How Tall to Mow St. Augustine Grass (and How Often)

Why St. Augustine wants to be tall

St. Augustine has wide leaves and grows from runners that sit right at the soil surface. Taller leaves mean more surface to collect sunlight, deeper roots, shaded soil that holds moisture longer, and a dense canopy that crowds out weeds. Cut it short and you lose all of that at once.

Most mowers' highest setting lands right around 4 inches, which is a good place to leave it. Set it once and stop adjusting.

The one-third rule

Never remove more than a third of the leaf in a single mowing. At a 4-inch height, that means mowing before the lawn gets much past 6 inches.

Here's why it shows: the lower part of each blade gets less sun than the top, so it's lighter in color. Take off too much at once and you expose that pale lower section. That's why a lawn that went too long between mowings looks yellow right after it's cut.

How often to mow

Because it's kept tall, St. Augustine needs mowing more often than people expect: at least weekly through the growing season, sometimes more in late spring when growth peaks. In the fall, growth slows and you can mow only as needed. Once it goes dormant, put the mower away.

Scalping: the most expensive mowing mistake

Scalping means cutting so low you hit the runners and expose bare soil. In St. Augustine, it can set the lawn back for weeks. It stresses the grass, invites weeds into the gaps, and in summer heat it can kill thin areas outright. Common causes:

• Dropping the mower height "to stretch time between mowings"
• Uneven ground, where the deck dips into low spots
• Letting the lawn get way too tall and then cutting it all at once

If the lawn gets overgrown, bring it down in two or three mowings a few days apart instead of one.

Mulch, don't bag

Use the mulching setting. The mower chops clippings into small pieces that break down quickly and return nutrients to the soil. Mulched clippings don't cause thatch buildup on their own. The exception is a lawn showing active fungus, where you may want to bag clippings from the affected area so you don't spread it.

Keep the blade sharp

A dull blade tears the leaf tips and leaves them brown. Sharpen it at least twice a season. I use a blade removal tool to get the blade off and a balancer to check it before it goes back on. Here's how to sharpen a mower blade.

Common questions

What is the best mowing height for St. Augustine grass?

3½ to 4 inches for standard varieties like Floratam and Raleigh, and never below 3. Dwarf types like Seville are mowed at 2 to 2½ inches.

Can you cut St. Augustine grass short?

Cutting it short, or scalping it, is one of the most damaging things you can do. It weakens the grass, invites weeds, and slows recovery. Lower it gradually if you must, and never remove more than one-third of the blade at once.

How often should I mow St. Augustine?

At least once a week during the growing season, often enough that you never cut off more than one-third of the blade.