Seed Starting Schedule for Canadian Gardens

Seed Starting Schedule for Canadian Gardens

Starting seeds indoors is one of the most rewarding skills a Canadian gardener can develop. It saves money, gives you access to hundreds of varieties not found as transplants at garden centres, and lets you get a jump on our short growing season. This guide provides a week-by-week schedule based on a last frost date of May 24, which is typical for much of southern Ontario, the Ottawa valley, and southern Quebec. If your last frost date is earlier or later, simply shift the entire schedule accordingly.

Before You Start: Essential Setup

Gather your supplies before the first sowing date arrives:

• Grow lights: Full-spectrum LED shop lights are affordable and effective. Position them 5-10 cm above seedlings and run them 14-16 hours per day. A south-facing window alone is not enough in a Canadian winter; seedlings will be leggy and weak.
• Heat mats: Many seeds germinate faster at 21-27 C. A thermostat-controlled heat mat under your trays makes a significant difference for peppers, tomatoes, and eggplant.
• Seed-starting mix: Use a sterile, soilless mix of peat or coco coir, perlite, and vermiculite. Do not use garden soil or potting mix, which is too dense and may carry disease.
• Cell trays and pots: 72-cell trays for initial sowing, 10 cm (4 inch) pots for potting up. Reuse trays from previous years after washing with a dilute bleach solution.
• Labels and a notebook: Track sowing dates, varieties, and germination rates. This information is invaluable for planning future years.

The Schedule (Based on May 24 Last Frost)

Late February (12-13 Weeks Before Last Frost)

• Onions and leeks: These need the longest indoor growing period of any common vegetable. Sow thickly in a deep tray, keep under lights, and trim tops to 10 cm when they get floppy. Varieties like Ailsa Craig, Copra, and Cortland perform well across Canada.
• Celery and celeriac: Tiny seeds that need light to germinate. Press into the surface of moist mix, do not cover. Germination is slow (14-21 days) so be patient.

Early to Mid March (10-11 Weeks Before Last Frost)

• Peppers (hot and sweet): Peppers need warmth to germinate (27-30 C is ideal). Use a heat mat. Expect 10-14 days for germination. Varieties proven in Canada include Ace, King of the North, Hungarian Wax, and Early Jalapeno.
• Eggplant: Similar requirements to peppers. Start at the same time. Ichiban and Orient Express are reliable early producers.
• Artichokes: If you are adventurous, artichokes can be grown as annuals in Canada. Start now and vernalize (chill) seedlings for 10 days at 10 C before transplanting to trigger flower bud production.

Late March to Early April (7-8 Weeks Before Last Frost)

• Tomatoes: The most important sowing of the year for many Canadian gardeners. Sow 6-8 weeks before transplant date. For a May 24 last frost with transplanting around June 1, sow tomatoes between March 25 and April 7.
• Herbs (perennial): Parsley, thyme, oregano, sage, and chives are slow to germinate and benefit from an early start. Parsley can take 3-4 weeks to emerge; soaking seed overnight speeds it up.
• Head lettuce and radicchio: If you want full heads rather than loose leaf, start indoors now for transplanting out under row cover in late April.

Mid April (5-6 Weeks Before Last Frost)

• Brassicas (for spring planting): Broccoli, cauliflower, cabbage, Brussels sprouts, and kale. These are cold-hardy and can be transplanted outdoors 2-3 weeks before the last frost date. Sow now for transplanting around May 10.
• Swiss chard: Sow in cell trays. Chard transplants well and tolerates light frost once hardened off.
• Annual herbs: Basil, cilantro, and dill can be started now, though dill and cilantro also direct-sow well. Basil is frost-sensitive and should not go out until after the last frost.

Late April to Early May (3-4 Weeks Before Last Frost)

• Cucumbers, squash, and melons: These grow fast and resent root disturbance. Sow in 10 cm peat pots or soil blocks 3-4 weeks before transplanting. Do not start too early or plants become rootbound and stunted.
• Zucchini and pumpkins: Same timing as cucumbers. These large-seeded crops germinate quickly (5-7 days) in warm conditions.

Direct Sowing Outdoors

Not everything needs to start indoors. These crops do best sown directly in the garden:

Early Spring (As Soon as Soil Can Be Worked, Late April)

• Peas: Sow as soon as soil reaches 5 C. Peas tolerate frost and actually prefer cool conditions. Sow every 2 weeks until mid-May for an extended harvest.
• Spinach: Direct sow in early spring and again in late August for a fall crop. Spinach bolts quickly in summer heat.
• Radishes: Ready in 25-30 days. Sow small batches every 10 days from late April through May.
• Lettuce and mesclun mixes: Sow thickly and thin as you harvest baby greens.
• Carrots: Sow 2-3 weeks before last frost. Germination is slow (14-21 days), so mark your rows and keep the soil moist. Mix seed with sand for more even distribution.

After Last Frost (Late May to Early June)

• Beans (bush and pole): Wait until soil is at least 16 C. Beans sown in cold soil rot before germinating. In most of Canada, early June is the sweet spot.
• Corn: Needs warm soil (18 C minimum) and a long season. Sow in blocks of at least 4 rows for pollination. Early varieties like Peaches and Cream and Bodacious work in Zone 5.
• Direct-sow squash and pumpkins: If you did not start these indoors, sow directly once soil hits 18 C. Lay black plastic mulch over the planting area a week before sowing to warm the soil faster.

Common Canadian Seed Starting Mistakes

1. Starting too early. This is the most common mistake. Tomato seedlings started in February will be leggy, rootbound, and stressed by the time they can go outside. Follow the schedule.
2. Insufficient light. Windowsills produce weak, stretched seedlings. Invest in proper grow lights.
3. Skipping hardening off. Moving pampered indoor seedlings directly into the garden results in transplant shock, sunburn, and often death. Take 7-10 days to gradually acclimate plants to outdoor conditions.
4. Overwatering. Soggy soil causes damping off, a fungal disease that kills seedlings at the soil line overnight. Let the surface dry slightly between waterings and ensure trays have drainage.
5. Not potting up. Seedlings left in small cells too long become rootbound. Move to larger pots when roots fill the cell, typically 2-3 weeks after germination for fast growers.

Succession Planting: Keep the Harvest Coming

Do not sow everything at once. Stagger your plantings for a continuous harvest:

• Lettuce and greens: Sow new rows every 2-3 weeks from April through August.
• Beans: Sow every 3 weeks from early June to mid-July.
• Brassicas: Start a second round of broccoli, cabbage, and kale indoors in June for fall harvest. Fall brassicas are often sweeter than spring ones, as light frost improves their flavour.
• Carrots and beets: Sow a late crop in mid-June to early July for fall harvest and storage.

Adjusting for Your Region

Canada is vast, and growing conditions vary enormously:

• Vancouver and coastal BC (Zone 8): Shift the entire schedule 4-6 weeks earlier. You can often direct-sow peas in February and transplant tomatoes in early May.
• Prairies (Zones 2-3): Shift 2-3 weeks later. Last frost may not pass until early June. Choose the earliest maturing varieties available.
• Atlantic provinces (Zones 5-6): Similar to southern Ontario timing, but cooler summers mean focusing on cool-season crops and early tomato varieties.
• Northern Ontario and Quebec (Zones 3-4): Shift 2-4 weeks later and invest heavily in season extension (row cover, cold frames, unheated greenhouses).

Keep records of what you sow, when, and how it performs. After 2-3 seasons you will have a custom schedule perfectly tuned to your specific garden, microclimate, and growing goals.