Why Is My St. Augustine Grass Dying? A Tampa Bay Guide

St. Augustine is the most common lawn grass in Florida, and right now a lot of Tampa Bay lawns are struggling. If yours has yellow spots, brown patches or rings, here are the most likely causes and what you can do about each one.

1. It's thirsty (start here)

Tampa Bay is in a drought. Hillsborough County is limited to watering one day a week through March 31, 2027, and only between 12:01 and 4 a.m. or 8 and 11:59 p.m. Your day depends on the last number of your address (0 or 1 Monday, 2 or 3 Tuesday, 4 or 5 Wednesday, 6 or 7 Thursday, 8 or 9 Friday). The City of Tampa has its own schedule, so check yours.

Signs your grass needs water: the leaf blades fold in half, the lawn turns a blue-gray color, or your footprints stay visible after you walk on it. When you do water, UF/IFAS recommends ½ to ¾ inch at a time, which soaks the top 8 inches of soil where the roots are. Make the most of your one day rather than a light sprinkle.

2. Chinch bugs

Chinch bugs are the number one pest of St. Augustine in Florida. They suck the juice out of the grass, leaving yellow patches that turn brown and spread outward. Damage usually starts in hot, sunny spots along driveways, sidewalks and the edges of the lawn, which is why it's easy to mistake for drought.

The clue: if watering doesn't help and the brown area keeps growing, check for bugs. Cut both ends off a can, push it 2 to 3 inches into the soil where brown grass meets green, and fill it with water. Chinch bugs float to the top within about 5 minutes.

Chinch bugs in our area have become resistant to some common insecticides, so treatment is a job for a licensed pest control company.

3. Large patch (the "circles" fungus)

If you see round patches, often a foot or more across, with a yellow or orange border, it's probably large patch. It shows up when temperatures drop below 80 degrees, usually November through May, and loves grass that stays wet. Pull a blade at the edge of the patch: if it slides right out and the base is dark and rotten, that's large patch.

What helps: water only when the grass needs it (early morning, never in the evening before a cool night), and don't put down extra nitrogen in the fall. A fungicide may be needed if it keeps spreading.

4. Mowing too short, or with dull blades

This one is easy to fix. Standard St. Augustine (Floratam, Bitterblue and similar) should be cut at 3½ to 4 inches. Mowing lower stresses the grass, keeps the roots shallow and invites bugs and disease. Never cut off more than a third of the blade at once.

Dull mower blades shred the grass instead of cutting it, which gives the whole lawn a brownish look. UF/IFAS recommends sharpening blades monthly during the growing season.

5. Other things to rule out

• Gray leaf spot: small gray or tan spots with brown edges on the blades, mostly during the summer rainy season.
• Take-all root rot: yellow, thinning patches where the roots are short and black.
• Nematodes: thin, weak grass that's slow to recover after rain, often with weeds moving in.
• Too much shade: Floratam needs at least 6 hours of sun a day.
• New sod: newly laid sod needs extra water while it roots. Hillsborough County allows new lawns to be watered any day (during the allowed hours) for the first 30 days.

A note on fertilizer

In Hillsborough County and the City of Tampa, fertilizer with nitrogen or phosphorus can't be used from June 1 through September 30. Iron-only "summer blends" are allowed. Too much nitrogen actually feeds large patch and chinch bugs, so more fertilizer isn't the fix for a sick lawn.

Still not sure?

The UF/IFAS Extension office in Hillsborough County can help identify lawn problems. For bugs or fungus, call a licensed pest control company.

Sources: UF/IFAS Extension (St. Augustinegrass for Florida Lawns, Large Patch, Southern Chinch Bug), Hillsborough County and City of Tampa fertilizer ordinances, Hillsborough County watering restrictions (September 2026).

How High Should I Mow My Lawn? A Tampa Bay Q&A

The right mowing height depends on your type of grass. Cutting too low is one of the most common reasons Florida lawns get thin, weedy and stressed. Here are the heights the University of Florida recommends, plus answers to the questions we hear most.

How high should I cut my grass?

It depends on the grass. These are the UF/IFAS recommended heights for Florida home lawns:

Grass type	Mowing height
St. Augustine, standard Floratam, Bitterblue, Classic	3½ to 4 in.
St. Augustine, dwarf Seville, Delmar, Captiva	2 to 2½ in.
Bahia	3 to 4 in.
Zoysia, coarse types Empire, JaMur	2 to 2½ in.
Zoysia, fine types Emerald, Zeon	under 2 in.
Centipede	1½ to 2 in.
Bermuda	1 to 2 in.
Seashore paspalum	1 to 2 in.

Most lawns in the Tampa Bay area are Floratam St. Augustine or bahia, so for most homes the answer is 3½ to 4 inches.

Isn't shorter better? Then I don't have to mow as often.

No. Cutting below the recommended height stresses the grass, keeps the roots shallow and makes the lawn more likely to get bugs, disease, weeds and drought damage. Taller grass grows deeper roots, which helps it handle our heat and the one-day-a-week watering limit.

How do I know what kind of grass I have?

• St. Augustine: wide, flat blades with a rounded tip, and thick runners that creep along the top of the ground.
• Bahia: tougher, more open grass that sends up tall, V-shaped seed heads in summer.
• Zoysia: dense, stiff blades that feel prickly; it makes a thick carpet.
• Bermuda: very fine blades that grow fast and creep into flower beds.
• Centipede: light green, medium blades; low-growing and slow.

Not sure? Ask us when we come out for an estimate, or take a sample to the UF/IFAS Extension office in Hillsborough County.

How much should I cut off at one time?

Never more than one-third of the blade. For example, if you keep St. Augustine at 4 inches, mow it before it gets taller than about 6 inches.

How often should I mow?

Mow by how fast the grass grows, not by the calendar. In the Tampa Bay area, St. Augustine usually needs mowing about once a week in the summer growing season and less often in the cooler months. Bahia can often go a little longer between mowings. Bermuda grows fastest and may need mowing every few days to keep it short.

My grass got too tall. Should I cut it all the way down?

No. Raise the mower, take off no more than a third, then bring it back down to the normal height over the next few mowings. Cutting it all at once scalps the lawn and leaves brown, stressed patches.

Should I mow higher during a drought or in the shade?

Yes. UF/IFAS recommends raising the mowing height when the grass is stressed by dry weather or growing in shade. The extra leaf helps it hold moisture and catch more light.

Should I bag the clippings?

Usually not. When the lawn is mowed at the right height and often enough, leaving clippings on the lawn returns nutrients to the soil and does not cause thatch. If they clump up, spread them out or pick them up.

Does it matter if my mower blades are dull?

Yes. Dull blades tear the grass instead of cutting it, which gives the whole lawn a brownish look and can invite disease. UF/IFAS recommends sharpening blades about once a month during the growing season.

Sources: UF/IFAS Extension (Mowing Your Florida Lawn; St. Augustinegrass for Florida Lawns; Zoysiagrass for Florida Lawns; Homeowner Best Management Practices for the Home Lawn).