The winter sowing method is a technique for starting seeds outdoors during the colder months by using containers such as milk jugs to create a greenhouse effect. According to Sara Elledge, UC Master Gardener of El Dorado County, this approach involves planting seeds in clear or translucent containers that trap heat and moisture. This setup allows seeds to naturally stratify while being protected from harsh winter conditions.
To begin, gardeners need recycled and cleaned containers like milk jugs, sharp scissors or an Exacto knife, plant labels, a weather-resistant marker, duct tape, and seeds suitable for cold weather. The process starts by cutting the container horizontally about four inches from the bottom while leaving a hinge near the handle for easy access. Holes are made in the bottom for drainage before filling it with moistened potting mix.
Elledge advises choosing cold-hardy seeds that can withstand winter sowing and following packet instructions for spacing and depth. Some recommended varieties include amaranth, aster, broccoli, calendula, coneflower, foxglove, milkweed, oregano, radish, salad greens, thyme, and yarrow.
After planting the seeds and labeling both inside and outside of the jug for identification purposes, gardeners should seal the container with duct tape but leave the cap off to provide ventilation. The sealed jugs are then placed outside in a sunny location where they will be exposed to rain and fluctuating temperatures throughout winter.
“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,” said Elledge.
Once spring arrives and after any risk of frost has passed, gardeners can open their jugs once seedlings have sprouted. When seedlings reach at least two inches tall with two sets of true leaves, they can be transplanted into garden beds or other containers.
This information was originally published by Sara Elledge in December 2025 in Mountain Democrat. For those seeking further guidance on winter gardening techniques or advice specific to their region’s climate challenges related to seed starting methods like winter sowing—UC Master Gardeners of El Dorado County offer support through an online survey tool where questions can be submitted directly for expert feedback.
