I copied this from someone who knows more than I do. I have done both and wont waste my time seeding switchgrass late in the year again.

"have seeded both fall and winter and like others who have tried both it seems that late Janurary thru mid March seems to get a better germination rate then fall seedings. So IMO I would seed mid winter during a thaw on bare ground or at least no more then a few inches of snow.

One pound of seed sown at the proper time on properly prepared ground (sod killed previous to planting) and weeds controlled with herbicide is worth more then 100#'s planted the wrong time under the wrong conditions."