9 Pros and Cons of Winter Sowing

Considering winter sowing to simplify seed-starting this season? Now is the time to get going. The easy and rewarding method is full of advantages and yields sturdy seedlings. Garden expert Katherine Rowe explores the merits and potential variables of winter sowing.

Small lettuce seedlings growing in soil-filled compartments of a clear plastic container, with plant markers labeled for identification.

Contents

Winter sowing gives seedlings a jumpstart on warm-season growing. Sowing in winter refers both to direct sowing, even in snow, and to seeding outdoors in mini homemade “greenhouses” for insulation. Direct sowing is the easiest seed-starting technique and is good for hardy selections that require cold stratification to germinate. Here, we’ll focus on the advantages of the homemade greenhouse method, using repurposed containers to develop robust seedlings. The pros and cons of both winter sowing means are similar.

Winter sowing in containers allows exposure to natural elements, where seeds work with nature to germinate as conditions are most suitable. With exposure, seedlings develop sturdy roots for easy transplanting with no hardening-off period necessary.

The streamlined seed-starting technique uses basic household supplies, making it resourceful, budget-friendly, and accessible to get growing early. It also saves indoor growing space and time spent managing seedlings in a controlled environment. Now is the time to winter sow, ideal for cold climates. Its many advantages outweigh the variables, but it’s helpful to know what to watch for when choosing a seed-starting method.

What is Winter Sowing?

A single translucent plastic milk jug with a cut hole, placed on soil, used as a mini greenhouse to protect a young plant.
A makeshift mini-greenhouse protects them from cold temperatures and winds.

Winter sowing mirrors natural conditions by placing seeds outside in exposed situations while offering insulation. The technique provides the essential elements seedlings need to sprout: oxygen, light, water, and temperature variation. A makeshift mini-greenhouse protects them from cold temperatures and winds. Seedlings sprout when the weather warms and conditions are favorable. 

Pro: Resourceful and Economical

Several white translucent milk jugs cut in half and filled with soil and seeds.
To use milk jugs as an easy example, you’ll remove the cap and cut the jug in half, almost all the way around.

Winter sowing is cost-effective, doesn’t take up indoor space, and allows us to sow earlier for seedlings that take off as temperatures warm. You can repurpose almost any clear plastic container to become a growing vessel. Basic supplies include:

  • Clear or transparent containers like milk jugs and water bottles 
  • High-quality potting soil
  • Screwdriver or drill to poke drainage holes
  • Scissors and tape to modify the container

Start with clear and very transparent containers like milk jugs, plastic bottles, salad green clamshells, or freezer bags. Make four to six holes in the base to ensure good drainage. To use milk jugs as an easy example, you’ll remove the cap and cut the jug in half, almost all the way around. Leave the handle in place to lift the lid. Fill the jug with four inches of potting mix. Sow seeds according to packet guidelines and water them in. Tape the cut seam to retain moisture. 

Place the little greenhouses in a sunny spot exposed to the elements – snow and rain are fine. The seeds benefit, and seedlings harden off in the natural conditions as they sprout later in the season.

Con: Relies on Natural Conditions

Close-up of young seedlings of Chard plants in starting trays under LED lamps. Chard plants are characterized by their large, glossy, and deeply veined leaves that grow in a dense rosette. The leaves come in bright green with contrasting yellow and purple veins and stems.
Heat mats, cell packs, and grow lights let us tailor specific requirements for germination.

One of the beauties of winter sowing is that it relies on outdoor elements to produce healthy seedlings. This reliance also brings a lot of variability to the process. In more controlled situations like indoor seeding, supplies like heat mats, cell packs, and grow lights let us tailor specific requirements for germination. Indoors, we’re able to hone in on moisture and placement more accurately than in a more naturalized setting. 

Winter sowing is a more generalistic approach, which is bit of an experiment each season because we can’t control the weather. With more practice, timing and siting evolve. Place containers in a sunny location (south or east-facing) with access to natural moisture.

Pro: Low Maintenance

A hand lifting young Romaine lettuce plants with visible roots from dark soil, showing green leaves and red stems.
Divide each for planting in its permanent growing location.

Other than direct-sowing in the landscape, protective winter sowing is as easy as can be. While it does take preparation of materials and oversight throughout the season, it’s a nearly effortless process to start. Letting nature do the work for us means less time intensively managing little seedlings in an indoor environment with its own variables. 

Seeds started indoors benefit from a hardening-off period to gradually introduce them to their garden environs. Winter-sown seedlings experience this as they develop. Direct-sown seeds need no hardening off, either, but are often slower to develop than those started in protective containers. 

Transplanting is easy as you lift the lid or cut side panels to slide seedlings out of their greenhouses. Divide each for planting in its permanent growing location.

Con: Out of Sight, Out of Mind

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.
Close the lids before nightfall’s dropping temperatures.

To counterbalance low maintenance and oversight is the potential to forget to check the containers regularly. Even when seeds haven’t yet germinated, it’s important to keep soils evenly moist. Visible condensation is a good sign; it means there’s plenty of moisture available in the jug. Good drainage is essential to keeping fungal problems like rot at bay. 

Maintain soil moisture and check containers weekly. With regular rain or snow, the vessels likely need only supplemental water or misting every few weeks. Watering may increase as temperatures warm and seedlings sprout. 

On warm days, open the lid for ventilation. Airflow is important, too, in staving off disease problems and for transpiration. Remember to close them up before nightfall’s dropping temperatures.

Keep an eye on high winds and stabilizing the vessels so they don’t topple over. Situate them near a wall or the foundation or in crates or trays if wind is an issue. Some wind is good for seedlings to develop strong stems, but disrupting their situation can be detrimental.

Pro: Allows Cold Stratification

Close-up of elderly hands planting tiny pale yellow seeds into a peat starter tray filled with soil, surrounded by small clay pots, some holding houseplants.
Sow seeds about six to eight weeks before you would typically transplant them into the garden.

As early as December and 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 selection. Many seeds that overwinter are often native perennials or annuals that naturally self-sow in the landscape. But winter sowing is not limited to those selections; you can use it for most seeds.

Climate and temperature affect the process, and freezing conditions offer a prime time to begin. Cold weather ensures the stratification period while staving off germination until conditions are consistently temperate.

Sow seeds about six to eight weeks before you would typically transplant them into the garden. In cold climates, this can extend into February and March; in warm climates, seeds may germinate faster.

Con: Subject to Early Germination and Freezing

Gardener sowing tomato seeds in trays on a lawn, planting two seeds per cell.
Tomatoes are frost-sensitive and develop later in the season under warm air and soil temperatures. 

Because the situation is outdoors in the elements, weather fluctuations have a bearing. If your climate has a warm spell that allows for germination, followed by an extended cold snap, sprouts risk freezing. 

Starting in cold conditions allows natural freeze and thaw cycles that some seeds require. Cold temps ensure seedlings won’t sprout too early, only to risk freezing at the next cold snap. But if your area experiences drastic fluctuations between warm and cold days, wait a month or so to sow tender annuals like tomatoes, peppers, and zinnias. These are frost-sensitive and develop later in the season under warm air and soil temperatures. 

If you’re up for experimenting, sow a round all at once (frost-sensitive along with the hardy perennials and annuals) and a later round of the sensitive selections for comparison. An early and late round better ensure germination in either case, and you can note which worked moving forward.

Pro: Works for Most Seeds

A group of white pumpkin seeds resting on loose, dark brown soil, ready for planting.
Cucumbers are best direct-sown to avoid disturbance.

Winter sowing is versatile for most home garden seeding, including herbs, vegetables, flowering annuals, and perennials. Particularly reliable are cold hardy perennials. As mentioned, these are often the ones who depend on cold stratification and naturally self-seed. Winter sowing gives them a headstart on development to extend the season and for earlier flowering and fruiting.

Frost-tolerant annuals and vegetables that thrive in the cool season are other durable options. Petunias, snapdragons, viola, calendula, hollyhock, spinach, broccoli, cabbage, and kale (Brassica species) enjoy cool spring conditions. They handle frost and move easily from the container to the bed or pot. Herbs, too, do well with winter sowing.

A fun component of this method is trialing different types of seeds. Those with sensitive roots at transplanting (root vegetables, cucumbers, larkspur, lupines, poppies) are best direct-sown to avoid disturbance. It’s possible to winter sow some with root sensitivities, just like starting them indoors, with care at removal.

Con: Germination Times May Vary

Three biodegradable pots with young tomato seedlings emerging from light brown soil, placed on a black tray.
Some perennials, like milkweed and columbine, have long germination times and may emerge later than others

As the weather is a factor in suitability for germination, so is the average germination length for a given species. Experiment by starting all your warm-season selections at the same time, or hold off until February or March for heat-loving plants (zinnias, tomatoes, peppers, eggplants, squash, 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. They may still be viable in their jugs. Leave them in place for a few weeks, staying on the lookout for seedlings, moisture control, and ventilation. Make a note of what was successful and what showed lesser germination rates for the next round the following season.

Pro: Yields Hardy Seedlings

Gloved hands using a small trowel to plant marigold seedlings with green leaves and yellow flowers into prepared soil.
When they develop true leaves and the appropriate height, move them to their permanent growing spots

On par with the advantages of economy, resourcefulness, and low maintenance is the productivity of winter sowing. Seedlings that develop in these situations have strong roots and leafy uppers. They’re ready to transplant after exposure to warm days with the “hood” open on their containers. Follow regular transplant guidelines for air and soil temps for installation. Quick growth ensues as they have a headstart beyond indoor and direct-sown seeds.

When they develop true leaves and the appropriate height, move them to their permanent growing spots or pot them up to larger containers to continue developing. Keep pots outdoors in a similar environment to their sowing as they continue to grow. The exception is to monitor sun exposure. Containers that may have been south-facing in the winter may receive too much strong sunlight for tender seedlings, especially in warm climates. Move these to an east-facing spot if possible or to an area that receives afternoon protection.

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