Why is My Lawn Yellow Jacksonville? 8 Common Causes and Fixes

You're driving through Riverside or Mandarin admiring those perfect green lawns, then you pull into your driveway and see your grass looking pale, yellowish, and sickly. What happened? Last month it looked fine.

Yellow grass is one of the most common complaints I hear from Jacksonville homeowners. The frustrating part is that "yellow grass" can have a dozen different causes, and the fix for one problem might make another problem worse. After troubleshooting hundreds of yellowing lawns across Northeast Florida, I've learned that diagnosis is 90% of the solution.

Let me walk you through the most common causes of yellow grass in Jacksonville's Zone 9a/9b climate and how to identify which problem you're dealing with.

Understanding Normal Color Variation

First, let's establish what healthy grass looks like in Jacksonville. St. Augustine—our most common turfgrass—should be a rich, dark green during the growing season (April through October). In winter, it naturally fades to lighter green or slightly yellowish-green as it goes semi-dormant. That's normal.

Bahia grass is naturally a lighter green than St. Augustine—almost apple-green. If your Bahia looks yellowish in summer, that might actually be normal for the variety.

Zoysia is typically medium to dark green depending on the variety.

If your lawn is suddenly yellower than it was last month, or yellower than your neighbors' lawns of the same species, something's wrong. Let's figure out what.

1. Nitrogen Deficiency (Most Common Cause)

This is the number one reason lawns turn yellow in Jacksonville. Grass needs nitrogen to produce chlorophyll, which makes it green. Our sandy Florida soil doesn't hold nutrients well—they wash through quickly with our frequent rain.

Symptoms:

• Uniform yellowing across the entire lawn
• Older grass blades yellower than new growth
• Grass still growing but pale
• Spreads gradually over weeks

How to confirm: Think about the last time you fertilized. If it's been more than 6-8 weeks during growing season, nitrogen deficiency is likely.

Fix: Apply a nitrogen-rich fertilizer appropriate for your grass type. For St. Augustine, use a slow-release fertilizer with analysis like 16-4-8 or similar (that first number is nitrogen).

Jacksonville lawns typically need fertilizing 4-6 times per year—more often than northern lawns because our soil doesn't hold nutrients and our growing season is longer.

Within 7-10 days of proper fertilization, you should see greening. Full recovery takes 3-4 weeks.

Prevention: Establish a regular fertilization schedule. I recommend feeding St. Augustine in March, May, July, and September at minimum. Adjust based on how your lawn responds.

2. Iron Deficiency (Iron Chlorosis)

Iron deficiency looks similar to nitrogen deficiency but has distinct characteristics. This is particularly common in Jacksonville's alkaline soil areas and during rainy periods when iron gets locked up in the soil.

Symptoms:

• Yellow grass with green veins (striped appearance)
• New growth more affected than old growth (opposite of nitrogen deficiency)
• Often appears after heavy rain or overwatering
• Can appear suddenly

How to confirm: Look closely at individual grass blades. If the veins are green but the area between veins is yellow, that's iron chlorosis.

Fix: Apply iron supplement—either granular or liquid. Liquid iron (like iron sulfate or chelated iron) provides the fastest response.

For quick greening, spray liquid iron directly on the grass. You'll see improvement in 3-5 days. For longer-term iron availability, use granular iron supplements.

Prevention: Use fertilizers that include iron (often labeled "with iron" or showing Fe in the analysis). In Jacksonville's slightly alkaline soils, iron supplements 2-3 times per year help maintain good color.

Avoid overwatering, which makes iron less available to plants.

3. Improper Watering (Too Much or Too Little)

Watering issues cause more lawn problems than anything else in Jacksonville. Both overwatering and underwatering can cause yellowing.

Underwatering symptoms:

• Yellow-brown patches
• Grass blades folded or curled
• Footprints remain visible long after walking on lawn
• Soil dry several inches deep
• Often worst in full-sun areas

In Jacksonville's sandy soil, water drains quickly. During our hot, dry spring periods (April-May before rainy season), grass can get stressed fast.

Overwatering symptoms:

• Uniform pale yellow-green color
• Soft, spongy soil
• Fungal issues often present
• Grass roots shallow (pulling up grass shows short roots)
• Often accompanied by mushrooms or algae

Jacksonville's summer rainy season (June-September) means lawns often get too much water, not too little.

How to confirm: Check soil moisture. Push a screwdriver into the soil. It should penetrate easily 6-8 inches deep if moisture is adequate. If you can't push it more than 2-3 inches, you're underwatered. If it pushes easily but water pools on the surface or soil is constantly soggy, you're overwatered.

Fix:

For underwatering: Water deeply and less frequently. St. Augustine needs about 1-1.5 inches per week total (rain plus irrigation). Water 2-3 times per week in dry periods, applying enough to wet soil 6-8 inches deep.

For overwatering: Cut back on irrigation. During Jacksonville's rainy season, you might not need to irrigate at all. Let soil dry slightly between waterings.

Prevention: Adjust irrigation based on rainfall. Use rain sensors on irrigation systems (required by code in many Jacksonville areas). Water early morning to reduce fungal issues.

4. Chinch Bugs (Serious Problem in Jacksonville)

Chinch bugs are tiny insects (1/6 inch long) that suck fluids from grass blades, causing yellowing and death. They're extremely common in Jacksonville St. Augustine lawns, especially during hot, dry weather.

Symptoms:

• Yellow patches that expand rapidly, typically in full sun areas
• Patches turn brown and grass dies
• Often starts near driveways, sidewalks, or hot spots
• You might see tiny black bugs with white wings at the edge of damaged areas
• Damage spreads in a circular pattern

How to confirm: The "float test" – Cut both ends off an empty coffee can. Push one end into the soil at the edge of a yellowing patch. Fill with water and watch for 5-10 minutes. Chinch bugs will float to the surface if present.

Look closely at grass near damaged areas early morning or evening. Chinch bugs are most visible when temperatures are moderate.

Fix: Apply insecticide labeled for chinch bugs. Options include bifenthrin, lambda-cyhalothrin, or organic alternatives like neem oil.

Severely damaged areas will need reseeding or resodding once the insects are controlled.

Prevention: Healthy, well-watered lawns resist chinch bugs better. During Jacksonville's hot dry periods, keep grass adequately watered. Avoid excessive nitrogen fertilization in summer, which makes grass more attractive to chinch bugs.

Regular monitoring catches infestations early when they're easier to treat.

5. Fungal Diseases

Jacksonville's hot, humid climate is perfect for lawn fungal diseases. Several cause yellowing.

Gray Leaf Spot (Most Common on St. Augustine)

Symptoms:

• Small yellow spots on blades that turn gray-brown
• Spots have dark borders
• Appears during hot, humid, rainy weather
• Can cause rapid lawn decline

Brown Patch

Symptoms:

• Circular yellow-brown patches 2-3 feet across
• Grass blades pull easily from stolons
• Active during warm, wet conditions
• Often has darker ring at the edge (smoke ring)

Pythium Blight

Symptoms:

• Greasy-looking yellow patches
• Appears suddenly during very humid conditions
• Grass matted and slimy
• Worst during extreme heat and humidity

How to confirm: Fungal diseases typically appear during or after prolonged wet, humid conditions. Look for characteristic patterns—spots on blades, circular patches, or greasy appearance.

Fix: Fungicides labeled for lawn fungi can control active infections. But environmental changes are equally important:

• Reduce watering frequency
• Water only early morning (never evening)
• Improve air circulation by pruning overhanging vegetation
• Mow regularly to remove infected material
• Avoid walking on infected areas when wet

Prevention: Jacksonville's humidity makes preventing fungal diseases challenging. Best practices:

• Water early morning only
• Don't water in evening
• Avoid overwatering and overfertilizing
• Ensure good drainage
• Improve air circulation around lawn

6. Dog Urine Spots

If you have dogs, those bright yellow or brown spots are probably urine damage. The high nitrogen concentration in dog urine essentially "burns" the grass.

Symptoms:

• Small circular spots (6-12 inches)
• Bright yellow or brown center with dark green ring around the edge
• Located where dogs regularly urinate
• More common with female dogs (who squat in one spot)

How to confirm: If you have dogs and the pattern matches, it's probably urine damage.

Fix: Water spots heavily immediately after dogs urinate to dilute the urine. For established spots, rake out dead grass and overseed or patch with sod.

Prevention:

• Train dogs to urinate in designated areas (mulched bed, gravel area)
• Water spots immediately after dogs urinate
• Some homeowners have success with dietary supplements that supposedly reduce urine nitrogen (ask your vet)
• Create a designated dog run area with different ground cover

In reality, most Jacksonville homeowners with dogs accept some urine damage as part of dog ownership.

7. Soil Compaction and Poor Drainage

Jacksonville's sandy soil doesn't typically have compaction issues like clay soils, but high-traffic areas can become compacted, and some properties have clay layers below the surface.

Symptoms:

• Yellow areas in high-traffic paths
• Water pools rather than soaking in
• Grass thin and struggling
• Soil feels hard

How to confirm: Push a screwdriver into affected areas. If it meets resistance at shallow depth, you have compaction.

Fix: Core aeration (pulling plugs of soil to create air channels) helps relieve compaction. For St. Augustine lawns, spring or early summer is best.

For areas with consistently poor drainage, you might need to:

• Improve grading to move water away
• Install drainage systems
• Amend soil with organic matter

Prevention: Avoid heavy traffic on wet grass. Create dedicated pathways in high-use areas.

8. Herbicide Damage

Sometimes yellowing is caused by herbicide—either intentional application that went wrong, or drift from nearby applications.

Symptoms:

• Irregular yellow patterns
• Twisting or cupping of grass blades
• Appears after recent herbicide application (yours or neighbors')
• Pattern might follow spray paths

How to confirm: Think about recent herbicide use. Did you apply weed killer? Did neighbors spray? Is the pattern consistent with drift from a spray application?

Broadleaf herbicides (2,4-D and similar) can damage St. Augustine if applied during hot weather or at excessive rates.

Fix: Stop applying herbicides. Water heavily to help flush chemicals through soil. Apply iron and nitrogen to encourage new growth.

Recovery takes weeks to months depending on severity. Severely damaged areas might need resodding.

Prevention:

• Use St. Augustine-safe herbicides
• Never apply herbicides when temperatures exceed 85°F
• Follow label rates exactly
• Avoid spraying on windy days
• Be cautious with weed-and-feed products

Diagnosing Your Specific Yellow Grass Problem

Here's a systematic approach:

Step 1: When did it start?

• Gradual over weeks → Likely nitrogen deficiency
• Sudden over days → Likely chinch bugs, fungal disease, or herbicide damage

Step 2: What's the pattern?

• Uniform across entire lawn → Nitrogen deficiency, iron deficiency, or watering issue
• Patches spreading from center → Chinch bugs or fungal disease
• Small circular spots → Dog urine or disease
• Irregular pattern → Herbicide damage or soil issues

Step 3: Look closely at grass blades

• Yellow with green veins → Iron deficiency
• Yellow with gray spots → Gray leaf spot
• Yellow and easily pulled from soil → Fungal disease or severe insect damage

Step 4: Check soil moisture

• Too dry → Underwatering
• Too wet/soggy → Overwatering or drainage problem

Step 5: Look for insects

• Tiny black bugs at damage edges → Chinch bugs
• No insects visible → Probably not insect-related

Step 6: Consider timing

• Hot, dry spring (April-May) → Often chinch bugs or water stress
• Rainy summer (June-September) → Often fungal disease or overwatering
• Any time if not fertilized recently → Nitrogen deficiency

Jacksonville-Specific Considerations

Our Sandy Soil

Nutrients wash through sandy soil quickly. Jacksonville lawns need more frequent fertilization than lawns in clay or loam soils.

Don't assume you're fertilizing enough—St. Augustine in Jacksonville's sand needs regular feeding.

Summer Rainy Season

June through September, we get afternoon thunderstorms almost daily. Your irrigation system should be adjusted or turned off entirely during this period.

Overwatering during rainy season is extremely common and causes multiple problems—yellowing, fungal diseases, shallow roots.

Chinch Bug Pressure

Jacksonville has significant chinch bug pressure. If you have St. Augustine, you WILL deal with chinch bugs eventually. Regular monitoring and quick treatment prevent extensive damage.

Water Restrictions

Many Jacksonville areas have watering restrictions (typically two days per week). This is usually adequate for established lawns if you water deeply on your allowed days.

Mixed Grass Types

Some Jacksonville properties have St. Augustine, Bahia, or other grasses in different areas. They have different nutrient needs and optimal colors. What looks yellow for St. Augustine might be normal for Bahia.

When to Call a Professional

Some situations benefit from professional diagnosis:

• You've tried the obvious fixes (fertilizer, adjusting water) without improvement
• Damage is spreading rapidly
• You suspect disease but aren't sure which one
• Large areas are affected
• You're not comfortable diagnosing the problem yourself

Lawn care professionals and extension services can do soil tests, disease identification, and provide specific treatment recommendations.

The University of Florida IFAS Extension has offices in Jacksonville and offers low-cost or free diagnostic services.

My Bottom-Line Recommendation

Start with the most common causes:

1. Fertilize if you haven't in the last 6-8 weeks during growing season
2. Check for chinch bugs if patches are expanding in hot, dry weather
3. Adjust watering based on current conditions and rainfall
4. Apply iron if grass has striped appearance

These four steps solve 80% of yellow grass problems in Jacksonville.

If you've addressed these and yellowing persists, investigate fungal diseases, herbicide damage, or soil issues.

Remember that Jacksonville's climate is challenging for lawns. Hot, humid summers, sandy soil, frequent rain, and active pests mean lawns need regular attention. The picture-perfect green lawns you see in Riverside and Avondale don't maintain themselves—they're the result of consistent care and quick response to problems.

Yellow grass is usually fixable. Identify the cause, address it appropriately, and your lawn should recover within a few weeks. The key is paying attention and catching problems early before minor yellowing becomes extensive damage.