Battling Quackgrass in a New Lawn: Why Sugar Fails and What Works

Battling Quackgrass in a New Lawn: Why Sugar Fails and What Works

You have a new lawn—50% ‘Defiance’ tall fescue, 50% quackgrass (likely from straw mulch). You applied 15 lbs sugar/1,000 sq ft. Sugar won’t work. Here’s why, and what will.

Know the Enemy

Quackgrass (Elytrigia repens) spreads by steel-strong underground rhizomes. Each piece can regenerate. It’s on Michigan’s Top 5 Most Wanted Weeds list. One plant produces ~25 seeds (viable 4 years), but rhizomes are the real threat.

The 3-Month Window

Young quackgrass takes 2–3 months to develop rhizomes. That’s your only easy-control window. After that, tilling chops rhizomes into thousands of new plants—like the German invasion of Europe.

Effective Controls

• Solarization: Clear plastic, 6–8 weeks in summer heat. Kills rhizomes and seeds.
• Steinernema kushidai nematodes: Japanese beneficial nematode—“extraordinarily lethal” to grubs and soil pests, kills in 24–48 hrs. Not yet widely sold in US; check Natural Insect Control (Canada).
• Persistent digging + mowing: Never let it seed. Dig rhizomes weekly.

Your ZIP Code Matters

Climate dictates which biocontrols establish. Provide your zip for tailored advice.

Sugar is a myth. Rhizomes are real. Act fast, act hard, and stay after it.