Winter sowing seeds

Winter sowing of seeds is a horticultural method in which gardeners plant seeds outdoors (usually in some form of protective container) during the colder months.

Seedlings being hardened through a winter sowing process, image by cristina.sanvito, cc.

This allows them to take advantage of the natural processes that occur within seeds in response to the environment. This can greatly benefit germination in the coming spring.

Instead of the more common method of sowing seeds indoors (or in a heated greenhouse), and then transplanting them outside, this method makes use of the cycle of seasons to foster healthy, robust plants.

The strategy often involves creating 'mini-greenhouses' made from recycled containers, such as Milk jugs and glass jars.

These winter sowing containers help to protect seeds from harsh winter weather, while still exposing them to the cold period required to break seed dormancy. The process known as stratification.

This winter sowing seeds method is especially beneficial for gardeners with limited indoor sowing space.

It is also cost-effective as it greatly reduces the need for specialized indoor equipment.

As the winter season wanes, the seeds will sprout at a time suitable to the local climate.

This will lead to plants that are better adapted to their outdoor environment. Helping to create a lush, vibrant garden upon the arrival of spring.

When to start winter sowing

The best time to start winter sowing will depend on your geographical location, and on the specific needs of the seeds you are sowing.

Usually, winter sowing is started anytime from late fall to mid-winter. Here's a seasonal guide to help you plan your winter sowing:

Late Fall/Autumn (Late October to early December)

Cool-Climate Regions: Start sowing perennials and hardy annuals that require a long period of cold stratification. Seeds to consider sowing include Winter Aconite (Eranthis hyemalis) and Snowdrops (Galanthus nivalis). Hardneck varieties of Garlic and winter onions can also be planted at this time.

early season blooming snowflower plant
Early season color from snowdrops, photograph by Amanda Slater, CC.

Warm-Climate Regions: This is a suitable time to start sowing plants for regions that experience milder winters. Seeds to consider sowing include vegetables such as growing Lettuce and Carrots. Some flowering plants to try include Sweet peas and Pansies.

Early to Mid-Winter (January to February)

Cool-Climate Regions: At this time of year, you can continue to sow hardy perennials and also start sowing cool-season vegetables such as Broccoli and Brussels sprouts. Flowers to consider include Hellebores and the deciduous flowering shrub witch hazel (Hamamelis).

Warm-Climate Regions: Winter sowing can now include more varieties of vegetables, herbs, and flowers, as the risk of extreme cold diminishes. Consider plants such as peas, Snapdragons (Antirrhinum majus), Calendula (Calendula officinalis), and Sweet Alyssum (Lobularia maritima).

Late Winter to Early Spring (February to March)

Cool-Climate Regions: Time to sow semi-hardy plants, and more varieties of vegetables and herbs. Plants to consider sowing include Poppies (Papaver), Spinach (Spinacia oleracea), tomato plants, peppers, and Parsley (Petroselinum crispum).

Warm-Climate Regions: Start sowing warm-season crops as the temperatures start to rise. Try sowing plants such as Okra, Eggplant, Marigolds (Tagetes), Zinnia, and Sunflowers.

Remember, that the objective of winter sowing is to allow the seeds to undergo a natural process of cold stratification.

The cold temperature will help to break the dormancy of the seeds, preparing them for germination as temperatures warm up in the spring.

A Few Tips for Successful Winter Sowing

Well-Draining Soil: Soil should have good drainage to prevent the occurrence of waterlogging and root rot during the wet winter months.

Mulching: Mulch the soil with organic matter to provide insulation and protect plants from extreme cold.

Winter Covers: If not growing in containers, use row covers or cloches to protect the young plants from harsh winter conditions, if necessary.

Location: Place the containers in a part of the garden where plants can receive sufficient sunlight.

No-transplant winter sowing

No-transplant winter sowing involves sowing seeds directly outdoors in winter, allowing them to grow in place without later transplantation.

This can greatly increase success when growing plants that are known not to transplant well (as they are able to develop a healthy root system in situ).

Some plants that will benefit from a no-transplant winter seed sowing technique include vegetables such as Radishes, Peas, Dill, Cucumbers (sensitive roots); and Carrots and parsnips (long taproots).

As flowers such as Morning Glories (Ipomoea purpurea) and sunflowers have long taproots, transplanting them may lead to stunted growth. Likewise, the taproots of Larkspur (Consolida) are too delicate for transplanting.

Other flowers with delicate root systems include Nasturtiums (Tropaeolum majus) and California Poppies (Eschscholzia californica).

It is not usually a good idea to transplant Nasturtiums as they have a delicate root system. Photograph by Jennifer Rafieyan; CC.

For this method, choose hardy seeds and prepare the soil or containers with drainage holes.

Scatter seeds on the soil surface, lightly cover with soil or compost, and water lightly. Be sure to label the sowing areas for easy identification later.

It is important to protect seeds with either mulch or a transparent cover.

Once the seeds have undergone natural stratification in cold temperatures they will start to germinate.

As they grow stronger it is best to thin out the seedlings to prevent overcrowding.

This winter sowing seeds methodology will help to promote robust root growth and will also help to avoid the transplant shock that can occur when starting off seeds indoors.