When to apply crabgrass preventer in Pennsylvania?
By LawnYear editorial team · Published · Updated Windows are read from the extension publications listed under Sources; the dates are approximate.
The answer
Preemergent weed control for Kentucky bluegrass in Pennsylvania runs from Mar 15 to May 15, per Penn State Extension. Preemergence herbicide for crabgrass in early to mid-spring: March 15 to April 15 in southeastern Pennsylvania, April 1 to May 1 in other areas, April 15 to May 15 in the northern tier and high-altitude counties. The union is shown; use your area's window.
Full calendar: Pennsylvania lawn care calendar · Kentucky bluegrass in other states · Lawn schedule by ZIP
Approximate dates for your state. Check with your local cooperative extension office before you act.
All Pennsylvania windows for Kentucky bluegrass
The Pennsylvania calendar on this site lists seeding Aug 15 to Oct 15, fertilizing Apr 15 to May 31 and Aug 15 to Oct 15 and weed control Mar 15 to May 15 for Kentucky bluegrass.
Where the dates come from
Penn State Extension: Lawn Management Through the Seasons. Read on 2026-10-29.
What to check for Pennsylvania
The weed control dates for Kentucky bluegrass above (Mar 15 to May 15) apply to Pennsylvania as a whole, so the north and south of the state are not told apart.
Other grasses in Pennsylvania
For perennial ryegrass, fine fescue and tall fescue, the Pennsylvania calendar gives Mar 15 to May 15 for weed control.
Weed control Kentucky bluegrass in other states
- Virginia: Mar 1 to Apr 30 and Aug 15 to Sep 15, per Virginia Cooperative Extension (Virginia Tech), 2025.
- Ohio: Apr 1 to Apr 25, per Ohio State University Extension, Lake County (2007).
- Kentucky: Apr 1 to Apr 30, per University of Kentucky Cooperative Extension Service (2014).
- Indiana: Apr 1 to Apr 30 and Oct 1 to Oct 31, per Purdue University Cooperative Extension Service (1998).
- New Jersey: Apr 1 to Apr 30 and Jun 1 to Jun 15, per Rutgers Cooperative Extension (NJAES), 2019.