Best Mowing Height for St Augustine Grass

8 min read · by Laura Kessler · Updated November 11, 2026

The best mowing height for St Augustine grass is about 2.5 to 3 inches, according to LSU AgCenter. Clemson and Texas A&M AgriLife give a wider 2.5 to 4 inch range, so this guide shows where the sources agree, when to cut higher, and how often to mow.

The best mowing height for St Augustine grass: where sources agree

Extension sources give different numbers for St Augustine grass, so the sensible choice is the band where they overlap. The table lists each figure as the source states it, including UC’s split between the mower setting and the point at which you mow again.

Clemson, LSU and AgriLife all include 2.5 inches in their figures. The UC mower setting is lower, so if you want the grass near 2 inches, the UC Healthy Lawns guidance on warm-season mowing is the closer match. Our reading is that 2.5 inches is the best mowing height for St Augustine grass to start from, because it is the one figure inside the Clemson, LSU and AgriLife ranges.

When to cut St Augustine grass higher

Cut higher than the best mowing height for St Augustine grass when shade, heat, drought or a new lawn puts the grass under stress. A taller blade gives the grass more leaf area to make food.

• Shade: Clemson says shaded grass “needs to be kept at the highest recommended height.”
• Summer heat and drought: Clemson notes that a higher height helps the grass photosynthesize more and improves drought tolerance during hotter, drier months.
• New lawns and stress: UC advises cutting on the higher end of the range for new turf and for turf stressed by drought, heat, traffic, shade or pests.

For a freshly laid lawn, see when to mow new sod. Our reading is that a higher setting through summer, then a gradual drop in fall as growth slows, is the most forgiving pattern for most homeowners. Our notes on the mowing height for shade grass and on mowing a lawn in heat and drought cover those two stress cases.

How often to mow St Augustine grass

Mow often enough that no single cut removes more than one-third of the blade height, the one-third rule, which keeps the lawn at a steady height. Clemson states the rule as “remove no more than one-third of the grass height at any one mowing,” and LSU calls it a general guideline whose benefit comes mostly from mowing regularly.

Regular mowing is how you hold the target height without taking too much leaf off at once. AgriLife explains the reason: frequent mowing keeps the growing point near the soil surface, while a lawn allowed to get shaggy lifts it, so one hard cut can remove the growing point along with the clippings.

LSU says homeowners may mow on average once a week, or three to four times a month, during the active growing season. UC says to mow frequently in spring and summer, and to mow less or not at all as growth slows and the grass goes dormant in fall and winter. AgriLife adds a simple check: if piles of clippings remain after each mowing, the lawn is being mowed too infrequently. The LSU AgCenter one-third mowing rule explains the reasoning behind this schedule.

Applying the one-third rule to LSU’s range gives a simple trigger for each setting. Our arithmetic:

Clemson also advises that if grass gets too tall between mowings, you should raise the mowing height and then lower it gradually to the recommended height, rather than cutting it all at once.

Setting a robot mower for St Augustine grass

A robot mower can hold the best mowing height for St Augustine grass if its lowest setting is 2.5 inches or lower and it runs often enough to follow the one-third rule. Our guide to robot mowers for St Augustine grass covers the rest. AgriLife says varieties that need a height at or below one inch cannot be cut well with a rotary mower, so St Augustine at 2.5 inches is not in that group. The steps below are our reading of the extension guidance, because these guides were written for push and ride-on mowers.

1. Check the lowest setting first. Compare the model’s cutting height range with 2.5 to 3 inches. A mower that cannot go that low will keep the grass taller than the extension ranges suggest.
2. Start near the top of the band. Begin around 3 inches, then lower the setting one step at a time over several weeks.
3. Run often in peak season. A mower that runs most days removes only a little blade each time, which is how the one-third rule is kept without measuring.
4. Raise the setting in shade and stress. Move up one step in shaded zones and during heat or drought, as Clemson and UC advise.
5. Check after a growth spurt. If the grass has grown past the one-third limit between runs, raise the height first, then lower it gradually.

Common St Augustine mowing mistakes

Most mowing problems come from removing too much blade at once, cutting too low for the conditions, or running dull blades. Each mistake undoes a good cut, and each is easy to avoid once you know the rule behind it.

• Waiting too long between mowings. Letting the grass grow well past the one-third limit forces a hard cut that stresses the lawn, and AgriLife’s clipping check will show it.
• Cutting low in shade. Clemson advises the highest recommended height for shaded St Augustine, not the lowest.
• Dropping the setting too fast. Our reading is that cutting much lower than the one-third rule allows removes too much green leaf at once, which is how scalping happens.
• Mowing over bumps and ruts. AgriLife advises evaluating the lawn for high spots, low spots and ruts to decrease scalping, and leveling them is part of the fix.
• Running dull blades. AgriLife says dull blades thrash the grass tops, leaving ragged, straw-colored tips that invite fungal pathogens. It advises having blades sharpened at least once a year.
• Skipping higher cuts in summer. Clemson links a higher height to better drought tolerance during the hottest months.

Treat the best mowing height for St Augustine grass as a starting point rather than a fixed setting. Begin at 2.5 to 3 inches, raise the setting when stress shows up, and let the one-third rule decide how often the mower runs.

Frequently asked questions

Sources

• UC Healthy Lawns: Mowing warm-season grasses (UC IPM): mower setting and mow-when heights for St Augustine grass, and advice to cut higher for stress.
• Mowing Lawns, HGIC Factsheet 1205 (Clemson Cooperative Extension): St Augustine height range, the one-third rule and mowing frequency.
• Mowing Height Matters (Clemson Cooperative Extension HGIC): higher cuts for shade and summer stress.
• The One-Third Mowing Rule (LSU AgCenter): St Augustine height range, the one-third guideline and weekly mowing guidance.
• Mowing (Texas A&M AgriLife Extension, 2026 PDF): optimal and range mowing heights by variety, the one-third rule, growing point, scalping, and blade sharpening.

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