| I hope this isn't too late, but do NOT NOT NOT NOT Do NOT use the cheap 40-pound bag of topsoil for winter sowing. This is topsoil (not potting soil, and even potting soil should not be used on its own in WS) and great for outdoor use but, WS needs a combination of organic and inorganic soil. The big $1 bags of topsoil or not only weedy, but they also settle and turn to something similar to a brick over the winter in your WS container. It does not have enough air pockets for WS. Also, do NOT use soil starting mix for WS--it's ONLY inorganic materials and too light and fluffy for outdoors. It does not have the moisture retention needed in WS. Just right is a soil MIX. As cheap as I am, I do pay for these as it more than pays off in sprouting success rate. I like: - Miracle-Gro Potting Mix (NOT Moisture Control) (settle with LUKEWARM water)
- Premier Pro-Mix for Potting-Seeding (settle with WARM water)
- Premier Pro-Mix Ultimate Potting Mix (settle with WARM water) Do NOT buy soil mixes with weed suppressants as they suppress ANY germination, including that of your seeds. You also do NOT need to pay for moisture crystals; they may retain too much moisture in the WS containers. As suggested, you can mix your own. Any combo of organic and inorganic ingredients is OK (sort of like how everyone has their own chili recipe!). I use:
8 parts potting soil
1 part perlite
1 part vermiculite
4 parts sphagnum peat moss
4 parts compost Because it's hard to find all these things, and not inexpensive, I do prefer the pre-mixed mixes. Hope this helps,
Monica | 
