What to Plant in May in Canada | Zone 5 & 6 Planting Guide

May is the busiest month in the Canadian vegetable garden. Soil temperatures finally climb above 10°C, last frost dates pass for most of zone 5 and 6, and the race to maximize your growing season begins in earnest. If you plant too early you risk frost damage; if you wait too long you lose weeks of production.

This guide breaks down exactly what to plant in May across Canadian zones 5 and 6 — what goes in the ground when, what still needs to wait, and how to sequence your plantings for continuous harvests.

Use the MyGardenPlanner.ca calculator to get planting dates customized for your exact zone and location.

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Know Your Last Frost Date First

May planting in Canada is zone-dependent. Here's a quick reference:

Cool-season crops (lettuce, peas, kale) can go out 2–4 weeks before last frost. Warm-season crops (tomatoes, peppers, squash) need to wait until after last frost — or be protected with row covers.

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Early May (May 1–15): Cool Season Crops & First Transplants

Direct Sow Outdoors

These crops tolerate light frost and can go in the ground now across most of zones 5–6:

Peas — If you haven't planted yet, get peas in the ground immediately. They struggle in summer heat; early May is your last good window for a spring crop. Sow 2.5 cm deep, 5 cm apart in double rows.

Lettuce & Salad Greens — Direct sow every 2 weeks through May for continuous harvests. Thin to 20 cm for heading types, 10 cm for loose-leaf.

Spinach — Bolt-tolerant varieties (Space, Tyee) can be direct sown now. Bolts quickly in heat — succession sow every 10 days and switch to fall spinach in August.

Radishes — 3–4 week harvest means you can sow now and be eating before tomatoes are even transplanted. Sow every 10 days.

Kale & Swiss Chard — Hardy enough for May temperatures across zones 5–6. Direct sow or transplant starts now.

Beets — Sow now for summer harvest. Pre-soak seeds 4–6 hours to improve germination. Thin to 8–10 cm.

Carrots — Direct sow when soil is consistently above 7°C. Keep seedbed moist for 2 weeks — carrots are slow to germinate and prone to drying out.

Zone 6 Early Transplants (May 1–10)

If you're in zone 6a or 6b and last frost has passed:

Broccoli, Cabbage, Cauliflower — Transplant hardened-off starts outdoors. These brassicas prefer cool soil and will struggle if transplanted too late.

Onion Sets & Transplants — Get onions in the ground early May for full-sized bulbs by harvest. Sets go 2–3 cm deep, 10 cm apart.

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Mid-May (May 10–20): Transition to Warm Season

Zone 5 Tender Transplants (After Last Frost)

Tomatoes — Wait until after your last frost date and soil has warmed to at least 15°C at root depth. Transplant on a cloudy day or late afternoon to reduce transplant shock. See the full tomato transplanting guide for zone-by-zone timing.

Peppers — Peppers need warmer conditions than tomatoes — soil above 18°C ideally. Zone 5 gardeners should wait until May 20+ and consider using black plastic mulch to boost soil temperature.

Basil — Frost kills basil instantly. Don't transplant until night temperatures are reliably above 10°C. Mid-May at the earliest for zone 6; late May for zone 5.

Direct Sow Warm-Season Crops

Beans — Direct sow when soil is above 15°C (beans rot in cold soil). Bush beans in zone 6 can go in May 10+; zone 5 gardeners wait until May 15–20. Sow 3–4 cm deep, 8 cm apart in rows 40 cm apart.

Summer Squash & Zucchini — Sow 2–3 seeds per hill, 90 cm apart, after last frost. Thin to 1 strong plant per hill. They grow fast — one or two plants are usually enough for a family.

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Late May (May 20–31): Full Garden in Motion

By late May across most of zones 5–6, all frost risk has passed and soil is warm. This is planting season in full swing.

Cucumbers — Direct sow or transplant after last frost. Cucumbers hate cold soil — wait until late May in zone 5. Sow 2–3 seeds per hill, 90–120 cm apart.

Corn — Needs a block of at least 4 rows for pollination. Sow late May when soil is above 15°C. Not practical in small gardens but a zone 6 staple.

Winter Squash & Pumpkins — These need the full season to mature. Sow late May in zone 6; very early June in zone 5 to ensure enough days before frost.

Sunflowers — Direct sow late May. They grow fast and tolerate light drought once established.

Keep Succession Sowing

Lettuce, radishes, beans, and salad greens should be re-sown every 10–14 days through May and into June for continuous harvests. Don't plant everything at once.

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May Indoor Starts: What to Start for Summer & Fall

While your outdoor garden gets busy, start these indoors for later transplanting:

• Late-season brassicas (broccoli, cabbage for fall harvest) — start indoors mid-May for August transplanting
• Celery — slow to germinate, start mid-May for July transplanting
• Leeks — start late May for fall harvest

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May Planting Checklist

All zones 5–6 (May 1–15):

• Peas (direct sow — last chance)
• Lettuce & salad greens (succession sow)
• Spinach, kale, chard
• Radishes, beets
• Carrots (when soil above 7°C)

Zone 6 (May 1–10) / Zone 5 (May 15–20 after last frost):

• Tomato transplants outdoors
• Broccoli, cabbage, cauliflower transplants
• Onion sets and transplants
• Bush beans (direct sow)
• Zucchini & summer squash (direct sow)

Late May (May 20–31):

• Cucumbers
• Peppers (zone 6) or wait until June (zone 5)
• Winter squash & pumpkins
• Basil (after nights reliably above 10°C)
• Continue succession sowing lettuce, beans, radishes

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Plan Your Full May Garden

Knowing what to plant is the starting point — timing it right for your specific zone, location, and last frost date is what separates a good harvest from a great one.

MyGardenPlanner.ca builds a personalized planting calendar for your garden based on your zone and location. It calculates exact seed start, transplant, and harvest windows — so you always know what to do next.

Get your free May planting calendar at mygardenplanner.ca