Most gardeners look forward to winter as a time to rest, plan, and daydream about next year’s garden using the tempting seed catalogs that begin to fill our mailboxes in the holiday season. We don’t typically think of winter as a time to get our gardens started. But if your daydreams involve filling those annoying holes in the border where plants haven’t filled out as expected, or perhaps extend to creating that cutting garden you’ve always wanted, winter is the time to get started. If you have a seed packet, some seed-starting mix, and a place outside where you can store a container, you can use winter sowing to get a jump on next year’s growing season.
Winter sowing is a technique that uses the plants’ own evolved mechanisms for reproduction. In the wild, plants reproduce by dropping seed onto bare ground, where it experiences the rain, ice, snow and temperature fluctuations of the dormant season. When spring arrives and temperatures begin to regulate, the seeds break dormancy and send out a radicle, or root hair, followed by seed leaves, called cotyledons. The plants carry on their life cycles without the intervention of a gardener.
Many plants, both annual and perennial, vegetable and ornamental, can be propagated using this technique. It can be done gradually, as the gardener has time. The best time to start is anytime after the winter solstice.
How to Winter Sow:
1. Repurpose containers found around your house. Plastic gallon or half-gallon milk jugs cut in half horizontally, takeout containers (clamshell or two-part containers with clear lids), and plastic tubs from prewashed salad greens make excellent winter sowing containers. Using a knife or pair of scissors, make several slits or holes in both the bottom and the lid of the container. The bottom holes provide drainage; the top holes allow water to penetrate while protecting your seeds from hungry foragers.
2. Using duct tape and a waterproof, permanent marker, label the contents of your container and apply the duct tape to the underside of the container. Doing so helps prevent sunlight from fading the label. Alternatively, use pencil and a store-bought seed flat label and stick the label in the soil mix.
3. Fill the container with soilless seed starting mix, available at garden centers and home improvement stores. Do not use potting mixes with weed control additives; those chemicals will prevent your seeds from sprouting.
4. Water the container until it drains freely from the bottom.
5. Sprinkle the seeds onto the soil surface. Very fine seed, such as that of foxgloves, perennial poppies, or lettuce, does not need to be covered. Otherwise, cover with a layer of soilless mix, sand, or vermiculite to the depth indicated by the seed packet. If you can’t find instructions, plant the seeds twice as deep as they are thick. Tamp them gently into the soil surface with your hand or the base of a pot.
6. Water gently again. The spray attachment to your kitchen sink works perfectly. Take care not to flood the seed. Cover the container with its lid.
7. Set the container outside in a spot where it will be exposed to the weather, but out of the way of most animals. The top of a picnic table makes a great spot, but the ground is just fine. Make sure the container is not protected by the eaves of your house, or it will dry out.
8. Leave them alone until about five weeks before the average last frost date in your area, when the lids may be removed to allow seedlings to harden off completely.
If you fiddle with the containers in the meanwhile, you’re missing the point. The beauty of the winter-sowing technique is that it requires no further intervention by the gardener until spring, when it’s time to transplant. The seedlings will be naturally hardened off by their exposure to the elements. They’ll survive just fine without additional nutrients; the seed has all the nutrients the plant needs until it can photosynthesize on its own. Just settle down by the fire and get back to those catalogs.
Here are lists of just a few plants that perform well using winter sowing:
- Ageratum (floss flower)
- Alyssum (sweet alyssum)
- Antirrhinum (snapdragons)
- Calendula (pot marigold)
- Celosia (cockscomb)
- Centaurea (cornflower)
- Dianthus chinensis (China pinks)
- Gypsophila (baby's breath)
- Helianthus (sunflowers)
- Malva (mallow)
- Nicotiana (flowering tobacco)
- Sweet peas
- Tithonia (Mexican sunflower)
- Torenia (wishbone flower)
- Blanket Flower
- Blazing Star
- Butterfly Weed
- Coral Bells
- Hardy hibiscus
- Lily (Oriental varieties)
- Pincushion Flower
- Red Hot Poker (Kniphofia)
- Rose Campion
- Russian Sage
- Salvia (varies by species)
- Sedum (varies by species)
- Shasta Daisy
- Alliums (onions, shallots, garlic, chives)
- Asian vegetables
- Brassicas (cabbage, broccoli, kale, collards, etc.)
- Corn (early types)
- Cucurbit family (cukes, squash, pumpkins, melons, gourds)
- Herbs (edible and ornamental)
- Nightshade family (eggplant, tomatoes, peppers)