Kentucky Bluegrass Pre-Emergent Guide
Split spring application: first app BEFORE soil temps hit 55°F at 4-inch depth for 3-5 consecutive days, second app 6-8 weeks later. Common active ingredients: prodiamine (Barricade) or dithiopyr (Dimension). Fall pre-emergent targets Poa annua (annual bluegrass) — apply in early September when soil temps drop below 70°F. CRITICAL CONFLICT: if you plan to overseed KBG in fall, standard pre-emergents will prevent your seed from germinating. Solution: use mesotrione (Tenacity) as your fall pre-emergent — it is the ONLY pre-emergent safe to apply at seeding for KBG. Apply Tenacity at 5 oz per acre at the time of seeding, then a second app 2-3 weeks later. This controls Poa annua and broadleaf weeds while allowing KBG germination.
Frequently Asked Questions
When should I apply pre-emergent to KBG?
Apply before soil temps reach 55°F at 4-inch depth. Split the application: half rate in early spring, second half 6-8 weeks later. This extends protection through the full crabgrass window.
What about fall pre-emergent with KBG?
If overseeding in fall, use Tenacity (mesotrione) as your pre-emergent — it's the only option that won't block KBG seed germination. If not overseeding, standard pre-emergents work fine for Poa annua control.
Is Tenacity really safe for KBG seedlings?
Yes. Tenacity (mesotrione) is labeled safe for use at time of seeding on KBG and other cool-season grasses. It provides pre-emergent weed control without blocking grass seed germination. Slight temporary whitening of existing grass is normal.
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