Every Ontario garden starts with two questions: when does spring really arrive, and when will fall finally shut us down? These frost dates—different in Toronto than in Sudbury, different again along the Niagara lakeshore—are the foundation of your garden calendar. Once you know your window, you can match crops to it, choose varieties with confidence, and spread out the work so you’re not planting everything on one frantic May weekend.
Ontario’s Garden Zones and Frost Dates
Here’s a broad look at growing zones and frost windows across Ontario. Use this as a guidepost, then fine-tune with your own local conditions.
| Region / Cities & Towns | Zone | Last Frost | First Frost |
|---|---|---|---|
| Windsor, Leamington, Chatham-Kent | 6–7 | Apr 25–May 10 | Oct 15–25 |
| London, St. Thomas, Sarnia | 6 | May 1–15 | Oct 10–20 |
| Hamilton, St. Catharines, Niagara | 6–7 | May 5–15 | Oct 15–25 |
| Toronto, Mississauga, Brampton | 6–7 | May 10–15 | Oct 10–20 |
| Barrie, Orillia, Collingwood | 5 | May 15–25 | Oct 1–10 |
| Kingston, Belleville, Napanee | 5–6 | May 10–20 | Oct 5–15 |
| Ottawa, Kanata, Orleans | 4–5 | May 15–25 | Sep 30–Oct 10 |
| Sudbury, North Bay, Espanola | 3–4 | May 25–Jun 1 | Sep 15–25 |
| Thunder Bay, Kenora, Timmins | 2–3 | Jun 1–10 | Sep 10–20 |
March and April: Seeds Indoors, Beds Outdoors
Late winter is seed-starting season. In Toronto or Hamilton, you might start onions and peppers as early as March. Tomatoes follow in early April—don’t rush them, they grow fast once they sprout.
If you’re still choosing varieties, we have a wide selection of tomatoes—from the quick and reliable Early Girl to golden, low-acid Carolina Gold and even tiny, super-sweet Candyland Red currants. Different varieties fit different zones and garden spaces, but all are selected for flavor and reliability.
Meanwhile, as soon as your soil can be worked—usually April in London or Niagara—you can sow peas, spinach, or radish directly outside.
May: The Move Outdoors
This is the gentlest, most important step: hardening off your seedlings. Give them a week to adjust, a few hours outdoors at a time, until they’re ready for full days and nights.
When the soil has warmed, it’s time for corn and beans. Corn loves heat, so in Windsor and Chatham you can sow by early May, but in Ottawa or Barrie it’s safer to wait until late May. If you want truly sweet, hold-the-flavor corn, try the Early Xtra Sweet SH2—perfect for eating fresh or freezing for later. Our full corn collection offers both early and late varieties so you can stagger the harvest.
Beans are forgiving and productive. For a quick win, go with a bush type like Bean Strike. If you have a trellis or fence, pole beans like the elegant Emerite French filet or the classic Ken Blue heirloom give long harvests and keep the garden vertical. Browse all our bean varieties here.
June and July: Abundance Begins
By June, most of Ontario is in full planting mode. In Niagara, you may already be picking early lettuce. Greens thrive with succession planting—sow a new patch every two weeks. Our Butterhead Mirlo is soft and creamy, Escarole Natacha stands up to pests, and Valley Heart Romaine keeps crisp texture even in warm spells.
Stake your tomatoes, mulch the beds, and water deeply once or twice a week. In Kitchener or Kingston, this is the moment to sow a second row of beans or a second block of corn for staggered harvests.
August and September: Plant for Fall
Don’t stop sowing in midsummer. Carrots, beets, and fall lettuces thrive in the cooler nights of August in Ottawa or Barrie. Cover them with a light row cover to extend harvests into October. Our carrot collection includes both early and storage types, so you can enjoy fresh crunch now and stash roots for winter meals.
This is also a good time to tuck in flowers. A strip of blooms from our flower collection draws pollinators, which means better yields for cucumbers, squash, and pumpkins.
October: The Gentle Close
In northern zones, frost comes quickly. Pick pumpkins before a hard frost and cure squash indoors. In southern zones, you might still be picking beans into mid-October. Garlic goes in last: plant cloves, mulch thick, and let them sleep until spring.
Our onion seeds and garlic sets (seasonally available) set you up for a harvest that keeps through winter—part of the rhythm of an Ontario garden.
Bringing It Together
Planning a 2026 Ontario garden isn’t about perfection. It’s about pacing: starting seedlings when the days are still cold, moving them out carefully in May, sowing successions in June and July, and remembering that August is a planting month, not just a harvesting one. With the right seeds for your zone, you can enjoy steady harvests from May peas to October garlic.
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