5 Essential Winter Sowing Supplies and Equipment

Now is the time for winter sowing - an easy, resourceful, rewarding way to start seeds working with nature. Using simple containers for homemade “greenhouses,” strong seedlings emerge, ready for transplanting. With a few essentials and repurposed household supplies, we’ll be on our way to (nearly) effortless seed-starting. Join gardening expert Katherine Rowe in all that’s needed for this streamlined approach to seeding.

Written by Katherine Rowe Horticulture review by Sarah Jay Last updated: January 11, 2025 | 6 min read

Close-up of winter sowing supplies, featuring a row of white plastic milk jugs repurposed as seed containers, arranged against the wall of a house in a snowy winter garden with patches of green grass.

Contents

Winter sowing is a productive, uncomplicated way to get a headstart on spring planting with simple household supplies. Seeds sown in insulated containers outdoors develop as conditions naturally suit their germination. Seedlings in their homemade mini-greenhouses are often stronger with more established roots, earlier flowering and fruiting, and don’t need hardening off before transplanting.

Winter sowing is resourceful and economical and requires little effort to start seeds. It saves precious indoor growing space and the need for intensive management. You can repurpose materials on hand, get creative in the setup, and then wait until temperatures warm for seedlings to sprout. Now is the time to gather your supplies and winter sow, even in the snow! With a few essentials, seed-starting gets underway in short order.

What is Winter Sowing?

In a snow-covered garden, rows of milk jugs repurposed as mini greenhouses sit neatly, aiding in germinating seeds during winter. — Mimicking nature, this technique boosts early seedling growth.

The premise of winter sowing is to mimic natural conditions. The technique provides the basic elements seedlings need to sprout: oxygen, light, water, and temperature variation. Seedlings start outdoors in a protected environment over the winter. A mini-greenhouse situation protects them from cold temperatures while exposing them to garden conditions. They sprout when temperatures warm and conditions are favorable.

Winter sowing is cost-effective because it uses mostly recycled supplies like plastic jugs. It doesn’t take up space like indoor seed-starting, and allows us to sow earlier for seedlings that take off as temperatures warm.

When to Winter Sow

Close-up of male hands carefully pouring seeds from a packet into his palm, preparing to sow them into a plastic bottle filled with soil, against a softly blurred background. — Perfect timing ensures seedlings sprout when temperatures warm.

Climate and temperature affect winter sowing, and a great time to start is in freezing conditions. This ensures seedlings won’t sprout too early, only to risk freezing at the next cold snap. Those that need it, including many hardy perennials, receive their cold stratification period.

Sow seeds about eight weeks before you would typically transplant them into the garden. January is the time to winter sow seeds that benefit from cold stratification (and even into February and March in cold climates). In warm climates, seeds may germinate faster.

If your climate experiences drastic fluctuations of freeze and thawing, wait a month or so on tender annuals like tomatoes and zinnias.

Basic Supplies

Several white plastic jugs, partially cut and half-filled with soil, arranged as mini greenhouses for seed sowing. — Use clear containers, soil, and water for easy seedling success.

One of the big advantages of winter sowing (in addition to strong seedlings) is that it doesn’t call for specialized seed-starting supplies or equipment. The basics are a clear container, soil, seeds, and water. We’ll dive into how to prep the containers and seed selection below.

In addition to the container, you’ll need:

Poly or duct tape if using milk jugs or soda bottles
Scissors or a sharp knife
Clothes pins if using freezer bags
A screwdriver, drill, or utility knife to poke holes for drainage
Potting soil
Seeds
Water
Permanent marker for labeling

Seeds to Winter Sow

Close-up of a man's hands carefully sowing seeds into a large plastic bottle, half-filled with potting mix, featuring ventilation holes cut into its sides. — Start hardy plants early for vibrant gardens later on.

As early as January, you can winter sow many selections, especially those that are hardy or need cold stratification to germinate. Cold stratification is a period of several weeks at temperatures around 40°F (4°C), depending on the plant. These enjoy time outside in the winter and are often native perennials that naturally self-sow in the landscape. But winter sowing works for just about anything!

Hardy perennials are reliable, as are frost-tolerant annuals and vegetables that thrive in the cool season. Petunias, snapdragons, calendula, hollyhock, spinach, broccoli, cabbage, and kale (Brassica species) enjoy cool spring conditions. Perennials, annuals, and herbs that self-sow or reseed are good contenders.

Experiment by starting all your warm-season selections at the same time, or hold off until February for heat-loving plants like zinnias, tomatoes, peppers, eggplants, squash, and ground cherries that develop later in the season. Some perennials, like milkweed and columbine, have long germination times and may emerge later than others, depending on your climate. Don’t give up on those that don’t sprout in time with the others.

Potting Mix

Male hands wearing orange and black gloves thoroughly mix potting soil in a black plastic tray placed on a table. — Use quality potting mix for the best seedling growth.

No special seed mixes or formulated growing mediums are necessary for winter sowing. Use a high-quality potting mix (not garden soil, which is too dense). The mix should be light and fluffy with good aeration, drainage, and moisture retention, but not with moisture control or added fertilizers.

To mimic the seed’s natural garden environment, good drainage, and even moisture are the keys to success.

Clear Containers

Close-up of tiny green sprouts growing in a clear plastic salad container with soil, its lid open, and wooden sticks marking the seed names. — Transparent containers with drainage help seedlings thrive outdoors.

Start with clear or very transparent containers like milk jugs, plastic bottles, bins, or baggies. Anything that allows light to penetrate with the capacity for drainage, ventilation, a few inches of soil, and room for seedling growth works well. Clean the containers in warm, soapy water to sanitize them for seeding.

Since the vessels will be outside, they’ll collect seasonal moisture from snow and rainfall. Create drainage holes – essential to prevent rot or fungal problems – by making four to six holes in the base. Use a permanent marker to label and date the seeds by container.

As temperature variations initiate germination, the container modifications allow for opening and closing for airflow and temperature regulation. When ready for transplanting, cut flaps in the containers to slide the seedlings out or reach in to divide them for planting in their garden locations.

We’ll cover a few of the most popular containers, but the simple prep applies to others you have handy. Additional translucent options include:

Salad greens packaging
Deli tray/cake/cookie container
Large takeout containers

Milk Jugs

For milk jugs, remove the cap and cut the jug nearly in half just below the handle, almost all the way around. Leave the handle in place as a means to lift the lid during the season. The open top 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 bottom. Sow seeds according to the depth and spacing of the packet guidelines, covering them lightly or gently pressing them for soil contact. 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. — Recycled soda bottles provide perfect mini-greenhouse conditions.

Two-liter soda or water bottles make cheap winter sowing supplies as well. 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 for soil and seedling growth.

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

Freezer Bags

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 in for evenly moist potting media.

Leave an inch or so of the seal open at the top of the bag for ventilation. To adjust airflow and temperature regulation 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. Use clothes pins to prop them open as necessary.

Bins

Two large clear plastic containers hold multiple red plastic pots with sown seeds, placed outdoors in a garden setting. — Plastic bins work as both trays and seedling support.

Clear plastic bins either hold the other vessels for support or become seedling trays themselves. Add a few inches of soil to the base, or use little solo cups or paper towel tubes cut into pieces to house the individual seedlings. Peirce holes in the lid for ventilation, popping it off to vent in late winter’s warming days.

Water and Ventilation

A gardener sprays mist onto large plastic bottles filled with soil and sown seeds using a spray bottle. — Mist seedlings if soil shows signs of drying out.

More often than not, natural moisture from snow, rain, and condensation is enough to maintain soil moisture. Check containers once a week or so, especially as conditions become dry or warm. If the soil surface shows signs of drying, mist or sprinkle with water to prevent shallow roots from drying.

Condensation is a good 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.

As spring approaches and seedlings sprout, vent the lid on warm, sunny days to allow natural transpiration. Close it up before temperatures drop late in the day. This is a natural hardening-off step that makes for easy planting without transplant shock.

Outdoor Placement

Close-up of young seedlings sprouting in plastic bottles filled with soil, basking in the sunlight in a garden. — Place containers in a sunny spot for optimal growth.

No matter which winter sowing supplies you choose, be sure to place the little greenhouses in a sunny spot where they’ll receive moisture. Expose them to the elements, even snow. The seeds benefit, and seedlings harden off in the natural conditions 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 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 or sided tray or tub.

As temperatures warm and seedlings germinate, open the containers for daytime ventilation. Close them before evening for protection against cold nights.