Organic Johnson Grass Control: Sugar Trials and Corn Gluten Meal

Johnson grass (Sorghum halepense) is a perennial rhizomatous weed. Sugar shows promise in research; corn gluten meal is a proven pre-emergent. Here's how to test both.

Sugar Method (Experimental)

• Based on Charles Sturt University trials: sugar feeds soil microbes that temporarily suppress annual weeds.
• Test protocol: 10×10 ft plot. Dissolve ½ cup granulated sugar per gallon warm water. Spray every 3 months for 2 years.
• Critical: No chemical herbicides on test plot—they negate the microbial effect.
• Monitor and document.

Corn Gluten Meal (Proven)

• Natural pre-emergent: inhibits root formation on germinating seeds.
• Apply at 20 lbs/1,000 sq ft in early spring (before soil hits 55°F) and fall.
• Also provides ~10% nitrogen.
• Vendors & details: UW Extension corn gluten guide.

Integrated Approach

1. Mow high (3–4") to shade out Johnson grass.
2. Apply corn gluten meal on schedule.
3. Test sugar on a dedicated plot.
4. Hand-dig rhizomes persistently.
5. Overseed with competitive grass (tall fescue, zoysia).

Johnson grass demands persistence. Corn gluten meal is your reliable tool; sugar is a worthy experiment. Document everything.