How to Get Rid of Dollar Weed in a Florida Lawn

Dollar weed — also called pennywort — is one of the most recognizable weeds in Florida lawns. Its round, shiny leaves look like small lily pads. Once it gets established, it spreads aggressively. The good news: it tells you exactly what is wrong with your lawn conditions.

Why Dollar Weed Takes Over

Dollar weed is almost always a symptom of overwatering. It thrives in consistently wet, soggy soil. If your irrigation runs every day, or if you have poor drainage, dollar weed will find those spots and fill them in. Other contributors: low-cut grass, compacted soil, and shaded areas where grass struggles.

Step 1: Fix the Watering

Before you spray anything, reduce irrigation. St. Augustine grass needs about 3/4 inch of water per week — not per day. Install a rain sensor if you do not have one. During St. Pete's rainy season (June–September), your irrigation should barely run at all. Dollar weed will struggle once the soil stops staying saturated.

Step 2: Mow Higher

St. Augustine grass mowed at 3.5–4 inches crowds out dollar weed naturally by shading the soil. If you are mowing at 2 inches, you are giving dollar weed exactly what it needs: sunlight and space. Raise your mower deck — this single change combined with reduced watering will slow dollar weed spread significantly.

Step 3: Spot-Treat With Herbicide

For existing dollar weed, post-emergent herbicides are needed. Products containing atrazine are commonly used on St. Augustine lawns and are effective on dollar weed. Alternatives with metsulfuron or 2,4-D can also work — verify they are labeled safe for St. Augustine before applying.

Follow label directions. Most herbicides require dry conditions for 24–48 hours after application to be effective. Some herbicide applications in Florida may require a licensed applicator.

Preventing Dollar Weed From Coming Back

• Water deeply and infrequently, not daily
• Mow St. Augustine at 3.5–4 inches year-round
• Fertilize on schedule so grass grows thick and competitive
• Improve drainage in problem areas if possible
• Address bare or thin spots — dollar weed fills gaps fast