Now is the time to consider frost seeding pastures—during February and early March. "If there is If there is no snow cover, this is the perfect time to frost seed existing pastures that are thin, or pastures where you would like to increase the percentage of legume in the stand," says Brian Lang, Iowa State University Extension agronomist in northeast Iowa.

Broadcasting seed in mid- to late winter gives time for freeze-thaw cycles to shallowly incorporate the seed. Some winter seasons have less freeze-thaw cycles than others, but fortunately, early spring rains also help with seed coverage on bare areas.

Red clover has been the most consistently successful forage species to establish with frost-seeding, he says. Other legumes can be frost seeded with slightly less success than clovers, and less success yet with ryegrass and timothy. Other grasses are difficult to establish with frost seeding because the seeds are larger or are less competitive in initial emergence.

Frost seeding is easiest, least expensive

"Iowa farmers have had the best experience when the legume seed is broadcast on the thinnest, least vigorous pasture areas," says Lang. "Success has also been improved where the previous grass stand has been heavily grazed, thus, exposing more areas of bare soil. Successful frost-seeding also requires average to better than average rainfall in spring."

While frost-seeding is the easiest and least expensive pasture seeding approach, using a drill for more precise seed placement and seeding when soil conditions are more supportive of quick germination, such as in April, usually provides better and more uniform stand densities, he notes.

Lang lists the following information available as fact sheets online:

1) Improving Pastures by Frost Seeding
http://www.extension.iastate.edu/Publications/PM856.pdf.
2) Interseeding and No-till Pasture Renovation
http://www.extension.iastate.edu/Publications/PM1097.pdf.
3) Interseeding Small Seeded Forages with Conventional Corn Planters
http://www.extension.iastate.edu/Publications/PM1097.pdf.
4) Selecting Forage Species
http://www.extension.iastate.edu/Publications/PM1792.pdf.
5) How Pasture Plants Grow
http://www.extension.iastate.edu/Publications/PM1791.pdf.
6) Soon to be available from the University of Wisconsin, Frost Seeding Red Clover into Winter Wheat
http://ipcm.wisc.edu/WCMNews/tabid/53/EntryId/667/Frost-seeding-red-clover-into-winter-wheat-publication.aspx.