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

March planting in Canada varies by region: gardeners in cold northern zones focus on indoor seed sowing, while coastal growers begin direct outdoor planting. In central and eastern Canada, March is the time to start slow-growing crops indoors and prepare cold frames for early spring greens. Success depends on working within your specific regional frost dates rather than following a single national schedule.

March is a month of extreme contrast across Canada. While coastal British Columbia experiences the first signs of spring with emerging perennials, the Prairies and northern regions remain locked in deep winter snow. Attempting to apply a single planting guide to the entire country leads to failed crops and wasted seeds.

To plant successfully, Canadian gardeners must use the Canadian Plant Hardiness Zone system. Developed by Natural Resources Canada, this system is distinct from the USDA scale because it incorporates multiple climate variables: minimum winter temperatures, frost-free days, rainfall, wind, and snow cover. Understanding your local zone and average last spring frost date is the most reliable way to plan your March gardening activities.

By organizing your sowing tasks by Canadian zone bands, you can ensure that indoor seedlings do not become leggy before transplanting, and outdoor seeds do not rot in cold, waterlogged soil.

Understanding Canadian planting zones in March

The Canadian hardiness scale ranges from zone 0a in the far north to zone 9a on Vancouver Island. In March, these zones dictate whether you are working with indoor grow lights, unheated greenhouses, or outdoor soil.

When planning your spring garden, consult a reliable regional guide such as the Ontario planting zones reference to identify your exact local frost window. Across the country, March tasks are split between indoor seed starting, cold frame management, and early outdoor direct sowing.

Zones 2 and 3: Sowing slow-growing crops indoors

In the Canadian Prairies, northern Ontario, northern Quebec, and the territories, outdoor soils remain frozen deep into spring. The last frost in these regions often occurs in late May or early June. Planting in March is exclusively an indoor activity focused on crops that require a long head start to mature during the short summer.

For gardeners practicing zone 3 gardening, March is the time to start seeds that take up to twelve weeks of indoor growth before they can be safely transplanted outside.

1. Onions and leeks

Sow onion and leek seeds in early March. These crops are slow to develop from seed and require a long period of indoor growth to form sturdy transplants. Sow the seeds 1 cm deep in flat trays filled with pre-moistened seed-starting mix. Keep the soil temperature around 21°C until germination occurs, then move the trays to a cool, bright window or under grow lights.

2. Celery and celeriac

Celery and celeriac require up to ten weeks indoors before the last frost. Because the seeds are tiny and require light to germinate, surface-sow them on top of the soil and press them down gently without covering them. Keep the soil consistently moist by misting it with water and covering the tray with a clear plastic dome.

Zones 4 and 5: Starting the indoor seedling shelves

Zones 4 and 5 cover interior Ontario, southern Quebec, and parts of the southern Prairies. In these regions, the last spring frost typically occurs in mid-to-late May. March is the peak period for initiating the indoor sowing cycle for warm-season vegetables that need a moderate head start.

To determine the exact timing for these starts, review the guidelines on when to start seeds indoors in Canada to prevent seedlings from outgrowing their pots before outdoor temperatures warm.

1. Peppers and eggplants

Sow peppers and eggplants in mid-to-late March. These heat-loving crops require consistent soil temperatures between 24°C and 29°C to germinate successfully. Use an electric seedling heat mat under your seed trays to maintain this warmth. Once the seeds sprout, move them immediately under bright grow lights to prevent the stems from stretching.

2. Early brassicas

Sow cabbage, broccoli, cauliflower, and kale in late March. These cool-season crops can tolerate light frosts after they are transplanted outdoors, meaning they can go into the ground in late April or early May. Starting them in cell packs in March ensures they are large enough to handle the transition.

3. Hardy herbs

Sow parsley, thyme, oregano, and rosemary indoors. Rosemary and parsley are notoriously slow to germinate, often taking up to three weeks to show signs of life. Sowing them in March ensures you have strong herb starts ready for the spring garden.

Zones 6 and 7: Transitioning to the cold frame

Zones 6 and 7 include southern Ontario, the Niagara Peninsula, coastal sections of the Maritimes, and the Fraser Valley of British Columbia. Here, spring arrives earlier, with last frost dates falling in late April or early May. Gardeners in these areas can begin utilizing unheated structures for season extension in Canada to buffer young plants against cold spring nights.

1. Tomatoes

Sow tomatoes indoors in mid-March. Starting them now ensures they are ready for transplanting under protection in May. Choose short-season varieties that perform well in Canadian climates, keeping the soil warm until germination and then providing maximum light.

2. Spinach and hardy salad greens

Sow spinach, lettuce, arugula, and other greens inside cold frames or unheated polytunnels. These greens can tolerate cold temperatures and will germinate in soil as cool as 5°C. Utilizing a cold frame in March provides protection from heavy spring rains and biting winds, allowing for an early harvest of salad greens in late April.

3. Broad beans

Sow broad beans in deep modular trays or root trainers inside an unheated greenhouse or cold frame. Broad beans develop deep root systems and do not tolerate root disturbance well. Starting them in deep cells in March allows you to plant sturdy, established seedlings into the ground as soon as the soil is workable.

Zone 8: Coastal British Columbia's early outdoor season

Coastal British Columbia enjoys the mildest winter climate in Canada, with last frosts often occurring in late March or early April. Gardeners in this zone can begin direct outdoor sowing of hardy crops in March, provided the soil is not waterlogged.

When planning your outdoor beds on the coast, consult the guide on when to plant vegetables in BC to balance the coastal rain patterns with soil temperature requirements.

1. Peas

Direct-sow shelling peas, snap peas, and snow peas in early-to-mid March. Peas thrive in cool, moist spring weather. Sow the seeds 2 cm deep and 5 cm apart along a trellis or support structure. If the soil is exceptionally wet, sow them in raised beds to prevent the seeds from rotting in standing water.

2. Garlic and shallots

If you missed the autumn planting window, plant garlic cloves and shallot sets as early in March as the soil can be worked. While autumn planting is ideal for maximum bulb size, early spring planting still yields a respectable harvest of smaller bulbs or green garlic.

3. Radishes and early carrots

Direct-sow radishes and early Nantes carrots in late March. Radishes are fast-growing crops that can be harvested in less than a month, making them excellent for sowing between slower-growing crops. Sow carrot seeds in shallow drills 1 cm deep, keeping the soil moist until germination.

Essential March gardening jobs across Canada

Regardless of your specific hardiness zone, March is a critical month for preparing your tools, soils, and structures for the busy growing season ahead.

1. Setting up indoor seed-starting equipment

Before sowing your first tray, clean and sanitize all seed flats, pots, and domes to prevent damping-off disease. Wash them in a solution of nine parts water to one part household bleach, then rinse thoroughly. Test your grow lights, replace old fluorescent tubes, and ensure your seedling heat mats are functioning correctly.

2. Soil warming and bed preparation

In zones 5 to 7, you can accelerate the outdoor planting window by warming the soil artificially. Cover your outdoor vegetable beds with clear or black plastic sheeting in early March. This traps solar radiation, raises soil temperatures by several degrees, and sheds heavy spring rain, leaving the soil dry and workable sooner.

3. Pruning fruit trees and shrubs

March is the ideal time to prune deciduous fruit trees, grapevines, and berry bushes while they are still dormant. Remove dead, damaged, and diseased wood. Pruning during dormancy minimizes the risk of disease transmission and encourages vigorous new growth in the spring.