Eradicating Redtop (Agrostis alba) Invasion in Cool-Season Lawn

Redtop (Agrostis gigantea/alba) is a perennial bentgrass relative that contaminates lawns via contaminated topsoil. It produces low seed heads between mowings, survives herbicides, and spreads aggressively.

Why It's Winning

• Rhizomatous + stoloniferous — spreads underground and over
• Seeds at ½" height — below mower
• Tolerates low fertility, wet, acidic conditions
• Seed bank persists 5+ years
• Standard broadleaf herbicides don't touch it

Organic Suppression Strategy (3-5 Year Commitment)

1. Build soil health: Annual compost topdress (¼") + aeration → favors desired grasses
2. Mow high (3.5-4"): Shades redtop, favors Kentucky bluegrass/fescue
3. Corn gluten meal: 20 lbs/1,000 sq ft late summer (pre-emergent on seed)
4. Overseed aggressively: TTTF + microclover each fall — competition
5. Sugar + alfalfa meal: Spring/fall — microbial boost
6. Hand-remove patches: Dig 6" deep, remove rhizomes, resod

Solarization Option (For Severe Patches)

• July-August: mow low, water deeply, clear 6-mil plastic, seal edges
• 6-8 weeks — kills seeds, rhizomes, pathogens in top 6-12"
• Replant immediately with quality seed

Chemical Option (If Organic Fails)

Mesotrione (Tenacity) — selective for bentgrass/redtop in Kentucky bluegrass/fescue. Requires precise timing, multiple apps. Professional application recommended.

Redtop arrived with 300 yds topsoil. Screen future soil deliveries. Persistence + soil building eventually shifts balance.