safety, target weeds, reseeding interval, and label rate.