Growing Onions in Canada — Long-Day Varieties, Sets vs Transplants & Storage
Why long-day varieties are the only ones that bulb in Canadian gardens, the three planting methods (sets, transplants, direct seed) and which to choose by region, curing for winter storage, and defending against onion maggot, neck rot, and downy mildew.
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Onions look easy and mostly are — but two upstream decisions determine whether you get a pantry full of storage onions or a tray of disappointing scallions: choosing a long-day variety, and picking the right planting method for your region. Get those right and a 4-foot row of transplants yields 100-150 onions that store 6-12 months at $0 a kilo.
What follows is onion growing for actual Canadian conditions: the long-day rule, sets vs transplants vs direct seed, planting and care, harvest signals, the 2-3 week cure, winter storage, and the 5 most common Canadian onion problems — led by onion maggot.
Growing onions in Canada at a glance: Plant long-day varieties only (Copra, Patterson, Walla Walla, Stuttgarter) — short-day Southern US varieties fail here. Use transplants for storage onions; sets for green onions only. Plant 2-4 weeks before last frost. Row-cover from day one to block onion maggot. Harvest when tops flop over (mid-August to early September). Cure 2-3 weeks dry, then store at 0-4°C, 60-70% humidity, dark for 6-12 months.
When should you plant onions where you garden?
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The Long-Day Rule — Why It Matters
Onions start forming bulbs when day length reaches a variety-specific threshold. Canada sits at 43°N to 70°N, so summer days are 14-16+ hours long — only long-day varieties bulb properly here.
| Type | Bulbing Trigger | Canada Verdict | Examples |
|---|---|---|---|
| Long-day | 14-16 hours daylight | YES — the only reliable choice | Copra, Patterson, Walla Walla, Stuttgarter, Cortland, Redwing |
| Day-neutral | 12-14 hours daylight | Marginal — works but smaller bulbs | Candy, Superstar |
| Short-day | 10-12 hours daylight | NO — will not bulb in Canada | Texas Grano, Vidalia, Bermuda |
⚠️ Why short-day onions fail in Canada. Short-day varieties trigger bulbing as soon as day length hits 10-12 hours — that happens in March in southern Canada, before any meaningful leaf growth. Every leaf that emerges before bulbing becomes one ring of the bulb. Short-day onions in Canada start bulbing with 2-3 leaves and produce scallion-sized bulbs or none at all. Always check the seed packet or catalogue label — American garden brands often stock all three types side-by-side. Canadian seed houses (Veseys, William Dam, West Coast Seeds) only stock long-day + day-neutral.
Sets vs Transplants vs Direct Seed
| Method | Best For | Cost (per row) | Pro | Con |
|---|---|---|---|---|
| Sets (small dry bulbs) | Green onions, smaller cooking onions, beginners | $5-8 | Easiest. Available everywhere March-April. Quick to plant. | Often unlabeled variety. Prone to bolting. Poor long-term storage. |
| Transplants (bundled seedlings) | Storage onions, large bulbs, Prairie + northern | $15-20 (60-75 plants) | Best yield + storage. Known variety. Storage-grade. | Pre-order from Veseys/Dixondale by January. Higher cost. |
| Direct seed | Coastal BC + southern Ontario (long springs) | $3-5 | Cheapest. Biggest variety choice. Best storage. | Needs warm early soil — not viable Prairies, northern Canada. |
| Indoor start from seed | All Canada, big budget gardens | $5-10 + lights | Big variety choice + healthy transplants. Cheap per plant. | 10 weeks indoor under lights at 18-20°C. Hardening required. |
Best Canadian Onion Varieties
| Variety | Type | Storage | Notes |
|---|---|---|---|
| Copra | Yellow storage | 8-12 months | The Canadian storage classic. Dense, pungent, reliable. |
| Patterson | Yellow storage | 8-12 months | Cornell-bred Copra replacement. Higher yield, same storage. |
| Walla Walla | Yellow sweet | 3-5 months | Large mild eating onion. Pacific Northwest heirloom. |
| Stuttgarter | Yellow storage | 6-8 months | Heirloom, flat shape. The standard 'set' variety in Canada. |
| Cortland | Yellow storage | 6-8 months | Early-maturing — ideal for short Prairie season. |
| Redwing | Red storage | 5-7 months | Best-storing red. Burgundy skin, white-pink flesh. |
| Red Wethersfield | Red slicing | 3-5 months | Heirloom flat red, slicing-style. Mild sweet. |
| Ailsa Craig | Yellow giant | 3-4 months | Heirloom — 700 g+ bulbs. Show onion. Eat fresh. |
| Cipollini | Specialty flat | 4-6 months | Small Italian flat onions. Roast whole. |
| Egyptian Walking | Perennial | N/A (in-ground) | Perennial scallions. Hardy to Zone 2. Plant once, harvest forever. |
Planting Window by Canadian Region
| Region / City | Zone | Sets/Transplants Out | Direct Seed | Harvest |
|---|---|---|---|---|
| Coastal BC (Victoria, Vancouver) | 8a-9a | Late March to mid-April | Mid March | Mid-July to late August |
| Southern Ontario (Toronto, Hamilton) | 6a-7a | Mid-April to early May | Early April | Late July to early Sep |
| Ottawa / Montreal | 5a-5b | Late April to mid-May | Mid April (light frost OK) | Early August to mid-Sep |
| Halifax / Maritimes / PEI | 5b-6a | Early to mid May | Late April | Mid-August to mid-Sep |
| Calgary / Edmonton | 3b-4a | Mid May (after hard frost) | Use transplants instead | Late August to early Sep |
| Winnipeg / Saskatoon / Regina | 3a-3b | Mid May | Use transplants instead | Late August to early Sep |
| St. John's NL | 5b-6a | Mid to late May | Use transplants instead | Late August to mid-Sep |
Planting and Care
- Bed prep: loose well-drained soil. Work in 5 cm of compost. Soil pH 6.0-6.8. See Composting in Canada.
- Spacing: transplants and sets 10-15 cm apart for storage bulbs (wider = bigger bulbs); 5 cm for green onions. Rows 30 cm apart.
- Planting depth: shallow! Plant transplants and sets so the top of the bulb sits at soil level — deeper and bulbs stay small. Direct seed 1 cm deep.
- Row cover immediately — from day one until early July. Blocks onion maggot adults (the #1 Canadian onion pest) and increases spring soil temperature.
- Water consistently: 2.5 cm/week, more in hot dry weather. Drip or soaker preferred. Stop watering when tops start to flop (2-3 weeks before harvest) — helps cure-readiness. See Watering in Canada.
- Feeding: light side-dress of balanced organic fertilizer at 6 weeks. Stop feeding by mid-summer — late nitrogen produces lush tops at the expense of bulb formation and storage life.
- Weed often, weed shallow — onions have shallow roots; deep cultivation damages them. Hand-pull within 5 cm of plants. Mulch lightly with straw after bed warms.
Sources: onion planting depth — common gardening practice; consistent with this site’s growing-onions guide.
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Onion Maggot — Canada's #1 Onion Pest
Delia antiqua — the onion root maggot — is the single biggest Canadian onion threat, especially in Ontario, Quebec, and the Maritimes. Three generations per summer can destroy a row. Defence is preventive only — once larvae are inside the bulb, nothing reaches them.
- Row cover from day of planting until early July — the most effective control. Adult flies cannot reach the plants to lay eggs.
- Crop rotation — never plant onions/garlic/leeks/shallots in the same bed two years running. Overwintering pupae emerge from previous Allium soil.
- Transplants beat sets and direct seed — healthier larger plants tolerate light damage better.
- Diatomaceous earth ringed around plants at planting deters egg-laying.
- Beneficial nematodes (Steinernema feltiae) applied to soil at planting in heavy-pressure areas.
- Avoid fresh composted manure near onions — the ammonia attracts adult flies.
- Onion + carrot interplant — the volatile oils confuse onion maggot and carrot rust fly. Less effective alone than row cover but stacks well.
Lightweight reusable row cover blocks onion maggot, leek moth, and cabbage root fly while letting in 85%+ light and rain. Cover from day of planting until early July, then remove.
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Harvest, Cure, Store
Harvest signal
Tops have yellowed and 50%+ of the tops have flopped at the neck. Do NOT bend tops over manually — the old "bend tops" advice is wrong. Bending interrupts the natural curing process and shortens storage. Let them fall on their own. Wait for a dry day; harvest before fall rains — wet bulbs at harvest is the #1 cause of neck rot in storage.
Cure 2-3 weeks
Lay or hang harvested onions in a single layer in a dry well-ventilated shaded area at 20-30°C, 60-70% humidity. A garage, covered porch, shed, or attic works. Direct sun cooks the bulbs; damp basements grow mold. Use a fan to improve airflow indoors. Done when: outer skin paper-dry and tight, neck dry and shrunken, tops fully brown halfway down.
Trim and store 6-12 months
After curing, cut tops 2-3 cm above the bulb. Store at 0-4°C, 60-70% humidity, complete darkness. Mesh bags, paper bags, braided strings, ventilated crates — never plastic. Unheated basement, root cellar, attached garage in mild winters, or insulated shed. Check monthly — remove any soft, sprouted, or moldy bulbs (one bad onion ruins the bag). DO NOT store with potatoes (release moisture). Garlic and winter squash store well alongside.
Cured onions keep for months only if air can reach every bulb — the reason mesh beats plastic, which traps the moisture that rots them. Hang a breathable mesh bag in a cold, dark, dry spot and the onions stay firm through winter; it also makes the monthly check easy (pull any soft one before it spoils the bag). This reusable 5-pack (4.4★, 1,890 reviews) works the same for garlic and cured squash.
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Where to Buy Canadian Onion Seed, Sets, and Transplants
- Veseys Seeds (Charlottetown, PEI) — sets, seed, and transplant bundles. Ships nationally. The standard.
- Dixondale Farms (Texas, ships to Canada) — the largest onion-transplant supplier in North America. Order by January for spring delivery.
- William Dam Seeds (Dundas, ON) — broad seed selection.
- West Coast Seeds (Delta, BC) — BC + Coastal varieties.
- Eagle Creek Farms (Bowden, AB) — Prairie-adapted varieties.
- Solana Seeds (Quebec) — specialty + heirloom.
5 Most Common Canadian Onion Problems
| Problem | Symptoms | Fix |
|---|---|---|
| Onion maggot | Wilting + yellowing leaves, roots eaten, white maggots in bulb | Row cover day 1 to July, rotate annually, transplants over sets, diatomaceous earth |
| Neck rot (Botrytis) | Soft watery rot at neck of stored bulbs, weeks after harvest | Harvest dry, cure 2-3 weeks until neck bone-dry, store at 60-70% humidity |
| Bolting (flower stalk, no bulb) | Flower stalk forms, plant stops bulbing | Use transplants over sets, snap stalk early, water consistently, eat bolted bulbs fresh — do not store |
| Downy mildew | Pale-yellow patches, grey fuzz on leaf underside | Spacing for airflow, water at soil level only, preventive copper spray in wet regions |
| Thrips | Silvery streaks on leaves, tiny tan insects | Morning overhead spray (raises humidity), insecticidal soap, predatory mites |
Related Canadian Guides
Plan your onion planting date
Find your last frost date and the 2-4 week window before it — that's your transplant date.
Open the Frost Calculator →Frequently Asked Questions
When should I plant onions in Canada?
Onions are one of the earliest things you can plant — they tolerate frost. **Sets and transplants**: 2-4 weeks before last frost. **Direct seed (early-only)**: 4-6 weeks before last frost, when soil is workable at 5°C+. **Indoor seed start**: 8-10 weeks before transplant date. By zone: **Coastal BC**: late March to mid-April. **Toronto/Hamilton**: mid-April to early May. **Ottawa/Montreal**: late April to mid-May. **Halifax/Maritimes**: early to mid-May. **Calgary/Edmonton/Winnipeg**: mid-May. The earlier the better — onions need maximum leaf growth before the long-day signal triggers bulbing in mid-June. Every leaf that emerges before bulbing equals one ring in the bulb — more pre-bulb leaves means a larger onion.
Why must I grow long-day onions in Canada?
Onions start forming bulbs when day length reaches a specific threshold — the long-day signal. Canada (43°N to 70°N) gets 14-16+ hours of summer daylight, so only long-day varieties (requiring 14-16 hours to trigger bulbing) form proper bulbs here. **Long-day (Canada, all)**: Walla Walla, Yellow Sweet Spanish, Stuttgarter, Copra, Patterson, Cortland, Frontier, Redwing, Red Wethersfield. **Day-neutral (Canada-marginal but workable)**: Candy, Superstar (form bulbs at 12-14 hours; smaller crop in Canada). **Short-day (DO NOT plant in Canada)**: Texas Grano, Vidalia, Bermuda — require only 10-12 hours, so they trigger bulbing at our late-winter day length, before any leaf growth has happened — result: scallion-sized 'bulbs' or none at all. Seed catalogue mistakes: avoid southern US seed varieties unless explicitly labelled long-day. Veseys, William Dam, West Coast Seeds — their Canadian catalogues only stock long-day + day-neutral.
Onion sets, transplants, or seed for Canadian gardens?
Three valid methods, different trade-offs. **Sets (small dry bulbs)** — easiest, fastest, most popular. Available at every garden centre in March-April. Plant 2 weeks before last frost. Risk: many varieties not labelled; sets often bolt (flower instead of forming bulbs) in cold springs. Good for: green onions/scallions, smaller cooking onions. Use within 4-5 months — do not store long-term. **Transplants (pencil-sized seedlings, bundles of 50-75)** — the storage-onion choice. Available from Veseys, Dixondale Farms (mail order to Canada), local nurseries. Plant 2-4 weeks before last frost. Best yield + best storage. Cost: $15-20 per bundle (60-75 plants). The Canadian commercial standard. **Direct seed** — cheapest, biggest variety choice, but only viable in Coastal BC + southern Ontario where soil warms early enough. Sow 4-6 weeks before last frost, 2 cm deep. **Indoor start from seed**: 8-10 weeks before transplant date in coir pots under lights at 18-20°C. Harden off 2 weeks before planting. Choose method: Prairies + most of Canada = transplants. Coastal BC + southern Ontario = direct seed or transplants. Anywhere = sets for green onions only.
What are the best onion varieties for Canada?
All long-day. **Yellow storage (the workhorses)**: Copra (extremely long storage 8-12 months, dense), Patterson (replaces Copra; Cornell-bred, high yield), Cortland (early, good for short Prairie season), Stuttgarter (heirloom, reliable, sets-compatible). **Yellow sweet (eat fresh, 3-5 month storage)**: Walla Walla (large mild, the classic), Yellow Sweet Spanish (giant 500 g bulbs), Ailsa Craig (heirloom large). **Red (slicing, eat fresh, 4-6 month storage)**: Red Wethersfield, Redwing (medium storage), Red Zeppelin. **White (mild, short storage 3-4 months)**: White Sweet Spanish, Sterling. **Specialty**: Cipollini (small flat Italian, roasting), Shallots (Frog Legs, Holland Red — perennial bulbs), Egyptian Walking Onions (perennial green onions for Prairie gardens, hardy to Zone 2). **By region**: Prairies + northern Canada lean Copra/Patterson/Cortland for storage. Ontario + Quebec all of the above. BC favours Walla Walla + Patterson. Maritimes Patterson + Copra. Where to buy: Veseys (PEI; sets, seed, transplants), William Dam (ON), West Coast Seeds (BC), Solana Seeds (QC), Eagle Creek (AB).
When do I harvest onions in Canada?
Late July through early September depending on zone + variety. **The signal**: tops have yellowed and 50%+ of the tops have flopped over at the neck. Don't bend tops over manually — that's an old myth that interrupts curing and shortens storage. Let them fall on their own. By zone + variety: **Coastal BC**: mid-July (early) to late August (storage). **Toronto/Niagara**: late July to mid-August (early), mid-August to early September (storage). **Ottawa/Montreal/Halifax**: early to mid August (early), late August to mid September (storage). **Prairies**: mid-August (early) to early September (storage). **How to harvest**: choose a dry day. Pull or fork up onions gently. Knock off loose soil; do NOT wash. Trim roots to 1 cm. Leave tops attached. Move immediately to curing. **Critical**: harvest before fall rains. Wet bulbs at harvest is the #1 cause of neck rot in storage.
How do I cure and store onions for winter?
Curing toughens the outer skin layers and dries the neck, making bulbs storable for months. **Cure (2-3 weeks)**: Lay or hang in a single layer in a dry well-ventilated shaded area at 20-30°C, 60-70% humidity. A garage, covered porch, shed, or attic works. Direct sun is too hot (cooks the bulbs). Damp basements grow mold. **Curing signals**: outer skin paper-dry and tight, neck dry and shrunken, tops fully brown halfway down. Use a fan to improve airflow indoors. **Trim + store (6-9 months)**: After curing, cut tops 2-3 cm above the bulb. Store at 0-4°C, 60-70% humidity, dark. Ideal containers: mesh bags, paper bags, braided strings, open crates — NEVER plastic (traps moisture). Best locations: unheated basement, root cellar, attached garage in mild winters, insulated shed. **Storage by variety**: Copra/Patterson/Stuttgarter 8-12 months. Walla Walla/Spanish 3-5 months. Red Wethersfield 4-6 months. White Spanish 3-4 months. **Check monthly**: remove any soft, sprouted, or moldy bulbs (one bad onion can ruin the whole bag). Do NOT store with potatoes (potatoes release moisture).
What is onion maggot and how do I prevent it?
Onion maggot (Delia antiqua) is the #1 onion pest in Canada, especially Ontario, Quebec, and the Maritimes. Adults are small grey flies that lay eggs at the base of onion plants in spring; larvae burrow into the bulb and roots, destroying the plant. Three generations per summer. **Symptoms**: leaves wilt + yellow, plants pull out easily (roots eaten away), small white maggots inside bulbs at harvest. **Prevention (rank-ordered)**: (1) Row cover from day of planting until early July — the most effective control. Adult flies cannot reach the plants to lay eggs. (2) Crop rotation — never plant onions/garlic/leeks in the same bed two years running; overwintering pupae emerge from previous Allium soil. (3) Diatomaceous earth ringed around plants in early spring deters egg-laying. (4) Transplants beat sets and direct seed — healthier larger plants tolerate light damage better. (5) Beneficial nematodes (Steinernema feltiae) applied to soil at planting in heavy-pressure areas. (6) Avoid composted manure near onions — attracts adult flies. (7) Onion + carrot interplanting confuses both onion maggot and carrot rust fly.
What are common Canadian onion problems?
Five most common. **(1) Onion maggot** — #1 pest, see dedicated FAQ. Row cover + rotation + transplants. **(2) Neck rot** (Botrytis) — soft watery rot at the neck of stored bulbs, weeks-to-months after harvest. Cause: harvested too wet, cured insufficiently, stored too humid. Prevention: harvest on dry day, cure 2-3 weeks until necks are bone-dry, store at 60-70% humidity. **(3) Bolting** (flower stalk forms, no bulb develops) — cause is temperature shock (cold spring after planting, then warmth) or stress (drought, then water). Sets are more prone than transplants. Fix: snap off flower stalks as soon as they appear (the plant may still form a small bulb); use transplants instead of sets; water consistently. Bolted onions don't store — eat immediately. **(4) Downy mildew** (Peronospora destructor) — pale-yellow leaf patches with grey fuzz underside, especially in wet humid Canadian summers. Spacing for airflow, water at soil level only, copper spray preventively in high-pressure areas (Maritimes, southern Ontario). **(5) Thrips** — tiny insects scrape leaf surfaces, leaving silvery streaks. Increase humidity (overhead spray in morning), insecticidal soap, predatory mites in greenhouses. Major issue mainly in hot dry summers (Prairies).