What to Plant in May in Canada (Zone 5, 6 & Beyond)

May is the month Canadian gardeners have been waiting for all winter. After months of seed starting, soil prep, and watching the forecast obsessively, the garden finally opens up. Last frost dates pass across most of the country between May 10 and May 25, and the planting window for warm-season crops — tomatoes, peppers, cucumbers, squash — arrives all at once. Whether you're in zone 5 Ottawa or zone 6 Toronto, May demands a plan. Here's exactly what to plant this month, when to plant it, and what to avoid.

May Planting at a Glance

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What to Transplant Outdoors in May

The big transplant push happens in May, but timing depends entirely on your last frost date. Putting tomatoes in the ground before that date — even in a warm spell — is a gamble you'll likely lose.

Zone 6 (Toronto, Hamilton, Vancouver): Last frost typically falls May 10–15. Once you've had a week of overnight lows above 5°C and the forecast looks clear, you're safe to transplant tomatoes, peppers, and eggplant. Early May works for cold-tolerant crops like brassicas and peas.

Zone 5 (Ottawa, Kingston, most of Ontario outside the GTA): Last frost is May 17–20. Hold warm-season transplants until the third week of May. Don't let a warm stretch in early May fool you — a late frost after May 15 is still possible.

Zone 4/5 (Edmonton, Saskatoon, Calgary): Last frost runs May 20–25. Calgary in particular can see frost well into late May. Wait for the long weekend as a rule of thumb, and keep row cover on hand.

Hardening Off — Don't Skip This

Seedlings started indoors need 7–10 days to adjust before they go in the ground. Start by setting them outside in a sheltered spot for a couple of hours, then gradually increase their outdoor time over the week. Skip this step and even a healthy transplant will sulk, stall, or sunscald. The last two days before planting, leave them out overnight (as long as no frost is forecast).

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What to Direct Seed in May

Once soil temperatures climb above 15°C, it's time to direct sow the warm-season crops that don't like root disturbance.

Beans are the easiest May sow. Bush beans take about 55–60 days from seed to harvest, so a late May sowing gives you beans by late July. Sow every two weeks for a continuous harvest. Soil temp needs to be at least 15°C — cold soil causes beans to rot rather than germinate.

Corn needs both warm soil (15°C minimum, 18°C ideal) and a block planting pattern for proper pollination. Sow in short rows side by side rather than one long row. Plant after last frost, and succession sow two weeks later for an extended harvest window.

Squash and cucumbers can be direct seeded mid-to-late May across most of zones 5 and 6. Both germinate quickly in warm soil and establish faster than transplants in some cases. If you started seeds indoors in early May, transplant carefully — cucumbers especially hate having their roots disturbed.

Carrots and beets can go in from early May onward — both tolerate a light frost and prefer cooler soil for germination. Sow carrots every two to three weeks through June for a succession harvest. Beets are versatile: harvest young for greens or let them size up for roots.

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Cool-Season Succession: Last Call

May is your last reasonable window for several cool-season crops before summer heat shuts them down.

Peas — Sow a final round in early May. They'll struggle to set pods if temperatures regularly hit 25°C+, so get them in the ground now. Zone 6 gardeners in warm microclimates may want to skip this if a hot May is expected.

Spinach and lettuce — Both bolt (go to seed) when days get long and hot. An early May sowing will give you a harvest in June before the heat arrives. Choose bolt-resistant varieties and consider a shaded spot to extend your window.

A note on succession planting: Rather than planting everything at once, staggering your lettuce, beet, and carrot sows every two to three weeks keeps harvests coming rather than arriving all at once. See our succession planting guide for a full framework.

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Last Frost Dates by Province

Getting your transplant timing right means knowing your local last frost date, not just your zone.

For exact dates by postal code, use the MyGardenPlanner.ca planting date calculator. See also our full Ontario planting dates reference.

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What to Avoid in May

Transplanting tomatoes before your last frost date. It's the most common May mistake. A single overnight frost at -2°C will blacken your transplants overnight. The excitement of a warm week in early May is a trap — check the 14-day forecast and know your zone's average last frost before anything goes in.

Planting peppers in cold soil. Even after frost danger has passed, peppers stall in soil below 15°C. If the ground feels cold, wait another week. Peppers planted in warm soil will catch up to — and pass — peppers planted two weeks earlier in cold soil.

Skipping hardening off. Covered above, but worth repeating. Transplant shock from skipping this step sets plants back by two to three weeks.

Sowing cool-season crops too late. Kale and broccoli transplants going in after May 20 in zone 6 will head straight into heat stress. If you've missed the window, wait and plan a fall sowing instead.

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Plan Your May Garden with MyGardenPlanner.ca

The dates above are zone averages — your specific microclimate, soil type, and local frost history matter too. For personalized planting dates based on your exact location, use the free planting date calculator at MyGardenPlanner.ca. Enter your postal code and get crop-specific transplant and direct seeding dates for your zone.

Also worth bookmarking: our seed starting schedule guide walks through the full indoor-to-outdoor timeline for every major crop, so next February you'll be ready for May well in advance.