When to apply crabgrass preventer in Indiana?
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 Indiana runs from Apr 1 to Apr 30 and from Oct 1 to Oct 31, per Purdue University Cooperative Extension Service (1998). High and medium maintenance: a preemergence herbicide in April if crabgrass has been a problem. Use a product with little or no nitrogen, in slow-release form, and avoid more than 0.75 lb N per 1,000 sq ft. Whole month shown. Control dandelions and other broadleaf weeds in October, when spot or blanket broadleaf herbicide applications are most effective.
Full calendar: Indiana 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 Indiana windows for Kentucky bluegrass
The Indiana calendar on this site lists seeding Aug 15 to Sep 15, fertilizing May 1 to May 31, Sep 1 to Sep 30 and Nov 1 to Nov 30, weed control Apr 1 to Apr 30 and Oct 1 to Oct 31, mowing Apr 1 to Nov 30 at 2.5 to 3.5 in and watering Jun 1 to Aug 31 for Kentucky bluegrass.
Where the dates come from
Purdue University Cooperative Extension Service: AY-27, Maintenance Calendar for Indiana Lawns (1998); month-by-month calendar for cool-season grasses at high, medium and low maintenance levels. Read on 2026-10-30.
What to check for Indiana
The weed control dates for Kentucky bluegrass above (Apr 1 to Apr 30 and Oct 1 to Oct 31) apply to Indiana as a whole, so the north and south of the state are not told apart. Where the source names only a month, the window runs from the first to the last day of that month.
Other grasses in Indiana
For tall fescue, perennial ryegrass and fine fescue, the Indiana calendar gives Apr 1 to Apr 30 and Oct 1 to Oct 31 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.
- Pennsylvania: Mar 15 to May 15, per Penn State Extension.
- 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).
- New Jersey: Apr 1 to Apr 30 and Jun 1 to Jun 15, per Rutgers Cooperative Extension (NJAES), 2019.