How do I treat Onion weed and Onion grass/Guildford grass in lawn?

🧪 Understanding the Weeds You’re Dealing With

Onion weed and onion grass / Guildford grass are some of the toughest lawn weeds in Australia because:

• They grow from a bulb which stays alive even if the top is removed.
• Pulling it out doesn’t work, the bulb snaps off and multiplies.
• Typically appears in autumn, winter and spring producing slender stems and sometimes purple flowers.
• Very difficult to mow off

Because of this, the only reliable control method is a systemic herbicide that moves into the bulb.

🌱 Why Odessa Herbicide + Wetter 600 Works

Odessa Herbicide + Wetter 600 Surfactant, contains a sulfonylurea active that is designed to:

• Translocate into the bulb/corm, killing the weed at its source.
• Provide selective control, meaning it targets the weed without damaging couch, kikuyu, or buffalo when used as directed. NOT recommended on QLD Blue Couch.
• Work on both broadleaf and grassy weeds, including Guildford grass.

The included Wetter 600 improves leaf coverage and penetration, very beneficial for waxy, upright weeds like onion weed.

✅ Best Practice Application Guide

To maximise results when using Odessa Herbicide + Wetter 600:

1. Apply When Weeds Are Actively Growing

Onion weed and Guildford grass grow strongest in autumn–winter, making this the ideal treatment window.

2. Use the Correct Mixing Rate

Follow the label exactly. Sulfonylurea herbicides work at very low rates, more is not better.

3. Add Wetter 600 into the spray mixture to assist with uptake.

4. Spray, Don’t Spot‑Pull

Manual removal leaves bulbs behind. A foliar spray is the only method that kills the underground structure.

5. Expect a Slow Kill (4–6 Weeks)

Bulb weeds die gradually as the herbicide moves into the underground storage organ.

6. Avoid Mowing 3–4 Days Before & After

This ensures maximum leaf area for herbicide uptake.

7. Re‑treat the Following Season if Needed

Deep bulbs or large infestations may require a second annual treatment.

🛑 Common Mistakes to Avoid

• Do not use hose‑on sprayers, they dilute the herbicide too much and reduce accuracy.
• Do not apply during extreme weather or frost, uptake will be poor.
• Do not blanket spray newly laid turf, wait until fully established.

🌿 Final Takeaway

Odessa Herbicide + Wetter 600 is one of the most effective homeowner accessible solutions for onion weed and Guildford grass because it targets the bulb, the part that makes these weeds so persistent. Apply during active growth, allow 4–6 weeks for results.

Mighty Goat Lawns 🐐