Hey, moccasin! I'll give you the short version of my take on the benefits of overseeding and go into it more later.

Overseeding your permanent warm season lawn with annual ryegrass (a cool season grass) has no benefits whatsoever and may, in fact, cause damage. Annual rye does not fix nitrogen nor improve the soil.

The only time I would recommend the use of ryegrass is for a winter cover over BARE soil to prevent wind and water erosion of the soil....or to provide a winter grazing crop for certain livestock.

Our warm season grasses (bermuda, centipede, St. Augustine, bahia, etc.) all require a cold weather dormancy. The best thing we can do for those grasses is to allow them that dormancy without the affront of more watering, fertilizing, and mowing all through the winter. Golf courses must over seed, but golf courses have the money to replace their declining greens and to cover them with layers of insecticide and fungicides all year long.

More later....but this should give you something to ponder. ;-)

Just wanted to stress that overseeding annual ryegrass is only a problem for our established LAWNS. (Was that clear?) It competes for space above and below ground, uses available water and nutrients, impedes air flow and gas exchange, and may even have allelopathic properties that could be harmful to the permanent grass. I see a great deal of SAD (St. Augustine Death) and Centipedegrass decline since overseeding has become so popular, along with all of the other fungal disorders that can be a problem on weakened turfgrass.

I like the fact that warm season grasses turn brown in the winter. The spring greenup is a lot more special. And the grass just plain needs a winter's rest.

All that said, it is a good option for a winter cover crop for bare fields and gardens. It certainly increases the organic matter content when tilled in after the winter, or even not tilled in. But it doesn't fix nitrogen like the clovers do.

Let me know if you have any questions!

Rhizo, you've given me enough information to allow me to lighten my burden this winter. No overseeding for me.

We have a mix of grasses in our lawn, with St.Augustine in the back and in some cool spots under the shade trees. I finally learned what SAD was, so thanks for that too. I love the St.A but must be content with it in the back yard only. Too sunny on the western exposure.

Well, I'll be letting my grass REST this winter. But we do have our newly cleared "back forty", where ancient azaleas were cut down and their locations had no grass, and I am wondering if this fall would be a good time to overseed with the crimson clover? Should I just let it grow and not cut it until spring? We will NOT be tilling the ground, just covering it up so it won't be a mud wallow over the winter. Or would that area, about 25x100, be fine for the annual rye grass? Actually, we bought that portion of our neighbor's lot inside the city here, and took out everything (the 50 yr old mostly dead azaleas, trash camphor trees) except we left three young pecans and 2 huge ancient sasanquas. I wanted to sod it with St.A, but DH said too much preparation required, so we'll just do the best we can.