Weed Management in a New Pennsylvania Lawn: Mowing, Organic Fertilization, and Pre-Emergent Strategy

The Scenario

6-week-old lawn in PA, mowed 3×, heavy weed pressure. Homeowner wants control without harming new grass.

Rule 1: Mow High, Mow Often

• Cool-season grasses (bluegrass, rye, fescue): 3 inches.
• Mowing shades weed seeds, returns N via clippings, stresses weeds.
• Most weeds are annuals—prevent flowering/seed set, they won’t return next year.

Rule 2: Fertilize Organically

• Milorganite (slow-release, 6-2-0) – one application now.
• Blood meal, alfalfa meal – also excellent.
• University of Illinois study: even low N rates reduce broadleaf weeds and eliminate herbicide need.

Rule 3: Corn Gluten Meal Next Spring

• Apply at forsythia bloom (soil ~55°F).
• Acts as pre-emergent on germinating weed seeds.
• Decomposes to feed grass all season—no extra N needed.
• Timing critical: dry period after application for best efficacy.

Why Avoid Chemicals

Herbicides kill soil microbes → thatch buildup → more problems. “Proper mowing, watering, fertilizing develops a lawn that needs less chemicals.” – The Lawn Institute.

Start today: mow at 3", apply Milorganite, mark calendar for forsythia bloom next spring. Weeds will fade.