Best Seeds to Plant in May in Canada: 7 Warm-Season Staples

By May, gardens across Canada are finally waking up in earnest. As soil temperatures rise and the risk of frost begins to retreat, we move away from the hardy greens of April and into the heavy hitters of the summer harvest.

While April is about resilience, May is about growth. This is the month we transition to crops that crave the sun and require "toasty" soil to thrive.

🌱 Read More | When to Direct Sow Seeds in Canada: The Ultimate Timing Guide

Why May is the Sweet Spot for Heat-Lovers

Many of our favorite summer vegetables are sensitive; planting them into cold, damp soil is a recipe for rot. Waiting until May ensures your seeds hit the ground running.

Minimum Soil Temperatures for Success:

• Beans: 15°C

• Corn: 16–18°C

• Cucumbers & Squash: 18°C+

Pro Tip: If you’re in a colder zone (3-5), use black plastic or a row cover to pre-warm your soil for a week before planting these varieties.

🌱 Read More | Soil Temperature Chart for Canadian Growers
🌱 Read More | How to Prepare Garden Soil for Planting

1. Beans (Bush and Pole)

Beans are the quintessential "easy win" for May. They germinate rapidly once the soil hits 15°C and offer a high yield for very little effort.

• How to Plant: Direct sow seeds about 3 cm deep.

• Caribou Choice: Plant bush beans for a quick, all-at-once harvest, or pole beans on a trellis to save garden space.

2. Sweet Corn

Nothing says summer like Canadian corn. Because corn is wind-pollinated, it has a specific planting "rule" to ensure full ears.

• How to Plant: Instead of one long, thin row, plant your corn in blocks (at least 4x4 rows). This ensures the wind can easily move pollen from the tassels to the silks.

3. Summer & Winter Squash

From prolific zucchinis to hearty butternuts, squash plants are the heavy lifters of the May garden.

• How to Plant: These are "space hogs." Give them plenty of room to roam, or choose "bush" varieties if you are working with smaller raised beds.

4. Basil

The king of summer herbs! Basil is notoriously dramatic about the cold. If there is even a hint of a late-May frost, keep these covered.

• How to Plant: Sow directly in the sunniest spot you have. Basil loves "wet feet" and "hot heads," so water the soil deeply while letting the leaves soak up the sun.

5. Cucumbers

Cucumbers are fast growers but very frost-sensitive. Wait until your local "frost-free date" has safely passed and the soil is a warm 18°C.

• How to Plant: Plant in "hills" (small mounds of soil) or along a sturdy trellis to keep the fruit off the ground and reduce disease.

6. Pumpkins

If you want a homegrown Jack-o'-lantern by October, May is your window. Like squash, pumpkins love rich soil and plenty of sun.

• How to Plant: Plant 2–3 seeds per mound. Once they are established, keep the strongest seedling to give it all the nutrients.

7. Sunflowers

For a touch of height and pollinator-friendly beauty, sunflowers are unbeatable. They are tough, fast-growing, and a great project for kids.

• How to Plant: Sow seeds 2–3 cm deep in a spot that receives at least 8 hours of direct light.

Quick Tips for May Success

• Check the Forecast: A "late-May surprise" frost is common in Canada. Keep your frost blankets handy just in case.

• Moisture is Key: Warm May sun can dry out the top inch of soil quickly. Ensure your newly sown seeds don't dry out during the germination phase.

• Succession Plant: For beans and basil, plant a new batch every two weeks to keep the harvest coming until September.

Seeds to Grab for May Planting

• 🌱 Beans – Fast-growing and productive

• 🌱 Corn – The block-planting classic

• 🌱 Cucumbers – Vertical or ground-creeping varieties

• 🌱 Squash – Zucchinis and more

Pole Bean 'Kentucky Wonder'	Bush Bean 'Blue Lake'	Corn 'Peaches n Cream'
Cucumber 'Marketmore'	Zucchini 'Black Beauty'	Butternut Squash

Final Thoughts
May is the bridge to the summer abundance we all work so hard for. By timing your planting with the rising soil temperatures, you’re setting your Caribou Seed Co. garden up for its most productive season yet.

🌱 Read More |  Best Seeds to Plant in April in Canada