Although many gardeners think seeds need lots of light and warmth to grow, winter sowing proves that many seeds actually thrive without either of these things. Essentially, winter sowing mimics nature by exposing seeds to lots of cold and rain. The seeds crack open during snows or frosts (so you don't have to nick seeds open by hand, as many gardeners do), and begin sprouting when it is safe for them to do so. For this reason, winter sowing may only be done in winter. The earliest time to begin winter sowing is after the winter Solstice (at the end of December); you may continue winter sowing as long as it's cold enough during the late afternoons that you need a jacket to feel comfortable.
What Can be Winter Sown?Not all seeds are suitable for winter sowing. Most tropical plants are out, but almost all wildflowers and herbs are good choices. Seed packets that indicate the seeds easily self-sow or should be planted in the fall for spring growth, colonize easily, are "hardy," may be direct sown in the garden, or needs pre-chilling, stratification, refrigeration, are also good choices, as are seeds from cold regions (for example, plants with cold-place names in their titles, like "Alaskan Peas").
Some edibles that can be winter sown include artichokes, beans, beets, Bok Choy, broccoli, cabbage, carrots, celery, chard, chives, collards, early types of corn, eggplant, garlic, kale, lettuces, okra, onions, parsnips, peas, peppers, potatoes, pumpkins, radishes, shallots, spinach, squash, and tomatoes.
Potting soil (fresh, but not the moisture control type)
Duct tape and Sharpie pen or metal plant markers and a pencil
Almost any type of plastic container with a well-fitting clear or nearly clear lid works fine. I prefer the clear, lidded boxes bakeries use for selling cookies and donuts, but many gardeners use plastic milk jugs and soda bottles (with the lids cut off, then taped back on), Cool Whip tubs, or whatever else they have laying around. Ask your friends to help you save containers, or visit your local grocery store and ask for the bakery containers, like I use. I purchase mine from the store for a few dollars and they last me several years.
How to Winter Sow
1. Using a pair of scissors, carefully poke about five slits in the bottom of each container. These are water drainage slits to prevent your containers from becoming too wet. If your containers are made of thick plastic, drill a few holes in their bottom, instead.
2. Cut two or three slashes on the lid of the container, too.
3. Fill each container with new potting soil. The soil only needs to be an inch or two thick, but some gardeners prefer to use about five inches of soil, so the roots grow fuller and deeper.
4. Water the soil well with a watering can and allow it to drain for a few minutes.
5. Plant seeds in the soil. Plant only one type of seed per container, because it’s sometimes difficult to tell seedlings apart.
6. Label each container; if you use duct tape, make sure the container is dry before applying the tape. It’s best to place labels on the sides of the containers — not on the bottom (where they interfere with drainage) or on the lid (because they’re apt to fade in the sun — and you’ll eventually cut away most of the lid, anyway). If you’re using metal plant markers, just lay them inside the containers.
7. Close the containers and place them somewhere out of the way. They should not be sheltered; you want the containers exposed to the weather. For example, you could place the containers along your fence line, but not beneath your carport. Don’t worry about giving the seeds “enough light.” In nature, seeds can germinate without any light at all. After closing the lids, you’ll notice that within a few minutes, the containers appear foggy. They are now acting as a mini greenhouses for the seeds, keeping them relatively warm and moist. This mimics the best conditions of nature.
8. Check on the seeds every few days. The contents of the container will freeze and thaw repeatedly. That’s okay! In fact, it’s good. Because of this freezing and thawing, you don’t need to nick or cut into seeds before planting them.
9. When green shoots begin to appear (often toward the end of winter, but sometimes a bit later), check the containers for moisture content. It’s just fine to do this when it’s cold, but don’t open container lids if it’s freezing. If the soil seems less than moist, give the seedlings a little water, then put the lids back on the containers.
10. As the seedlings grow, check them at least every other day. To help them acclimate to the outdoors, begin adding an extra slash or two to the container lids every week or so.
11. When there is more open space on the lids than there are actual lids, you may transplant your seedlings. They may be teeny-tiny, but that’s okay. These baby plants are hardened and acclimated to outside conditions; there’s no need to follow traditional “hardening off” procedures.
12. Once you plant your seedlings, give them a gentle drink and keep them moist but not wet.
13. If your containers are drying out too much, it’s probably because there are too many drainage slits. To remedy this problem, dry off the bottom of the container with a rag and use duct tape to cover one or more drainage slits. If your containers look too wet, simply use a knife to make additional slits in the bottom-sides of the containers.
For more information about winter sowing - and other seed sowing methods, including indoor sowing and direct sowing - check out my FREE ebook, "The Proverbs 31 Woman Guide to Starting Seeds."