When to Plant Spinach in Ontario — 2026 Guide
Spring and fall sowing dates for every major Ontario city — why spinach bolts in summer, the best bolt-resistant varieties, and how to get two full harvests per season.
When to plant spinach in Ontario is one of the earliest questions of the gardening year — spinach is a cool-season crop that goes in the ground weeks before last frost, as soon as soil is workable above 4°C. Toronto and Windsor gardeners can sow their first spinach in late March. Ottawa and Kingston start in early April. And unlike warm-season crops, spinach can actually be harmed by waiting too long — it bolts and turns bitter once Ontario's long summer days arrive in May.
This guide covers spring and fall sowing dates for every major Ontario city, why spinach bolts (and how to delay it), the best bolt-resistant varieties, and how to get a productive fall crop that's often sweeter than the spring harvest.
Ontario spinach at a glance: Spring sow 4–6 weeks before last frost — as soon as soil reaches 4°C. Toronto/Windsor: late March–early April. Ottawa/Kingston: early–mid April. Succession sow every 2 weeks until mid-May. Fall crop: sow 6–8 weeks before first frost — August. Spinach bolts in summer — switch to Swiss chard for the gap.
Ontario Spinach Planting Calendar — Spring 2026
Spring sowing starts when soil is workable — above 4°C. Spinach tolerates light frost and even snow on established plants. Last spring sowing is mid-May before heat and long days trigger bolting.
| City | Zone | First Spring Sowing | Last Spring Sowing | Spring Harvest |
|---|---|---|---|---|
| Windsor | 7a | Mar 20–Apr 1 | May 15 | May–Jun |
| Toronto | 6b | Mar 25–Apr 5 | May 15 | May–Jun |
| Hamilton | 6b/7a | Mar 25–Apr 5 | May 15 | May–Jun |
| London | 6a | Apr 1–10 | May 15 | May–Jun |
| Kingston | 5b | Apr 5–15 | May 15 | Late May–Jun |
| Ottawa | 5a | Apr 5–15 | May 15 | Late May–Jun |
Ontario Spinach Planting Calendar — Fall 2026
Fall spinach is sown in August — 6–8 weeks before first fall frost. As days shorten and temperatures cool, bolting slows and flavour improves. Fall spinach is often sweeter than spring spinach.
| City | First Fall Frost | Fall Sowing Window | Fall Harvest | Extend With Cover |
|---|---|---|---|---|
| Windsor | Oct 28 | Aug 15–Sep 1 | Oct–Nov | Into December |
| Toronto | Nov 1 | Aug 15–Sep 1 | Oct–Nov | Into December |
| Hamilton | Oct 28 | Aug 15–Sep 1 | Oct–Nov | Into November |
| London | Oct 20 | Aug 10–25 | Oct | Into November |
| Kingston | Oct 15 | Aug 5–20 | Sept–Oct | Into October |
| Ottawa | Oct 12 | Aug 5–20 | Sept–Oct | Into October |
Why Spinach Bolts in Ontario Summers
Bolting — when spinach sends up a flower stalk, leaves become small and bitter, and the plant stops producing — is the defining challenge of Ontario spinach growing. Understanding what triggers it lets you time your sowings to avoid it.
What causes bolting: Spinach bolts in response to long days combined with warmth — not heat alone. Once day length exceeds approximately 14 hours (which happens around May 20 in Ontario), spinach begins preparing to flower. Heat accelerates this, but even cool temperatures won't stop bolting once day length passes the trigger. This is why even well-watered, shaded spinach bolts in June in Ontario — day length is the cause, not neglect.
Spring strategy
Sow early (late March–April) so plants mature and you harvest heavily before May 20 long-day trigger. Choose bolt-resistant varieties. Succession sow every 2 weeks to extend season. Accept that June ends the spring crop.
Fall strategy
Sow in August when days are already shortening. As fall progresses, bolting trigger disappears entirely. Fall spinach grows slowly but steadily through September and October. Frost improves sweetness. Use row cover to extend into November.
Best Spinach Varieties for Ontario
Bolt resistance is the primary spec for spring sowings. Days to maturity matters for fall sowings — fast varieties ensure harvest before hard frost.
Most bolt-resistant hybrid available. Semi-savoy (slightly crinkled) leaves. Excellent for extending the spring season in Ontario. Works for fall as well.
Classic heirloom, slow to bolt for an open-pollinated variety. Heavily savoy (crinkled) leaves with rich flavour. Best all-round Ontario spinach for gardeners who prefer heirlooms.
Fast, smooth (flat) leaf. Widely available at Ontario garden centres. Very productive. Upright growth habit makes harvesting easier. Good for both spring and fall.
Very fast hybrid. Dark green, upright leaves. Excellent for fall sowing in Ottawa and Kingston where speed matters. Also good for spring baby leaf harvesting.
Fastest for baby leaf harvest. Sow thickly, harvest young at 5–8 cm. Succession sow every 2 weeks for continuous baby spinach. Excellent for containers and raised beds.
Heat-tolerant summer alternative. Not true spinach but similar flavour and use. Grows through Ontario's summer heat when regular spinach cannot. Direct sow after last frost.
Ontario Spinach Growing Tips
Succession sow every 2 weeks in spring
Each spinach sowing produces a harvest window of about 2–3 weeks before bolting. Sowing every 2 weeks from late March through mid-May gives a continuous spring harvest from May through early June. Sow small amounts frequently rather than one large sowing — a 30 cm row every 2 weeks is plenty for fresh eating for two people.
Harvest outer leaves continuously — don't cut the whole plant
Harvest spinach by picking the outer, larger leaves and leaving the inner growing point intact. The plant continues producing new leaves from the centre. This cut-and-come-again approach extends each plant's productive life by 2–3 weeks compared to harvesting the whole plant at once. Once the plant sends up a central flower stalk, harvest everything immediately — the leaves will become bitter within days.
Partial shade delays bolting in May
Planting spring spinach in a spot that gets afternoon shade — from a fence, taller plants, or shade cloth — reduces the heat stress that accelerates bolting. Shade doesn't stop bolting (day length is the primary trigger) but it delays it by 1–2 weeks by keeping plants cooler. In Ontario gardens, planting spinach on the east side of taller crops or structures so it gets morning sun and afternoon shade is a practical strategy for extending the spring harvest.
Use row cover to extend both ends of the season
A lightweight frost blanket (row cover) extends both the spring and fall spinach seasons in Ontario. In spring, use it over early March sowings to protect against hard frosts below -5°C — spinach tolerates light frost to about -2°C unprotected, to -8°C under cover. In fall, use it over August sowings to keep plants productive through October and even November in Toronto and Windsor. Row cover is the single most useful season extension tool for Ontario spinach growers.
Bridge the summer gap with Swiss chard and New Zealand spinach
When your spring spinach bolts in June, don't leave the bed empty — succession plant with Swiss chard (which doesn't bolt in heat and tastes similar) or New Zealand spinach (which produces abundantly through Ontario's hottest months). Both bridge the gap until your fall spinach is ready in September. This keeps the growing space productive year-round and means you're never without leaf greens through the Ontario season.
How Ontario Compares — BC and Quebec
Spinach is one of the few vegetables where coastal BC has a decisive advantage over Ontario — mild winters allow near year-round production.
| City | First Spring Sow | Fall Sow | Overwinter? | Notes |
|---|---|---|---|---|
| Victoria, BC | Feb–Mar | Aug–Oct | Yes — outdoors | Near year-round production possible |
| Vancouver, BC | Feb–Mar | Aug–Sep | Yes — with protection | Cold frame extends to Dec–Jan |
| Toronto, ON | Late Mar–Apr | Aug 15–Sep 1 | No | Two seasons: spring and fall |
| Ottawa, ON | Early–mid April | Aug 5–20 | No | Shorter fall window — sow early August |
| Montreal, QC | Early–mid April | Aug 5–20 | No | Same as Ottawa — nearly identical timing |
| Kelowna, BC | Late Mar–Apr | Aug–Sep | No | Similar to Toronto — two seasons |
Frequently Asked Questions
When should I plant spinach in Ontario?
Spring: 4–6 weeks before last frost when soil reaches 4°C. Toronto and Windsor: late March to early April. Ottawa and Kingston: early to mid-April. Fall: 6–8 weeks before first fall frost — August for all Ontario cities. Use the frost calculator for your city's exact frost dates.
Can I plant spinach in May in Ontario?
Yes, but expect it to bolt quickly. A mid-May sowing in Ontario will often bolt within 3–4 weeks as days lengthen past 14 hours and heat arrives. Use a bolt-resistant variety like Tyee and harvest young. By June, spinach is generally done for the season. The spring window for spinach in Ontario is March/April — May is pushing the limit.
What can I grow instead of spinach in summer?
Swiss chard is the best summer substitute — similar flavour and nutrition, thrives in Ontario's summer heat, and doesn't bolt. New Zealand spinach (not true spinach) produces abundantly through the summer and is used the same way. Malabar spinach is another heat-tolerant option. All three bridge the gap between your June spring spinach and your September fall spinach.
Does spinach survive frost in Ontario?
Yes — spinach tolerates light frost to about -2°C without protection, and to -8°C under row cover. Spring-sown seedlings can handle light snow. Established fall spinach plants survive Ontario's first fall frosts and often taste sweeter after cold exposure. The point where spinach needs protection or dies is a sustained hard freeze, not light frosts — making it one of the hardiest salad crops for Ontario.
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