Posted on June 24, 2026

If you've invested in a beautiful St. Augustine lawn, few things are more frustrating than seeing weeds take over. Whether it's dollarweed, crabgrass, clover, spurge, or sedge, weeds compete with your grass for water, nutrients, and sunlight while making your lawn look neglected.

The good news is that most weed problems can be controlled once you understand why they're appearing in the first place.

Why Do Weeds Grow in St. Augustine Grass?

Many homeowners assume weeds are the problem. In reality, weeds are usually a symptom of a lawn issue.

Weeds thrive when St. Augustine grass becomes thin, stressed, or damaged. Common causes include:

• Improper mowing height
• Overwatering
• Underwatering
• Poor soil health
• Insect damage
• Disease problems
• Shade stress
• Nutrient deficiencies

A thick, healthy St. Augustine lawn is your best defense against weeds.

Common Weeds Found in Florida St. Augustine Lawns

• Dollarweed

Dollarweed is one of the most common weeds found throughout Melbourne, Satellite Beach, Indialantic, and Melbourne Beach. It has round leaves that resemble silver dollars.

Dollarweed typically indicates excessive moisture in the lawn.

• Crabgrass

Crabgrass spreads quickly during the summer months and often appears in thin or damaged areas of the lawn.

• Florida Snow (Mexican Clover)

Many homeowners mistake this invasive weed for a flowering groundcover. It spreads rapidly and can quickly dominate a lawn if left untreated.

• Nutsedge

Often called "nutgrass," nutsedge grows faster than St. Augustine grass and stands taller than the surrounding lawn. It is especially common in wet areas.

• Spurge

Spurge grows low to the ground and forms dense mats that can choke out healthy turfgrass.

The Best Way to Eliminate Weeds

1. Mow Your St. Augustine Grass Higher

One of the biggest mistakes homeowners make is cutting St. Augustine grass too short.

For most lawns in Brevard County, St. Augustine should be maintained between 3.5 and 4 inches tall.

Taller grass:

• Shades weed seeds
• Develops deeper roots
• Retains moisture better
• Creates a thicker turf canopy

2. Water Properly

Overwatering encourages many common Florida weeds.

Instead of watering every day, water deeply and less frequently. Most established St. Augustine lawns need about 1 inch of water per week, including rainfall.

Signs of overwatering include:

• Mushy soil
• Dollarweed outbreaks
• Fungus problems
• Excessive weed growth

3. Fertilize Correctly

A healthy lawn naturally crowds out weeds.

Proper fertilization helps St. Augustine grow thicker and recover from stress more quickly. Always follow Florida fertilizer regulations and avoid over-fertilizing.

4. Use Pre-Emergent Weed Control

The easiest weed to kill is the one that never sprouts.

Pre-emergent herbicides create a barrier that prevents many weed seeds from germinating.

For Florida lawns, pre-emergent applications are typically most effective:

• Early spring
• Early fall

Timing is critical.

5. Spot-Treat Existing Weeds

Not all weed killers are safe for St. Augustine grass.

Using the wrong product can damage or kill your lawn.

Always read the label carefully and verify that the product is specifically approved for use on St. Augustine turf before applying.

6. Improve Thin Areas

Weeds love bare spots.

If portions of your lawn are struggling because of shade, irrigation issues, insects, or disease, those underlying problems must be corrected or the weeds will continue returning.

Why Weed Spraying Alone Often Fails

Many homeowners spend hundreds of dollars on weed killers every year only to see the same weeds return.

That's because herbicides only treat the symptom.

If the lawn remains thin, stressed, or unhealthy, new weeds will simply move in to take their place.

Long-term weed control comes from:

• Proper mowing
• Proper watering
• Healthy soil
• Correct fertilization
• Consistent lawn maintenance

Final Thoughts

The most effective way to get rid of weeds in a St. Augustine lawn is to focus on improving the health of the grass itself. While herbicides can help control existing weeds, they rarely solve the underlying conditions that allowed the weeds to become established.

By mowing at the proper height, watering correctly, fertilizing appropriately, and addressing thin or stressed areas, homeowners can create a thicker lawn that naturally suppresses many common Florida weeds.

Remember, weeds are often a sign that your lawn is trying to tell you something. Identifying and correcting the root cause will provide far better long-term results than repeatedly treating the symptoms.