What to plant in December in Canada: by zone, from the Prairies to the coast

In Canada, planting in December depends heavily on your specific regional microclimate and hardiness zone. While coastal British Columbia gardeners can still sow winter greens under cover, growers in the frozen Prairies and interior provinces must transition to indoor propagation, winter sowing in milk jugs, and essential cold-season maintenance. Knowing what to plant during this coldest month requires matching your local frost patterns to the appropriate indoor or outdoor protection.

Understanding Canadian Hardiness Zones in December

To garden successfully in Canada, you must understand the Canadian Plant Hardiness Zone system. This system ranges from zone 0a in the far north to zone 9a on the mildest parts of Vancouver Island.

It is important to note that the Canadian system is not the USDA scale. While the USDA scale relies solely on minimum winter temperatures, the Canadian system integrates seven distinct climate variables. These variables include wind speed, maximum snow depth, rainfall, and the length of the frost-free period. Because of these factors, a Canadian zone designation provides a more comprehensive picture of winter survival for crops and perennial plants.

During December, the vast majority of Canada is locked in deep winter, meaning the ground is frozen solid. However, by using microclimates, indoor setups, and season extension tools, you can still keep your gardening year active. Understanding how your regional zone behaves during the winter solstice is the first step to planning your December activities. For those managing extreme cold, reviewing zone 2-4 gardening in Canada offers specific strategies for northern microclimates.

Zones 2 to 3: Prairies, Northern Ontario, Northern Quebec, and the Territories

In these ultra-cold regions, outdoor gardening is completely paused in December. Temperatures frequently drop below minus twenty degrees Celsius, and the soil is frozen deep into the ground. Sowing seeds directly outdoors is impossible, but there are still productive ways to grow food and prepare for spring.

1. Indoor microgreens and sprouts

• Varieties to grow: Pea shoots, sunflower shoots, radishes, broccoli, and mustard greens are ideal.
• Setup: Use shallow trays filled with a light, organic seed-starting mix. Place them on a bright south-facing windowsill, or use supplemental LED grow lights to compensate for the short December days.
• Harvest: Snip the greens at the soil line when the first set of true leaves begins to emerge, typically ten to fourteen days after sowing.

2. Winter sowing in milk jugs

• Technique: This method uses recycled plastic milk jugs as miniature greenhouses. Cut the jugs in half, add drainage holes to the bottom, fill them with moist potting soil, and sow seeds of native Canadian perennials or cold-hardy annuals.
• Placement: Tape the jugs closed and place them outside in a snowbank or protected spot. The seeds will remain dormant through the winter, undergoing natural cold stratification, and will germinate automatically as the soil warms in spring.
• Suitable crops: Native wildflowers, milkweed, and cold-tolerant herbs like lavender and echinacea. For more on managing these short-season environments, consult our guide on zone 3 gardening.

Zones 4 to 5: Interior Ontario, Southern Manitoba, and Interior Quebec

These zones experience classic, snowy Canadian winters. While the outdoor ground is frozen, gardeners in southern Manitoba, interior Ontario, and southern Quebec can utilize indoor spaces and protected structures to keep things growing.

1. Indoor culinary herbs

• Varieties: Chives, parsley, cilantro, and oregano can be grown in pots indoors.
• Care: Place pots in a room that stays between fifteen and twenty degrees Celsius. Ensure they receive at least six hours of bright light, or use a small grow light set on a twelve-hour timer. Water sparingly, as indoor air is dry but plant growth is slow.

2. Winter sowing under cover

• Setup: If you have an unheated greenhouse or a cold frame, you can sow cold-hardy winter greens in late autumn to harvest in December. However, sowing new seeds in December is generally not recommended in these zones because low light levels prevent germination.
• Maintenance: Keep existing winter crops in cold frames dry. High humidity combined with freezing temperatures causes mold and rot. For structural setups, explore our resource on season extension in Canada.

Zones 6 to 7: Southern Ontario, the Maritimes, and the Fraser Valley

These regions experience a slightly milder winter, though frost and snow are still regular occurrences in December. Gardeners here can push the boundaries of under-cover sowing and prepare early spring crops.

1. Cold frame salad greens

• Varieties: Spinach, claytonia (miner's lettuce), corn salad (mache), and winter-hardy lettuces.
• Method: Sow these seeds directly into the soil inside a cold frame or under a low polytunnel. While growth will be extremely slow due to the lack of daylight, the seeds will germinate and establish roots, giving you an exceptionally early spring harvest.
• Protection: Use heavy horticultural fleece inside the cold frame to provide a double layer of insulation on nights when temperatures drop significantly.

2. Indoor onion and leek starts

• Timing: While most gardeners wait until January or February, some growers in southern Ontario start slow-growing onions and leeks from seed indoors in late December.
• Setup: Sow seeds thickly in deep flats. They require a consistent temperature of twenty degrees Celsius to germinate, followed by bright light and cooler temperatures (around fifteen degrees Celsius) to prevent them from becoming spindly.

Zone 8: Coastal British Columbia

Coastal British Columbia has the mildest winter climate in Canada. Frosts occur, but the ground rarely freezes solid for extended periods, allowing for unique winter sowing opportunities.

1. Direct sowing under cloches

• Varieties: Broad beans (fava beans) and winter peas can be sown directly in early December.
• Method: Sow seeds five centimeters deep in well-drained soil. Protect the planting area with a cloche or a floating row cover to shield the soil from heavy winter rains, which can rot the seeds before they germinate.
• For regional specifics, consult our guide on when to plant vegetables in BC.

2. Overwintering salad crops

• Varieties: Arugula, mustard greens, kale, and winter spinach.
• Care: Sow these greens in cold frames or under simple plastic tunnels. Keep the soil moist but not waterlogged. Harvest outer leaves sparingly to allow the plants to continue growing slowly throughout the winter.

Essential December gardening jobs across Canada

Regardless of your hardiness zone, December is a critical month for protecting your soil, maintaining your equipment, and planning for the upcoming spring season.

1. Protecting soil and perennial beds

• Mulching: Apply a thick layer of straw, shredded leaves, or evergreen boughs over garlic beds and perennial vegetable plantings. This insulation prevents the soil from rapidly freezing and thawing, which can heave plants out of the ground.
• Soil coverage: Ensure no garden soil is left bare to the elements. Bare soil is vulnerable to erosion from wind and heavy winter rains. For complete steps on preparing your beds, read how to winterize your garden.

2. Maintaining winter tools and structures

• Snow removal: Heavy, wet snow can easily collapse polytunnels, greenhouse roofs, and cold frames. Keep a soft-bristled broom handy to gently clear snow accumulation after every major storm.
• Tool care: Clean, sharpen, and oil your hand tools before storing them for the winter. Use a wire brush to remove rust, sharpen blades with a whetstone, and apply a thin coat of mineral oil to prevent oxidation.

3. Seed inventory and ordering

• Germination testing: Check the viability of your leftover seeds by placing ten seeds between damp paper towels in a plastic bag. If fewer than seven seeds germinate after two weeks, discard the packet or sow it much more thickly in the spring.
• Planning: Draw a map of your garden beds to plan crop rotations. Ensure you do not plant crops from the same family (such as nightshades or brassicas) in the same spot two years in a row to prevent pest and disease buildup.