Though warm season lawns don’t go dormant until late fall or early winter, getting them ready for dormancy begins in the late summer. Lawn care choices made in August, September, and October directly impact how well the grass will overwinter. The healthier a lawn is during the growing season, the stronger it will come back next spring.
Last Fertilizer Date
Warm-season grasses won’t need fertilizer while they’re dormant over the winter months. The last application of fertilizer for the year should be done during the first week in September. This will help keep the lawn green for as long as possible, often into November, and strengthen the grass for overwintering. Fertilizing later in the fall can stress the grass and promote top growth instead of deep roots that will keep the lawn healthy over winter.
A spreader is the easiest way to apply dry fertilizer across the lawn. Use fertilizers sold as all-purpose lawn food, or specifically formulated for Southern warm-season grass. Lawn fertilizers are generally high in nitrogen, and application rates are based on the amount of actual nitrogen in the fertilizer. Always read and follow label directions for application rates and spreader settings.
Overseeding?
If you really want a green lawn in the winter, you can sow annual ryegrass seed over the warm-season lawn in September. This cool-season grass will grow green while the permanent lawn is dormant. It will need regular mowing and watering over the winter, just like a regular lawn needs during the rest of the year.
To overseed a lawn, mow the grass as short as possible and then rake the lawn or use a vertical mower to remove thatch. Sow grass seed using a spreader set to apply 10 pounds per 1,000 square feet. Rake the ground again to make sure the seed moves close to the soil. Until seed begins to germinate, water the lawn lightly 2 or 3 times a day. Once the grass is growing, water only enough to keep the ryegrass from wilting, since too much water can damage the dormant warm-season grass. Fertilize the lawn after it has been mowed twice, using 1/2 pound of nitrogen per 1,000 square feet. For a complete fertilizer with a nitrogen-phosphorous-potassium ratio of 10-2-2, for example, this means applying 5 pounds of fertilizer per 1,000 square feet.
Mowing and Weeding
Continue mowing as long as the grass is actively growing, typically into November for a well-maintained lawn that is not overseeded. Lawns that are overseeded will require year-round mowing. Lawn mowers can be set to cut a little higher in the fall, since longer grass blades encourage deeper root growth.
Since dormant lawns are not actively growing, they cannot compete with weeds. Combat winter weeds by applying a pre-emergent herbicide in late August or early September before annual winter seeds begin growing. Do not apply a pre-emergent herbicide if overseeding with ryegrass, as that will prevent the grass seed from sprouting. Perennial weeds that show up can be spot-treated in a dormant lawn by spraying with a post-emergent herbicide like glyphosate.
