I overseeded our winter-dormant centipede lawn last fall with annual ryegrass. It made a beautiful green lawn in the front yard and a small oval in the Upper Garden. No watering, no fertilizer. Today He-who-mows, who had not been enthusiastic about the overseeding when I did it, said he thought we should have planted a broader area, taking in the backyard and the pecan patch.
You can read about the benefits of planting a cover crop here. University Agriculture sites such as Purdue and Cornell Universities have similar documentation.
The Pecan Patch in the background could have been green now, too.
The Oval Lawn in the Upper Garden
Loropetalum trees on the north side of the Oval Lawn
Annual rye will die when the weather gets hot and regular perennial grasses overtake it. Nitrogen fixing and extraction of potassium and phosphorus from the subsoil will benefit the lawn. Any stray grass clumps in flower beds are easily pulled.
Maybe next year, all will be green. A 50 pound bag of annual ryegrass seed costs less than $15.00. The return is priceless.