WINTER SOWING
Winter Sowing (also called dormant sowing) is a propagation method used throughout the winter
where temperate climate seeds are sown on the ground or into protective vented containers
and placed outdoors to foster a naturally timed, high percentage
germination of seedlings.This is a great way to start milkweed plants for Monarch butterflies, as well as nectar source plants such as new england asters, purple coneflowers, etc. for planting next spring. It provides natural cold stratification of the seeds and they will begin growing when the conditions are right.
WINTER SOWING DIRECTLY IN SOIL
http://extension.agron.iastate.edu/NPKnowledge/soiltemphistory.html
Strip off any sod, weeds or grasses. Cultivate the soil to a fine tilth, firm the soil by treading on it, and rake lightly. Sow the seed (you can mix it with sand if you are broadcast-sowing). Some people just spread the seed on bare ground and walk on it to ensure seed/soil contact.
When conditions are right in the spring, your seeds will germinate!
WINTER SOWING IN CONTAINERS
MINIATURE GREENHOUSESTrudi Davidoff recommends sowing seed in miniature greenhouses (made from recycled water and milk jugs) and placing them outdoors. Please visit the below links to find out more.
http://www.wintersown.org/
and Step 2 http://monarchbutterflygarden.net/winter-sowing-milkweed-seeds-prepare-containers/
Here is a ,pdf brochure that explains Trudi's method
Other links:
Winter Sowing - A step by step guide from "Get Busy Gardening"
A Step to Step Guide to Winter Sowing from Bacman's - in the Minneapolis area
There are also a number of videos on YouTube about winter sowing from which to learn!