Overseeding your lawn for the winter

Is your lawn composed of one of the warm-season grasses, such as Bermuda grass, buffalo grass, zoysia or St. Augustine grass? Since such grasses go dormant in cool weather, Southern homeowners are faced with the prospect of enduring unappealing brown lawns during the winter. Fortunately, an alternative exists. It is known as "overseeding lawns."

"Overseeding lawns" is just what it sounds like: namely, you're sowing seed over existing grass. But the seed you'll use in the current project is not seed for one of the warm-season grasses, but rather annual ryegrass (Lolium multiflorum) -- a cool-season grass. Once it sprouts, annual ryegrass will provide you with a green carpet during the Southern winter, thriving in the cool temperatures. Just as importantly, annual ryegrass will die back when summer's heat returns, exiting in time for warm-season grasses to take center-stage again (otherwise, it would compete with the warm-season grasses, depriving them of sunlight, water and nutrients).
The work entailed in overseeding lawns that are composed of warm-season grasses is similar to that for overseeding lawns that are composed of cool-season grasses. Note, however, that the latter is based on thinking that is fundamentally different from the former:

• Seeds for the same type of grass are used (i.e., cool-season grass over cool-season grass).
• And overseeding is not used as a temporary measure to get through the dormant season. Rather, when overseeding lawns composed of cool-season grasses, the object is to fill in bare patches (permanently, one hopes).

Preparations for Overseeding Lawns

Mow the dormant lawn as low as you can. This will promote contact between seeds and soil (there will be less grass to get in the way of the seed) .

Another step you can take to promote contact between seeds and soil is core aeration, or "lawn aeration." This step will help reduce lawn thatch, which stands in the way between grass seeds and the soil they'd like to call home. Core aerators (or "lawn aerators") can be rented from local rental centers.
In severe cases, you may need to add a layer of topsoil before overseeding lawns. For instance, due to shallow tree roots popping up on the lawn, your topsoil layer may be too thin. Spread 1/4" of screened topsoil over such an area, and rake it in.

Overseeding Lawns

You'll need a spreader for this project. The bag of grass seed that you buy for overseeding lawns should have information on the back concerning recommended overseeding rates. Set the spreader to the recommended overseeding rate.

The grass seeds must be watered properly, in order to germinate. Use just a fine spray, as you don't want to create a flood! The soil should be kept evenly moist, which may mean several waterings per day (depending on the weather), for several weeks.

After the grass blades sprout, you'll still need to water a couple of times per day. If you know your schedule won't permit this, then it may be time to start looking into automatic irrigation systems. Although annual ryegrass will die in the summer, conveniently making way for warm-season grasses to take over, the annual ryegrass will still, nonetheless, be around in spring, offering unwanted competition with warm-season grasses. One way to minimize this competition is to mow the annual ryegrass as low as possible in spring. By keeping it short, you'll at least minimize the amount of sunlight that the annual ryegrass robs from your main lawn, which is now emerging out of dormancy.

The best time for overseeding lawns composed of warm-season grasses is fall roughly in October or November

(the left lawn was overseeded with winter grass, the right side was not)