Fall and Winter Care for St. Augustine Grass

October: protect against weeds and fungus

Fall is when the two biggest cool-weather threats set up: winter weeds and large patch fungus.

• Apply pre-emergent early in the month. It stops cool-season weeds like annual bluegrass, henbit, and stickers before they sprout. Once you can see them, pre-emergent is too late. See safe weed control.
• Apply a preventative fungicide. Large patch becomes active as soil cools. Getting ahead of it is much easier than treating it. I use Scotts DiseaseEx for this October round. See large patch fungus.
• Keep mowing at 3½ to 4 inches as long as it's growing. Growth slows, so you'll mow less often.

November: feed the roots

Finish the year with a fall fertilizer that's lower in nitrogen and higher in phosphorus and potassium. The Turf Method program uses Nitro-Phos Fall Special 8-12-16 in early November. The goal is stronger roots and winter hardiness, not a flush of new leaves. Heavy nitrogen in fall feeds large patch and leaves soft growth exposed to cold.

Watering: taper off

As temperatures drop, the lawn uses far less water. Cut back to short, twice-weekly waterings in fall and skip them after a good rain. Water in the early morning only. Wet grass overnight in cool weather is exactly what large patch wants. By December, shut off and winterize the irrigation.

During dormancy, water only if you hit a long dry stretch. If a hard freeze is in the forecast and the soil is dry, a watering a day or two ahead helps. Moist soil holds heat better than dry soil.

Leaves

A light layer of leaves can be mulched right into the lawn with the mower. Thick layers need to be raked or bagged. I rake those into a Fiskars pop-up yard bag. It stands open on its own. Leaves that pile up and mat down block light and trap moisture against the grass, which smothers it and invites fungus.

Winter dormancy and freezes

St. Augustine goes dormant and turns tan or brown after the first frosts. That's normal. A few things to keep in mind over winter:

• Stay off frosted grass. Walking on frozen blades crushes them and leaves brown footprints.
• Don't fertilize a dormant lawn. Wait for spring green-up.
• Don't judge freeze damage in January. Wait until the lawn greens up in spring to see what actually needs repair. See dormant or dead?
• Use the downtime. Clean your equipment and sharpen your mower blade so it's ready. A blade removal tool and a cone balancer make this a quick job.

Late February: get ready for spring

The spring work starts before the lawn greens up: pre-emergent in early February, then a light dethatch, aeration, compost, and the first feeding late in the month. The lawn calendar has the full list.

Common questions

Does St. Augustine grass go dormant?

Yes. St. Augustine goes dormant and turns tan or brown after the first frosts, then greens up again in spring. It's normal and doesn't mean the grass is dead.

Should I water St. Augustine in winter?

Only during a long dry stretch. A watering a day or two before a hard freeze helps if the soil is dry, because moist soil holds heat better.

Should I fertilize St. Augustine in winter?

No. Feed with a low-nitrogen, high-potassium fall fertilizer in early November, then wait for spring green-up. A dormant lawn can't use fertilizer.