When to Plant Tomatoes in Ontario — City Guide
Exact indoor start dates and outdoor transplant dates for every major Ontario city — plus variety recommendations and common timing mistakes.
When to plant tomatoes in Ontario depends entirely on your city. Windsor and Toronto gardeners can transplant outdoors in late April — a full month before Ottawa and Kingston gardeners can safely do the same. Ontario spans three hardiness zones and nearly 1,400 km from Windsor to the Manitoba border, which means there's no single answer to this question.
This guide gives you exact start and transplant dates for every major Ontario city, the best tomato varieties for each zone, and how Ontario's timing and yields compare to BC and Quebec.
Ontario tomato planting at a glance: Start seeds indoors 6–8 weeks before last frost. Transplant outdoors 1–2 weeks after last frost once nights are consistently above 10°C. Toronto and Windsor: transplant early May. Ottawa and Kingston: transplant late May. Always harden off for 7–10 days before moving transplants outside.
When should you plant tomatoes where you garden?
Get your city's frost dates, indoor seed-starting dates, and this week's planting jobs — three free tools.
Outside Ontario? See the Canada-wide tomato planting guide for dates in BC, Quebec, the Prairies, and the Maritimes.
Ontario Tomato Planting Dates by City — 2026
All transplant dates assume a 1–2 week safety buffer after average last frost. Start-indoors dates are 6–8 weeks before transplant.
| City | Zone | Last Frost | Start Indoors | Safe Transplant | Max Variety Days |
|---|---|---|---|---|---|
| Windsor | 7a | Apr 20 | Mar 1–15 | May 1–5 | 85 days |
| Toronto | 6b | Apr 20 | Mar 1–15 | May 1–10 | 80 days |
| Hamilton | 6b/7a | Apr 25 | Mar 1–15 | May 5–10 | 80 days |
| London | 6a | Apr 30 | Mar 5–20 | May 10–15 | 78 days |
| Kingston | 5b | May 5 | Mar 15–30 | May 15–20 | 75 days |
| Ottawa | 5a | May 9 | Mar 24–Apr 9 | May 20–25 | 72 days |
Get Your Exact Tomato Start Dates
Enter your city and get a personalized seed starting calendar for tomatoes and 20+ other vegetables
🌱 Free Seed Starting CalculatorBest Tomato Varieties for Ontario
Variety selection matters as much as timing. Ontario's range of zones means the right variety for Windsor is different from the right variety for Ottawa. Days to maturity is the key spec — count from transplant date to first fall frost to see how much margin you have.
🍅 Cherry & Small Tomatoes (50–65 days) — Best for all Ontario
🍅 Mid-Size & Slicing (62–75 days) — Southern & Central Ontario
🍅 Heirloom & Large (75–85 days) — Toronto, Hamilton, Windsor only
These varieties need the longer seasons of southern Ontario cities. Ottawa and Kingston gardeners should avoid 80+ day varieties — the margin is too tight. Toronto has room; Windsor has the most flexibility of any Ontario city.
Ontario Tomato Planting Dates by Region
Tomatoes need warm soil (16°C minimum, 18°C ideal) and zero risk of frost — Ontario's last frost dates vary by 4–5 weeks across the province. Indoor sowing is 6–8 weeks before transplant; set-out is the line below.
| Ontario region | Zone | Start indoors | Transplant out | Cities |
|---|---|---|---|---|
| Niagara / Carolinian | 7a | March 15–25 | May 15–20 | St. Catharines, Niagara-on-the-Lake, Pelee Island |
| Southwestern ON | 6b–7a | March 20–30 | May 18–25 | Windsor, London, Sarnia, Chatham-Kent |
| GTA / Golden Horseshoe | 6a–6b | March 25–April 5 | May 24–June 1 | Toronto, Mississauga, Hamilton, Oakville |
| Central ON / Lake Simcoe | 5a–5b | April 1–10 | May 28–June 5 | Barrie, Orillia, Peterborough, Kawartha Lakes |
| Eastern ON / Ottawa Valley | 5a–5b | March 28–April 8 | May 25–June 3 | Ottawa, Kingston, Cornwall, Pembroke |
| Northern ON | 3b–4b | April 10–20 | June 5–15 | Sudbury, North Bay, Thunder Bay, Timmins, Sault Ste. Marie |
Ontario Tomato Pest & Problem Watchlist
Tomatoes are Ontario's most-grown vegetable and they attract the most pest and disease problems. Scout weekly; many issues compound if left unchecked into August.
Tomato hornworm
Fat green caterpillar with a red horn — can defoliate a plant overnight in late July–August. Look for black droppings and stripped stems. Control: hand-pick at dusk with a flashlight (UV light makes them glow); spray Bt; leave caterpillars covered in white rice-like cocoons alone — those are parasitized and will produce beneficial wasps.
Early blight & late blight
Early blight: yellow lower leaves with brown bullseye spots, working up the plant. Late blight: rapid greasy lesions on leaves and fruit — kills plants in 7–10 days, devastating in wet Augusts. Control: mulch heavily to prevent soil splash; prune lower leaves; copper spray weekly from mid-July; remove and bag infected leaves immediately; 3-year rotation away from tomatoes and potatoes.
Blossom-end rot
Black sunken patches on the bottom of ripening fruit — caused by inconsistent watering blocking calcium uptake, not a calcium deficiency. Control: deep weekly watering, never let beds dry to wilt point; thick mulch; avoid high-nitrogen fertiliser; the first cluster is often affected, later fruit usually fine.
Cracking & splitting
Ripening fruit splits along the shoulders after a heavy rain following dry weather. Concentric cracks form rings; radial cracks split from the stem. Control: consistent watering; mulch to buffer rainfall swings; harvest ripening fruit before a forecast heavy rain; choose crack-resistant varieties (Mountain Magic, Juliet, Sun Gold).
Aphids & whitefly
Soft-bodied insects clustering on new growth or under leaves — they spread viruses and produce sticky honeydew that grows sooty mould. Control: blast off with a hose every few days; insecticidal soap; encourage ladybugs and lacewings by leaving a strip of dill/fennel/yarrow flowering; remove badly infested side shoots.
Common Ontario Tomato Timing Mistakes
Starting seeds too early
The most common mistake. Tomatoes started in late January or early February are 14–16 weeks old by transplant time — they're root-bound, leggy, and stressed. This causes delayed fruiting, not earlier harvests. Stick to 6–8 weeks before your transplant date. For Ottawa, that means starting no earlier than late March.
Transplanting on last frost date, not after it
Last frost dates are averages — there's roughly a 50% chance of frost after that date. For frost-sensitive tomatoes, add 1–2 weeks. Toronto's last frost is April 20 but experienced Toronto gardeners don't plant tomatoes outside until May 1–10. Ottawa's May 9 last frost means safe transplanting is May 20–25.
Skipping hardening off
Tomato seedlings grown indoors under lights aren't ready for direct sun, wind, and temperature swings. Skipping hardening off causes transplant shock — plants wilt, stop growing for 2–3 weeks, and may never fully recover. Spend 7–10 days gradually exposing seedlings to outdoor conditions before transplanting. Start with 1–2 hours of shade and work up to full sun over a week.
Choosing the wrong variety for your zone
An 85-day tomato planted in Ottawa on May 24 needs to reach maturity by October 12 — that's only 141 days, which sounds fine until you realize "days to maturity" counts from transplant, and the plant needs warm soil to set and ripen fruit. Ottawa gardeners consistently get better results from 65–72 day varieties than from pushing 80-day heirlooms. Save the big heirlooms for Toronto and Windsor.
How Ontario Compares — BC and Quebec
Ontario isn't the only province growing great tomatoes. Here's how the timing and yields compare across Canada's three main tomato-growing regions.
| City | Last Frost | Safe Transplant | July High | Best For |
|---|---|---|---|---|
| Vancouver, BC | Mar 15 | Late Apr | 22°C | Cherry & small varieties — cool summers slow ripening |
| Kelowna, BC | Apr 15 | Early May | 29°C | Best tomato climate in BC — hot, dry summer ideal |
| Toronto, ON | Apr 20 | May 1–10 | 27°C | Excellent — hot summers, long season, any variety to 80 days |
| Ottawa, ON | May 9 | May 20–25 | 26°C | Good — hot summers but shorter season, stick to 72 days |
| Montreal, QC | May 9 | May 20–25 | 27°C | Very similar to Ottawa but slightly hotter — 75 day varieties reliable |
| Windsor, ON | Apr 20 | May 1–5 | 28°C | Best inland tomato city in Canada — any variety to 85 days |
Why Vancouver tomatoes disappoint despite early starts
Vancouver gardeners can transplant tomatoes in late April — weeks before Ontario. But Vancouver's cool July temperatures (22°C average high) mean tomatoes take much longer to ripen than in Toronto or Montreal (26–27°C). A Sun Gold tomato transplanted May 1 in Vancouver and May 10 in Toronto will often be ready to harvest at the same time. Ontario's hot summers more than compensate for the later start date. Kelowna and the Okanagan are the exception — BC's interior heat rivals Ontario's best.
Frequently Asked Questions
When should I plant tomatoes in Ontario?
Transplant after your city's last frost date plus a 1–2 week buffer: Toronto and Windsor — May 1–10; Hamilton — May 5–10; London — May 10–15; Kingston — May 15–20; Ottawa — May 20–25. Start seeds indoors 6–8 weeks before those dates. Always harden off for 7–10 days first.
When do I start tomato seeds indoors in Ontario?
Toronto/Windsor/Hamilton: early to mid-March. London/Kingston: mid to late March. Ottawa: late March to early April. Do not start earlier — leggy, root-bound seedlings are worse than seedlings started at the right time.
Can I grow heirloom tomatoes in Ontario?
Yes — in Toronto, Hamilton, and Windsor. 80-day heirlooms like Brandywine and Cherokee Purple ripen comfortably in these cities. In Ottawa and Kingston, stick to varieties under 72–75 days — the season is too short for reliable heirloom production. The seed starting calculator will show exactly how many frost-free days you have from transplant to first fall frost.
When to plant tomatoes in Ontario vs BC?
Vancouver transplants go out in late April — 2–3 weeks before Toronto. But Ontario's hotter summers (26–27°C July highs vs Vancouver's 22°C) mean Ontario tomatoes often ripen at the same time despite the later start. Kelowna is the exception — BC's interior has both early starts and hot summers, making it one of Canada's best tomato regions alongside Windsor.
📖 Ontario City Planting Guides
Full planting calendars for every vegetable in your city.