Winter Sowing

Now is the time to get your supplies ready for winter sowing of seeds that need stratification or cold, moist conditions in order to germinate.  The sowing time in our zone 5 area for these seeds begins with the Winter Solstice, December 21^st. 

Look for seeds that are described with the following terms: reseeds; colonizes; self-sows; hardy seeds; seedlings can withstand frost; sow outdoors in late autumn or early winter; sow outdoors in early spring while frosts may still occur; needs pre-chilling; requires stratification.  This group includes native plant seeds such as milkweed, black-eyed Susan, purple cone flower, liatris, lobelia, penstemon, and cool season annuals such as snapdragon, pansy, and nasturtium.

Start with a clean milk jug in which you have drilled holes in the bottom of the container for drainage and also along the top for ventilation. Discard the milk jug cap.  Mark a circular line 4″ above the bottom of the jug  and cut along your line leaving the handle area intact creating a hinge.  Place a coffee filter in the inside bottom of your jug and then fill the bottom half of your jug with potting mix.  Moisten the soil.  Plant your seeds according to package directions and pat them down so they make contact with the soil.  It is a good idea to plant only 1 variety of seed per jug.  Label the inside with a marker identifying the seed variety and date of sowing.  I found that cut up yogurt containers or blind slats make good markers. Seal your jug with duct tape and you now have a mini-greenhouse.

Put your containers outside in the winter sun, periodically checking to make sure that you see condensation droplets on the inside of the milk jug.  If you don’t see condensation, mist the soil.  It’s also a good idea to corral your jugs in a crate so that the wind doesn’t carry them off.

Allow Mother Nature to go through its freeze, thaw, snow and rain cycles and in the early spring check for germination. Once the seeds have germinated, start opening the jug for more ventilation to avoid overheating.  When the air temperatures reach 60^oF, discard the top of the milk jug.  These plants won’t need to go through the hardening process since they grew under natural conditions.

Barbara Burkhardt

Boone County Master Gardener

Resources:

“Starting Seeds in Winter”   Penn State Extension  https://extension.psu.edu/starting-seeds-in-winter

“What plants can I winter sow?”  University of Missouri Extension https://extension.missouri.edu/publications/ym105