Winter is the time when warm-season lawns across Louisiana take a much-deserved rest until spring. While lawns are not actively growing during much of the winter, the actions you take — and don’t take — between November and February set the stage for how your grass performs next spring. Here are some tips to keep your lawn healthy throughout the winter and ready to shine next spring.

Don’t Fertilize During Winter

Warm-season grasses such as St. Augustinegrass, centipedegrass, bermudagrass and zoysia are dormant or semidormant in winter. Fertilizer should only be applied to actively growing lawns. Fertilizer applied in winter won’t be used efficiently and may leach into groundwater. Additionally, that fertilizer could feed any freshly germinated winter weeds that have popped up in your lawn. Save fertilizer applications until the lawn greens up in April and we’re well past the threat of frost.

Weed Control

Winter weeds such as annual bluegrass (Poa annua), lawn burweed (sticker weed), chickweed and henbit can take over thin or stressed turf. Spring is not the time to treat lawn burweed; remove it before spring arrives.

• Preemergence herbicides (such as prodiamine, dithiopyr or isoxaben) applied in late fall or early winter can greatly reduce weed problems. Isoxaben is best for broadleaf weeds and is safe for our four major warm-season lawn grasses.
• Postemergence herbicides may be used during mild winter days (above 50 F) if weeds are already visible. Spray twice, once in late fall and again in winter. On St. Augustinegrass and centipedegrass, atrazine is the go-to for small winter broadleaves and some annual bluegrass suppression, with metsulfuron (MSM) excellent on lawn burweed, clover, henbit and chickweed (use light label rates). On bermudagrass and zoysia, skip atrazine if they’re still green; instead, use a three-way mix (2,4-D + MCPP/MCPA + dicamba) or MSM for broadleaf weeds. Avoid spraying near hard freezes, follow the label for your grass and spot-spray when possible.

Spring weeds like henbit can be controlled during the fall and winter using pre- and postemergence herbicides. Photo by Eric DeBoer.

Manage Leaves and Debris

A blanket of leaves blocks light, traps moisture and can incubate disease. You don’t have to bag every single leaf. Regular mulching with a sharp mulching blade on your lawn mower is fine and returns organic matter to the system. What is best to avoid is letting mats of oak or magnolia leaves sit for weeks. Those mats can smother the turf, keep the surface too wet, and create thin, bare patches that winter weeds love. Now is also a good time to blow any debris that may have accumulated in any shady corners to improve airflow.

Water Only if Needed

Winter evapotranspiration is much lower than in summertime. Dormant lawns aren’t using much water, and evaporative demand is low. In a typical Louisiana winter, rain more than covers turf needs. Irrigate only during extended warm, dry spells when the soil has actually dried out. Watering a dormant lawn without reason leads to soggy, cold soil and more weeds, moss and algae. Monitor soil moisture throughout the winter. If you’re on sandy soil or a raised profile that sheds water fast, check more often.

Mow Sparingly

Your grass is likely not growing during the winter, but cool-season weeds will. An occasional winter mow helps keep the canopy tidy and can prevent some weeds from flowering. Mow at your normal in-season height. Do not scalp. Scalping will expose stolons and crowns (meristems) to cold injury and encourages more winter weed germination in the opened canopy.

Winter Lawn Pests

Large patch (Rhizoctonia) is a fall-to-spring disease that flares with cool, wet weather, especially in zoysia and St. Augustinegrass. You’ll see orange-to-brown rings or arcs. Adjusting your cultural practices can be a major help: avoid excess moisture, skip fall nitrogen and improve airflow. If you have a yearly history, a preventive fungicide program in fall (and sometimes a late-winter touch-up) can be used; azoxystrobin, myclobutanil, propiconazole, pyraclostrobin and triticonazole will reduce the spread of large patch.

Diseases like large patch are the worst on overwatered turf. Photo by Eric DeBoer.

Plan Ahead for Spring

This is the time of the year to get the highest return on your investment.

• Soil test now if it’s been two to three years. A soil test will tell you whether you truly need phosphorous or potassium and whether your pH is drifting. If pH correction is needed, winter is a great time to apply lime (for low pH) or elemental sulfur (for high pH on appropriate soils).
• Service your equipment by changing oil and plugs, replacing air filters, and sharpening or replacing mower blades. If storing electric mower batteries, power them down to about 70% to 80% capacity for storage. Calibrate your spreader and sprayer. If you don’t calibrate, you’re guessing, and guessing is why lawns get striped or burned.

Eric DeBoer, Ph.D.
Assistant Professor