Should you cut your grass short before winter in San Antonio?

No. In San Antonio, keep mowing at your normal height until the grass stops growing. Cutting the lawn short before winter is advice from places where snow sits on the grass for months, and here it only weakens St. Augustine and Bermuda right before the cold.

Where does the “cut it short for winter” advice come from?

From up north. The University of Minnesota’s turf program says a short last cut was suggested in the past as a way to reduce spring damage from snow molds and voles. Those are problems that happen under snow.

Even there, the advice has changed. The same program now says to keep the lawn at the same height you’ve had in the fall, because cutting too short stresses the grass more than the snow mold would.

We don’t have the snow. The San Antonio airport averages 0.2 inches of snow a year. So the one reason to go short doesn’t apply here, and the cost of going short still does.

What happens if you cut it short anyway?

You take away the part of the plant that feeds it. Texas A&M AgriLife says the green leaf is where the grass makes its food, and lawns mowed too low make and store less of it and handle stress worse. Winter is stress. That’s a bad time to cut into its reserves.

You also open the door for winter weeds. AgriLife says scalping exposes the soil to sunlight, which helps weeds come up and grow. Winter weeds like henbit sprout in early fall and grow through fall and winter, so bare soil in October is an invitation.

And shorter grass means shallower roots. AgriLife recommends keeping your lawn at the higher end of its range, because a taller cut supports deeper, stronger roots.

How high should the last mows be?

The same as your other fall mows. These are the settings from the Texas A&M AgriLife office in Bexar County:

Grass	Mower setting
St. Augustine	3 inches
Common Bermuda	1 1/2 inches
Hybrid Bermuda	1 inch
Zoysia	2 inches

If you raised the mower for summer, coming back to the normal setting is fine. The Bexar County chart puts St. Augustine at 3 inches, going up to 4 in hot summer, so a lawn that spent August at 4 inches can come back to 3. Do it over a few mows. AgriLife’s rule is to never take off more than a third of the grass in one cut.

Just don’t go below the normal setting. For St. Augustine, AgriLife tells homeowners to set the mower at the highest setting or one step below and leave it there.

Is St. Augustine different from Bermuda?

Yes, and it matters most for St. Augustine. Bermuda has stems under the ground that it can grow back from. St. Augustine doesn’t. It spreads only by runners on top of the soil, so AgriLife says damage to the top of the plant can have a more lasting impact than it would on Bermuda or zoysia.

That’s also why AgriLife says scalping in spring is generally not recommended for St. Augustine lawns. If it’s a bad idea in spring, when the grass is about to grow, it’s a worse one in fall, when the grass is about to stop.

When do you stop mowing?

When the grass stops growing, not on a set date. AgriLife says it’s unnecessary to mow warm-season grass once it’s dormant.

You may still need a mow or two after that. AgriLife says regular mowing while winter weeds are growing helps keep them in check, and cutting off their flowers and seed heads keeps them from spreading. We cover the timing in when grass goes dormant in San Antonio.

In San Antonio

Our fall is long. At the airport, the first freeze comes by Nov. 28 in half of years, and in one year out of ten it holds off until Dec. 22 or later. That means your lawn can keep growing for weeks after lawns up north have shut down. A “last cut of the year” in October is too early here.

St. Augustine is the grass to be most careful with. It takes a short cut the hardest, and AgriLife warns that it can suffer winter kill in some parts of Texas. Don’t send it into a freeze already stressed. Here is how to get your yard ready for a freeze.

Live oaks and other trees shade a lot of yards here too. AgriLife says grass in shade should be kept at the highest recommended height so it has more leaf to catch light. If your front yard sits under a big oak, that’s one more reason to stay tall.

What to do this week

1. Check your mower setting against the table above. If you’re below it, raise it.
2. If you’re still at your summer height, come down one notch at a time over the next few mows.
3. Keep mowing on your normal schedule while the grass is growing. Fall growth can be fast.
4. Sharpen the blade. AgriLife says a dull one crushes the grass instead of cutting it.
5. Leave the “last mow” for when the lawn actually stops growing.

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