Seeds can also be sown directly into the soil but keep in mind that soil temperature should be below 50 degrees to avoid early germination, and before the soil freezes.
If you decide to winter sow, grow extra plants and SHARE with others!
Below is a copy of a post made last year about winter sowing, with some changes and additions.
WINTER SOWINGWinter Sowing (also dormant sowing) is a propagation method used throughout the winter where temperate climate seeds are sown into protective vented containers and placed outdoors to foster a naturally timed, high percentage germination of climate tolerant seedlings.
This is a great way to start milkweed plants for Monarch butterflies, as well as nectar sources 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.
Trudi 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.
and Step 2 http://monarchbutterflygarden.net/winter-sowing-milkweed-seeds-prepare-containers/
Here is a ,pdf brochure that explains Trudi's method
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!
SOWING DIRECTLY IN SOILNovember and December are good months sow seeds on bare ground. Just make sure the soil temperature below 50 degrees but before the soil is frozen. Here is a map from the Iowa State Extension that shows current soil temperatures. http://mesonet.agron.iastate.edu/agclimate/display.php?src=/agclimate/daily_pics/4in-temp-out.png
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 mixture (with fine sand for even distribution) at a rate of 1/8 oz per sq. 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!