Should I plant onion sets, transplants, or seed?

Each has tradeoffs. Sets (small dormant bulbs) are easiest — direct plant in spring, no indoor starting required, ready in 65–90 days. But variety selection is limited (mostly Stuttgart and a few yellows) and they're prone to bolting. Transplants from a nursery cost more but give wider variety choice and avoid bolting issues. Seed starting indoors gives access to every variety and the largest bulbs, but requires 12 weeks of indoor space and grow lights. For most Canadian gardens: nursery transplants in early spring give the best variety + ease balance.

When can I direct-seed onions outdoors in Canada?

Generally not recommended — Canada's growing season is too short. From direct seed, onions need 100–130 days to bulb, which means seed sown in late April (when soil reaches 4°C) won't be ready until August or September. Compare this to indoor-started seedlings transplanted in early May, which bulb by late July. Coastal BC is the exception — Vancouver and Victoria can direct-seed in February or early March and harvest by late summer. For everywhere else in Canada, start indoors or buy transplants.

What are the best onion varieties for Canada?

Long-day yellow storage: Cortland (105 days, the standard Canadian storage onion — keeps 8 months), Patterson (104 days, exceptional storage and flavour), Walla Walla (100 days, sweet, doesn't store as long but excellent fresh). Long-day red: Redwing (110 days, classic Canadian red storage onion), Red Wethersfield (heirloom). Long-day white: Sterling (107 days, mild flavour, popular in the Maritimes). Sets: Stuttgart Yellow is the most reliable — widely available at every Canadian garden centre in early spring.

When are onions ready to harvest in Canada?

When 50%+ of the tops have fallen over naturally — typically late July to September depending on region and start method. Indoor-started Cortland in Toronto: late August. Sets-grown onions in Ottawa: late July to mid-August. Coastal BC fall harvest: September. Don't bend tops over manually — this causes neck rot in storage. Pull when tops have flopped, cure in a warm dry shaded area for 2–3 weeks until necks are fully dry, then trim and store in a cool dry place. Properly cured Cortland keeps until April.

Why didn't my onions form bulbs?

Almost always wrong day-length variety — short-day onions planted in Canada produce leaves but no bulb. Buy long-day or intermediate-day varieties only. Second cause: planting too late. Onions need to develop adequate leaf mass before the day-length trigger hits in June — late-planted seedlings don't have enough leaves to support bulb formation. Third cause: excess nitrogen during bulbing — high-nitrogen fertilising in June and July produces leafy growth instead of bulbs. Stop nitrogen at the first signs of bulbing (mid-June).

Can I overwinter onions in Canada?

Coastal BC yes, rest of Canada largely no. Vancouver and Victoria can plant onion seed in late August or sets in October for an overwintering crop that bulbs the following June — earlier than spring-planted onions. Choose overwintering varieties (Walla Walla overwintering, Senshyu Yellow). Mulch heavily after the ground freezes lightly. For Toronto and east, hardy bunching/scallion types can overwinter under heavy mulch (Egyptian walking onions, perennial bunching), but bulb onions don't reliably survive.

CANADA PLANTING GUIDE

When to Plant Onions in Canada — Dates by Region

Q: When should I plant onions in Canada?

From seed: start indoors 10–12 weeks before last frost. Coastal BC: mid-December. Toronto: mid-January. Ottawa/Montreal: late January. Prairies (Calgary/Edmonton): early February. Halifax: mid-January. Transplant outdoors 2–4 weeks before last frost — onions tolerate light frost. From sets (small bulbs): plant directly outdoors 2–4 weeks before last frost. From nursery transplants: same timing as sets. Onions take 100–130 days from seed to bulb, which is why indoor starting is essential for most of Canada.

Q: Why do I need long-day onion varieties in Canada?

Onion bulb formation is triggered by day length, not heat. Long-day varieties bulb when daylight reaches 14–16 hours; short-day varieties bulb at 10–12 hours; intermediate at 12–14 hours. All of Canada is north of 45°N latitude, where summer day length exceeds 14 hours — only long-day varieties form proper bulbs here. Short-day varieties (sold for the southern US) won't bulb in Canada — they grow leafy and produce no harvest. Always check seed packets for 'long-day' designation.

Indoor-start dates by region (BC, Ontario, Quebec, Prairies, Maritimes), why Canada needs long-day varieties, the differences between sets, transplants, and seed, and the storage onion varieties that keep until April.

Onions are a long-game crop in Canada — 100 to 130 days from seed to bulb means most gardeners need to start indoors in January to harvest by August. The catch most beginners miss: onions form bulbs based on day length, not heat. Canada's high latitude means we need long-day varieties — short-day onions (sold for the southern US) grow leafy and never bulb here.

For most Canadian gardeners the easiest path is buying nursery transplants in early spring — they give wider variety choice than sets and avoid the 12-week indoor seed-starting commitment. From-seed indoor starting is rewarding for serious gardeners who want specific storage varieties (Cortland, Patterson, Redwing) that aren't available as sets.

Onions in Canada at a glance: Use long-day varieties only. From seed: start indoors 10–12 weeks before last frost. Toronto: mid-January. Ottawa/Montreal: late January. Prairies: early February. Coastal BC: mid-December. Transplant outdoors 2–4 weeks before last frost. From sets/transplants: plant directly outdoors at the same window.

Onion Planting Dates Across Canada — 2026

Indoor seed starting counts back 10–12 weeks from the safe transplant date (2–4 weeks before last frost). Sets and nursery transplants skip the indoor phase — plant directly at the transplant date.

Region (City)	Zone	Indoor Seed Start	Transplant / Set Date	Harvest
Vancouver Island (Victoria)	8b	Mid-Dec	Late Feb	Aug
Coastal BC (Vancouver)	8a	Late Dec	Early Mar	Aug
SW Ontario (Windsor)	7a	Early Jan	Late Mar–Early Apr	Late Jul–Aug
Southern Ontario (Toronto)	6b	Mid-Jan	Early–Mid Apr	Late Aug
BC Interior (Kelowna)	6b	Mid-Jan	Mid-Apr	Aug
Maritimes (Halifax)	6a	Mid-Jan	Mid-Apr	Late Aug
Eastern Ontario (Ottawa)	5a	Late Jan	Mid-Late Apr	Late Aug–Sep
Quebec (Montreal)	5b	Late Jan	Mid-Late Apr	Late Aug–Sep
Prairies (Edmonton)	4a	Early Feb	Late Apr–Early May	Sep
Prairies (Calgary/Winnipeg)	3a–3b	Early Feb	Early May	Sep

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The Universal Rules for Onions in Canada

Long-day varieties only — non-negotiable

All of Canada is north of 45°N latitude where summer day length exceeds 14 hours. Only long-day onion varieties bulb at this day length. Short-day varieties (sold for the southern US — Texas, Florida, southern California) grow leafy stalks and never form bulbs in Canada. Always check seed packets and transplant labels for "long-day" or "northern" designation. Intermediate-day varieties also work in Canada but are less reliable than dedicated long-day cultivars.

Maximize leaf mass before bulbing

Bulb size is determined by leaf size at the moment day length triggers bulbing (around June 21 in Canada). Each leaf produces one ring of the bulb — more leaves at trigger time means more rings and a larger bulb. This is why early planting matters: indoor-started onions transplanted in early April have 8 weeks of leaf development before the bulbing trigger. Sets planted late or seedlings transplanted in May have only a few weeks of leaf growth and produce small bulbs as a result.

Stop nitrogen at the first bulbing signs

Onions need consistent nitrogen during the leaf-development phase (April–May) but excess nitrogen during bulbing (mid-June onward) produces lush leaves at the expense of bulb development. Apply compost or balanced fertiliser in spring during transplanting and again 4 weeks later, then stop. When the first signs of bulbing appear (the bulb base begins to swell), no more nitrogen — only water. Mulch to prevent soil dry-out without adding nutrients.

Cure before storage — never skip this

After harvest, onions need 2–3 weeks of curing in a warm, dry, shaded, well-ventilated space before storage. The neck (where the leaves meet the bulb) must dry completely or onions rot in storage. Lay onions in a single layer on screens or hang in bunches. When the neck is fully dry and feels papery, trim leaves to 2–3 cm and remove dirty outer skins. Properly cured Cortland onions store for 8 months in a cool dry place; uncured onions rot within weeks.

Best Onion Varieties for Canadian Gardens

All long-day. Storage varieties (Cortland, Patterson, Redwing) keep through winter; sweet varieties (Walla Walla, Ailsa Craig) are eaten fresh and don't store. Sets are limited to a handful of varieties — for the full range, choose seed or nursery transplants.

Variety	Colour	Days	Storage	Why It Works in Canada
Cortland	Yellow	105	8+ months	Canada's standard storage onion. Reliable, prolific, exceptional storage life. The default choice for Ontario, Quebec, Maritimes.
Patterson	Yellow	104	9+ months	Best storage onion available — keeps until late spring. Slightly sweeter flavour than Cortland. Premium choice for serious cooks.
Walla Walla	Yellow	100	2–3 months	Famously sweet — eat fresh. Doesn't store long but unbeatable on burgers and salads. Coastal BC and Southern Ontario.
Redwing	Red	110	7+ months	Classic Canadian red storage onion. Vivid colour, firm texture, stores nearly as well as Cortland. The default red.
Sterling	White	107	5–6 months	Mild flavour, popular in the Maritimes. White onions don't store as long as yellows but cook beautifully.
Stuttgart Yellow	Yellow (sets)	85 (from sets)	4–5 months	The default set onion at every Canadian garden centre. Easy and reliable, but smaller bulbs than seed-grown varieties.

Common Onion Problems Across Canada

Onions don't form bulbs (just leaves)

Almost always wrong day-length variety — short-day onions planted in Canada produce only leaves. Replace with long-day or intermediate-day varieties. Other causes: planted too late (insufficient leaf mass before June 21), excess nitrogen during bulbing (high-nitrogen fertiliser in summer), or transplants that were too small at planting (less than pencil-diameter neck).

Bolting (flower stalk in summer)

Common with sets — onion sets that are too large (more than 1.5 cm diameter) often bolt because the bulb has already triggered reproductive growth. Choose smaller sets (under 1.5 cm) or buy nursery transplants instead. Cold-stress (sets exposed to prolonged cold below 5°C) also triggers bolting. Once a plant bolts, the bulb is small and won't store — harvest immediately and use fresh.

Bulbs rotting in storage (neck rot)

Inadequate curing. The neck must dry completely before storage — 2–3 weeks of warm dry curing. Don't bend tops over manually before harvest (this damages the neck and creates an entry point for rot). Don't wash bulbs after harvest. Don't store in plastic — use mesh bags, slatted crates, or hanging braids. Proper cool dry storage (2–10°C, low humidity) is essential.

Onion maggots

Small white maggots tunnel into onion bulbs, causing yellowing leaves and rot. Most damaging in early-season transplants. Floating row cover from transplant through mid-June prevents adult flies from laying eggs at the base of plants. Don't compost cull onions in the garden — they harbour overwintering pupae. Crop rotation (3+ years between onion crops in the same bed) breaks the lifecycle.

Frequently Asked Questions

When should I plant onions in Canada?

From seed: indoors 10–12 weeks before last frost. Toronto: mid-January. Ottawa/Montreal: late January. Prairies: early February. Coastal BC: mid-December. Transplant outdoors 2–4 weeks before last frost. Sets and nursery transplants: plant directly outdoors at the transplant date.

Sets, transplants, or seed?

Sets are easiest but limited to a few varieties (mostly Stuttgart). Nursery transplants give wider variety choice without indoor seeding — best for most gardeners. Seed gives every variety and the largest bulbs but requires 12 weeks of indoor space and grow lights. For storage onions like Cortland and Patterson, you'll need seed or specific nursery transplants — sets aren't usually available in those varieties.

Why do I need long-day varieties?

Onion bulbing is triggered by day length. All of Canada exceeds 14 hours of summer daylight, so we need long-day varieties (which bulb at 14–16 hours). Short-day varieties (10–12 hour bulbing) sold for the southern US won't bulb here — they grow leaves and stop. Always verify variety designation before buying.

When are onions ready to harvest?

When 50%+ of tops have fallen over naturally. Toronto: late August. Ottawa/Montreal: late August to September. Prairies: September. Don't bend tops manually — this causes neck rot. Cure for 2–3 weeks in warm dry shade before storing.

Can I direct-seed onions outdoors?

Generally not — Canada's growing season is too short for from-seed direct-sown onions. Coastal BC is the exception: Vancouver and Victoria can direct-seed in February for a late-summer harvest. Everywhere else, start indoors or buy transplants.

What's the best storage onion for Canada?

Cortland (the standard, 8+ months) and Patterson (best, 9+ months) for yellow. Redwing for red. Both need from-seed indoor starting or specific nursery transplants — they aren't sold as sets. Properly cured, these store from August harvest until April.