When to fertilize Kentucky bluegrass in Wisconsin?
By LawnYear editorial team · Published · Updated Windows are read from the extension publications listed under Sources; the dates are approximate.
The answer
The fertilizing windows for Kentucky bluegrass in Wisconsin are Sep 1 to Sep 15 and May 20 to Jun 10, per University of Wisconsin-Madison Division of Extension (2022 and 2025). Early fall, September 1 to 15, is the key nitrogen time for all lawns: about 1 lb per 1,000 sq ft of controlled-release nitrogen. Avoid mid-fall nitrogen. A3435 adds that no application should exceed 1 lb of nitrogen per 1,000 sq ft. Medium and high maintenance lawns get nitrogen in late May to early June, around Memorial Day (this site's reading): 1 lb per 1,000 sq ft in full sun and 1/2 lb in shade. The calendar says to wait until the second mowing in spring.
Full calendar: Wisconsin 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 Wisconsin windows for Kentucky bluegrass
The Wisconsin calendar on this site lists seeding Aug 20 to Sep 10 and Apr 20 to May 10, fertilizing Sep 1 to Sep 15 and May 20 to Jun 10 and watering Jun 1 to Aug 31 for Kentucky bluegrass.
Where the dates come from
University of Wisconsin-Madison Division of Extension: Wisconsin Lawn Care Calendar (2025); spring, summer and fall practices for cool-season grasses. Read on 2026-10-30. University of Wisconsin-Madison Division of Extension: A3435, Lawn Maintenance (2022); fertilization periods and rates by maintenance level, and a limit of 1 lb of nitrogen per application. Read on 2026-10-30.
What to check for Wisconsin
The fertilizing dates for Kentucky bluegrass above (Sep 1 to Sep 15 and May 20 to Jun 10) apply to Wisconsin as a whole, so the north and south of the state are not told apart.
Other grasses in Wisconsin
For tall fescue, perennial ryegrass and fine fescue, the Wisconsin calendar gives Sep 1 to Sep 15 and May 20 to Jun 10 for fertilizing.
Fertilizing Kentucky bluegrass in other states
- Virginia: Aug 15 to Oct 31 and Mar 1 to May 31, per Virginia Cooperative Extension (Virginia Tech), 2025.
- Pennsylvania: Apr 15 to May 31 and Aug 15 to Oct 15, per Penn State Extension.
- Ohio: Apr 1 to May 31 and Oct 1 to Nov 30, per Ohio State University Extension, Lake County (2007).
- Missouri: Apr 1 to Apr 30 and Sep 1 to Oct 31, per University of Missouri (Integrated Pest Management), 2015.
- Kentucky: Oct 1 to Nov 30, per University of Kentucky Cooperative Extension Service (2014).
- Indiana: May 1 to May 31, Sep 1 to Sep 30 and Nov 1 to Nov 30, per Purdue University Cooperative Extension Service (1998).
- New Jersey: Aug 15 to Sep 30 and Nov 1 to Nov 30, per Rutgers Cooperative Extension (NJAES), 2023.