What is the Winter Sowing method of seed starting?
An effective, simple, and low-cost seed starting method, Winter Sowing is the process of starting seeds in containers outside during the winter months. Planting seeds in clear or translucent containers, such as milk jugs, creates a greenhouse effect, trapping heat and moisture, thus allowing the seeds to naturally stratify in the winter environment. As temperatures fluctuate, seeds are protected from the harsh winter elements and are exposed to natural freeze-thaw cycles. This exposure hardens the seeds and results in sturdy seedlings that are already acclimated to outdoor conditions.
What equipment is needed to start seeds when Winter Sowing?
- Recycled, clean and well-rinsed milk jugs (Using jugs and bottles, salad containers, or storage totes have also been used with success)
- Sharp scissors
- Exacto knife
- Plant labels
- Weather resistant marker
- Duct tape
- Seeds suited to winter sowing
Step One: Prepare the jugs for seed starting
Cut the container horizontally in half about four inches up from the bottom leaving a small hinge to allow for easy opening and closing. The small area of plastic directly below the handle is a great location for the hinge.
Make four to six holes in the bottom of the jug with a sharp knife or screwdriver to allow for drainage. This is essential as the jugs are open to the elements and this allows moisture to freely drain out of the bottom.
Fill the bottom four inches of the jug with a quality potting mix that has been moistened. The soil should hold its shape when squeezed.
Step Two: Choose suitable seeds for Winter Sowing
Not all seeds are suitable for this seed starting method. Choose cold hardy seeds that will tolerate winter sowing and follow the instructions on the seed packet as directed for spacing and depth of planting. Some good choices include:
Amaranth, Aster, Bachelor Button, Bells of Ireland, Broccoli, Calendula, Cauliflower, Coneflower, Cosmos, Foxglove, Hollyhock, Lupine, Milkweed, Oregano, Radish, Rudbeckia, Salad Greens, Thyme, and Yarrow.
Step Three: Label and seal the jug
It’s helpful to label both the outside of the jug and include a plant label inside. Seal the jug closed. Use duct tape to connect the cut edges back together all the way around. Leave the top open. Keeping the cap off provides ventilation.
Step Four: Set the jugs in a sunny spot outside
The jugs generally stay moist throughout the winter enduring rain, snow, and fluctuating temperatures. Water if needed. Open jugs in spring after seeds sprout and danger of frost has passed. When seedlings are at least two inches tall with two sets of true leaves, begin transplanting the seedlings into your garden beds or containers.
Starting seeds in containers outside during the winter months is a good way to grow sturdy seedlings that are already acclimated to outdoor conditions when it's time to plant in the spring. By trapping heat and moisture, the container creates a greenhouse effect, and the seeds are able to experience the required weathering process naturally at the same time that seeds are protected from the harsh winter elements.
This article by Sara Elledge, UC Master Gardener of El Dorado County, originally appeared in the Mountain Democrat in December 2025.
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