Controlling Dollarweed in St. Augustine Lawns: Water Management and Professional Solutions

Dollarweed (also called pennywort) thrives in overly moist conditions, making it a common nuisance in St. Augustine lawns—especially in humid regions like Southwest Florida. If atrazine applications haven't worked, the problem likely stems from cultural practices rather than herbicide failure.

Address the Root Cause: Excess Moisture

Dollarweed's extensive root system allows it to persist once established. The first step is evaluating your irrigation system. Overwatering creates ideal conditions for this weed. Contact your local extension service for precise watering recommendations—St. Augustine typically needs deep, infrequent irrigation to encourage deep rooting and discourage shallow-rooted weeds.

Understanding Atrazine Limitations

Atrazine is a restricted-use herbicide with strict application windows and annual limits. If you've already reached the maximum allowable applications, further use is illegal and ineffective. The product label specifies timing restrictions (often limited to cooler months) and maximum rates per season.

When to Call a Professional

If you've exhausted legal atrazine applications and dollarweed persists, hire a licensed lawn care professional. They have access to:

• Alternative herbicides not available to homeowners
• Precision application equipment
• Expertise in St. Augustine sensitivity—this grass is easily damaged by improper chemical applications

Integrated Management Strategy

1. Audit irrigation: Reduce frequency, increase depth; ensure proper coverage without overlap.
2. Improve drainage: Address low spots where water pools.
3. Mow correctly: Maintain St. Augustine at 3.5–4 inches to shade out weeds.
4. Fertilize appropriately: Avoid excess nitrogen, which promotes succulent growth vulnerable to weeds.

Dollarweed control is rarely achieved through herbicides alone. Long-term success requires correcting the moist conditions that favor it while using targeted chemical controls within legal limits.