How To Winter Sow Vegetables in 7 Easy Steps

Ready to start growing? Winter sowing is an easy and resourceful way to start spring vegetables early. It gives seedlings a headstart while working with natural conditions for germination. Gardening expert Katherine Rowe breaks down the steps to get winter sowing this month.

Two hands transplanting a seedlings, placing it inside the moist soil.

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As we hone in on our spring seed selections, it may be just the right time to get sowing. Winter sowing lets us start ahead of spring, giving us our garden fix while providing a foundation for sturdy seedlings.

In mild climates, you may be able to directly sow cool-season vegetables now, with the anticipated final frost four to six weeks away (and in frost-free climates, lucky you!). Meanwhile, in extra cold growing areas, look to the winter sowing method to insulate seeds until conditions are right for germination.

In winter sowing, seeds hold over the winter in homemade mini-greenhouses with exposure to natural elements. As seedlings sprout, they develop sturdy roots poised for vigorous growth and early flowering and fruiting, with no hardening-off period at transplanting. The method uses repurposed plastic containers and minimal supplies, making it easy to accomplish and with minimal oversight.

January and February are prime to winter sow vegetables, especially those that are cold-hardy and thrive in spring. Flowering ornamentals and edibles get a jumpstart with this fun seed-starting method.

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What is Winter Sowing?

Close-up of multiple white reusable plastic jugs used for cold stratification, each containing sown seeds, partially covered with a fresh layer of white snow.
When placed outdoors, the seeds receive all they need to germinate.

Direct sowing is the most streamlined way to winter sow. Direct sow cold-hardy selections that can go right in the ground in late winter. Depending on your climate, this may be a workable option for root vegetables susceptible to taproot disturbance at planting. The taproot is the part we want to foster and protect, and seeding in their bed or container avoids damage while transplanting.

Carrots, beets, parsnips, kohlrabi, and turnips are best direct sown before the final frost. Direct sow spinach, swiss chard, and other greens when soil temperatures are above 40°F or 4°C (about four to six weeks before the last frost).

The other winter sowing method exposes seeds to natural conditions while warming the ambient air with an insulative container. Placed outdoors, the seeds receive all they need to germinate (light, water, oxygen, and temperature variation). 

The Method

Transparent containers like milk jugs become growing vessels.

A mini-greenhouse situation promotes germination with exposure to cold temperatures and garden conditions, with protection. Seedlings emerge when temperatures warm and meet their germination requirements. With exposure, they develop strong roots for easy transplanting.

The streamlined seed-starting technique uses basic household supplies, making it resourceful, budget-friendly, and accessible to get growing early. It saves indoor growing space and time spent managing seedlings in a controlled environment. Mid to late winter is the time to winter sow, ideal for cold climates.

To winter sow, the “greenhouses” are repurposed plastic containers. Transparent containers like milk jugs, plastic bottles, salad packages, bins, or baggies become growing vessels with a few easy modifications.

The little greenhouses sit outside in a sunny spot, exposed to the elements, including snow and rain. The seeds benefit, and seedlings toughen up in the natural conditions as they sprout later in the season.

Advantages

Winter sowing supplies are budget-friendly, easy to make, and use basic household items.

The resourceful way of promoting germination works with natural conditions. Seed starting is accessible without a lot of supplies or intensive management.

Advantages of winter sowing:

  • Budget-friendly and easy
  • Space-saving, freeing up indoor growing space demands
  • Allows for early seed-starting
  • Works with nature
  • Provides cold stratification
  • Good germination rates and works for most seeds
  • No hardening off period
  • Low maintenance
  • Yields hardy seedlings for easy transplanting

Select Vegetables to Winter Sow

The plant features broad, smooth, light green leaves that form a rosette, with a crisp texture and a central stalk that is succulent and tender.
Leafy greens get sweeter with exposure to cold temperatures.

Winter sowing is versatile for most home garden seeding, including vegetables, herbs, flowering annuals, and perennials. Hardy perennials are reliable, as are frost-tolerant annuals and vegetables that thrive in cool weather.

Brassicas are perfect for winter sowing as they flourish in spring and tolerate light frost. The genus includes broccoli, kale, cabbage, cauliflower, and bok choy, among others. The leafy greens get sweeter with exposure to cold temperatures. Onions and peas, too, get a headstart when winter sown.

Heat-loving and frost-sensitive selections like tomatoes, peppers, and eggplants germinate when air and soil temperatures warm later in the season. Experiment with starting these when you winter sow your early veggies or wait until February or March in cold climates to stage them closer to consistently warm temperatures. They may germinate later than the cool-season growers; just give them a little longer in their containers.

Time the Winter Sow

Seedlings planted in a small container with wooden stakes.
Even seeds that don’t require cold stratifying benefit from exposure in “cold storage” until sprouting.

As early as December and January, you can winter sow. Climate and temperature affect germination, and starting in freezing conditions ensures seedlings won’t sprout too early and risk freezing again later. Cold weather ensures the stratification period for those that need it while staving off germination until conditions are consistently temperate. Even seeds that don’t require cold stratifying benefit from exposure in “cold storage” until sprouting.

Aim to sow seeds about six to eight weeks before you would typically transplant them to the garden bed or outdoor container. January is the time to winter sow seeds that benefit from cold stratification (and into February and March in cold climates). In warm zones, the seeds germinate faster.

Prep Your Containers

young plants growing inside a plastic bottle placed on top of the soil.
Stored outside, the vessels collect seasonal moisture from snow and rainfall.

There’s room to get creative when it comes to ”greenhouse” choices. Start with clear or very transparent containers like milk jugs, two-liter bottles, bins, or freezer bags. It needs to let light penetrate and have the capacity for drainage, ventilation, several inches of soil, and room for seedling growth. Clean the containers in warm, soapy water to sanitize them.

The containers need simple modifications to account for temperature variation and sprouting. We’ll cover a few basic containers (milk jugs, bottles, and freezer bags) that allow for opening and closing for airflow and temperature regulation.

Stored outside, the vessels collect seasonal moisture from snow and rainfall. Drainage holes are essential in preventing rot and other fungal problems. Make four to six holes in the base of the container. Label and date and the variety on each with a permanent marker.

Additional translucent containers for winter sowing:

  • Salad greens packaging
  • Deli veggie tray/cake/cookie container or clamshell
  • Large takeout containers

Milk Jugs

Several white translucent milk jugs cut in half and filled with soil and seeds.
The cut makes a hinge at the handle to open it on warm days.

To adapt a milk jug for winter sowing vegetables, remove the cap and poke the drainage holes in the bottom. Cut the jug nearly in half just below the handle, almost all the way around (about three-quarters). Leave the handle portion attached as a means to lift the lid during the season. The open cap allows airflow and moisture in the container, while the cut makes a hinge at the handle to open it on warm days.

Add three to four inches of potting mix to the base. Sow seeds according to the depth and spacing of the packet guidelines, covering them lightly or gently pressing them for soil contact as the seed requires. Water them in, and tape the jug’s cut seam.

Plastic Bottles

Close-up of little snapdragon seedlings with tiny cotyledons in a plastic bottle filled with soil.
Soda bottles make protective little greenhouses.

Two-liter water or soda bottles make protective little greenhouses. Prep them as you would a milk jug by removing the caps and making a cut three-quarters of the way around. Leave four inches of space at the bottom of the bottle for soil and seedling growth. 

With drainage holes in place, add three to four inches of soil. Sow the seeds according to packet directions and moisten the media. Tape the cut seam and place the bottle outside, cap off.

Freezer Bags

Blue cardboard packaging filled with transparent zip-lock freezer bags.
Resealable freezer bags are great for winter sowing.

Gallon-sized resealable freezer bags become seedling pouches by clipping the bottom corners and cutting slits or holes for drainage. Add several inches of soil and sow accordingly. Water the seeds for even moisture.

Leave an inch or so of the seal open at the top of the bag for ventilation. To adjust airflow and regulate temperature on warm days, open the seam more. In spring, roll the seal down like a cuff for full exposure, closing it if necessary on chilly nights.

To stabilize the bags, string them along a skewer by piercing the tops. The bottom should rest on a tray, crate, or bin.

Seeding

The mix should be light and fluffy with good aeration, drainage, and moisture retention.

Winter sow vegetable seeds in the containers according to their recommended spacing. A high-quality potting mix is best. No special seed mixes are necessary.

Avoid regular garden soil or straight compost, both of which are too dense for seeding. The mix should be light and fluffy with good aeration, drainage, and moisture retention. Don’t use any with moisture control or added fertilizers – a regular potting mix works well. 

Situate Outdoors

Several rows of white reusable plastic milk jugs covered with a layer of snow in a winter garden near the wooden wall of a barn.
Expose them to the elements, even snow.

Place the containers in a sunny location with access to natural moisture. Expose them to the elements, even snow. The seeds benefit, and seedlings harden off as they sprout later in the season. A southeast location is ideal for sunlight and warmth. If this becomes too sunny and warm toward spring or in warmer climates, move them to an east-facing spot with good morning sun exposure.

In windy areas, secure the vessels to keep them from blowing over. Nestle them against a foundation or wall, or place them in a milk crate, tray, or tub. Breezes help develop strong stems, but toppling over can disrupt the situation. Make sure the area is well-draining, too, so that the containers aren’t sitting in pooling water or puddles.

Maintain

Large plastic bottles with plants inside, lined up in a garden bed.
Condensation is a sign that moisture is available.

Winter sowing is hands-off until closer to spring. Often, and especially to start, precipitation from snow, rain, and condensation is enough to maintain soil moisture. Check containers once a week or so, especially as conditions become drier or warmer as the season progresses. With regular rain or snow, the vessels need only supplemental water or misting every few weeks. Watering needs may increase as temperatures warm and seedlings sprout. If the soil surface shows signs of drying, mist or sprinkle with water to prevent seeds or shallow roots from drying out.

Condensation is a sign that moisture is available. If it lessens, make sure soil moisture is adequate and that rain can enter the top. If not, add more openings. Keep tape in place at cut seams to prevent evaporation early in the process.

Vent the lid on warm days to allow transpiration and airflow to stave off diseases and to keep seedlings from getting too warm. Close the lid again before temperatures drop late in the day. As seedlings develop, this allows natural hardening-off that makes for easy transplanting without shock.

Transplant

Gloved hands carefully planting small green seedlings into dark ground.
Follow regular transplant guidelines for the best air and soil temperatures.

Not only is winter sowing vegetables resourceful and low maintenance, but it’s also highly productive, with good germination rates. Seedlings are ready to transplant after exposure to warm days in their open containers. Look for true leaves (fully developed leaves after the cotyledons) and a few inches of height as indicators of readiness.

Follow regular transplant guidelines for the best air and soil temperatures. To transplant, gently divide the seedlings. Reach into the open container or cut side flaps to slide them out. With the proper spacing, you can plant the entire block without dividing.

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