MANHATTAN, Kan. — In many landscapes, crabgrass is considered an ‘opportunistic’ plant. Given the chance to take over thin or bare lawns, it is a more-than-willing intruder.
Crabgrass typically grows in ungainly clumps, crowding out more desirable and aesthetically pleasing grasses like the fescues, Bermuda and zoysia.
Ward Upham, a K-State Research and Extension specialist in horticulture, said the best time to rid home lawns of crabgrass is mid- to late-April, “though early April would be more appropriate for southern Kansas,” he said.
“For most of Kansas, crabgrass typically begins to germinate around May 1 or a little later,” Upham said. “April 15 is normally a good target date for applying preventer for most of Kansas because it gives active ingredients time to evenly disperse in the soil before crabgrass germination starts.”
Crabgrass preventers, he added, are just as their name suggests – they prevent the young plant from emerging. “With few exceptions, they have no effect on existing crabgrass plants, so they must be applied before germination,” Upham said.
Most crabgrass preventers are ineffective after 60 days, Upham noted, so applying the product at the right time is important.
“You can base timing of your application on the bloom of ornamental plants, such as the Eastern Redbud tree,” Upham said. “When the trees in your area reach full bloom, apply crabgrass preventer. This practice is better than using a calendar date as it compensates for location and whether we have an early spring.”
Depending on the product used, a follow-up application may be needed. Dimension and Barricade are the only two products that give season-long control of crabgrass from a single application, and in fact, can be applied earlier than April 15, according to Upham.
“We recommend crabgrass preventers be applied before fertilizer so that the grass isn’t encouraged to put on too much growth too early,” Upham said. “However, it may be difficult to find products that contain pre-emergents without fertilizer.”
A list of products recommended by K-State is available in the weekly Horticulture Newsletter, published by the university’s Department of Horticulture and Natural Resources. Upham is a regular contributor to that online publication.
— Pat Melgares, K-State Research and Extension
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