When to Plant Onions in BC
Indoor seed dates, set planting dates, long-day variety selection, pest and disease control, and curing and storage for Vancouver, Victoria, Kelowna, Kamloops, and Prince George.
When to plant onions in BC starts earlier than almost any other vegetable in the garden — Victoria gardeners sow seeds indoors before the calendar turns to January. Onions need the longest indoor start of any common BC crop, and getting that start date right is what determines whether you harvest large, well-cured storage bulbs or thin, undersized ones that rot within weeks.
This guide covers indoor seed start dates and set planting dates for every major BC city, why long-day variety selection is non-negotiable in BC, the difference between growing from seed versus sets, best varieties by zone, how to grow and cure onions, and the pests and diseases BC onion growers encounter most.
BC onions at a glance: Long-day varieties only — short-day varieties will not bulb in BC. From seed: start indoors Dec–Feb depending on city. Sets: plant outdoors as soon as soil is workable. Harvest when half the tops fall over. Cure 2–3 weeks before storing. Onion fly row cover from planting through June.
Outside BC? See the Canada-wide onion planting guide for dates in Ontario, Quebec, the Prairies, and the Maritimes.
BC Onion Planting Dates by City — 2026
Onions started from seed need 10–12 weeks indoors before transplanting. Sets can go directly into the ground as soon as soil is workable above 10°C. Both methods target the same transplant or planting window.
| City | Start Indoors | Transplant Out | Sets Direct | Harvest |
|---|---|---|---|---|
| Victoria | Dec 20–Jan 10 | Mar 1–20 | Feb 15–Mar 20 | Jul–Aug |
| Vancouver | Jan 1–20 | Mar 10–Apr 1 | Mar 1–Apr 1 | Aug |
| Kelowna | Jan 15–Feb 1 | Apr 1–15 | Mar 15–Apr 15 | Aug–Sept |
| Kamloops | Jan 20–Feb 5 | Apr 5–20 | Apr 1–20 | Aug–Sept |
| Prince George | Feb 1–20 | Apr 20–May 5 | Apr 15–May 1 | Aug–Sept |
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🌿 Free Seed Starting CalculatorDay Length — The Rule That Determines Everything
Onions form bulbs in response to day length, not temperature. Getting this wrong — planting the wrong type — results in no bulb at all, regardless of how well you tend the plants.
Long-day onions — the only type for BC
Long-day onion varieties bulb when days reach 14–16 hours of light. Across all of BC, this threshold is crossed in June — coastal BC in early June, interior BC by mid-June. The plant will grow green tops through the spring, then trigger bulb formation once the critical day length is reached. This is the correct behaviour for BC's latitude. All onion seed and sets sold at BC garden centres should be long-day varieties — confirm this on the packet before buying.
Short-day onions — will not work in BC
Short-day varieties (bred for Texas, Georgia, and other southern US states) bulb at only 10–12 hours of daylight. By the time BC days are short enough to trigger bulbing in these varieties — October or November — it is far too late in the season for bulb development. The plant simply continues producing tops and never bulbs. This is one of the most common and frustrating onion failures in BC — caused entirely by purchasing seed or sets without checking the day-length type. The words "Vidalia," "Texas Sweet," or "Bermuda" are reliable signals that a variety is short-day and unsuitable for BC.
Intermediate day-length onions — for Prince George
Intermediate (or day-neutral) varieties bulb at 12–14 hours and work across a wider latitude range. For Prince George and other short-season BC zones, intermediate varieties like Candy (85 days) mature faster than standard long-day types and are a reliable choice for the tighter growing window. Candy will also work in all southern BC zones. All strictly long-day varieties work across all BC latitudes — the day-length threshold is comfortably met at Prince George's latitude by mid-June.
Seed, Sets, or Transplants — Which to Use in BC
From seed indoors — best results, most effort
Starting from seed gives access to the best storage and sweet varieties not available as sets, produces the largest bulbs, and results in plants that are less prone to bolting than set-grown onions. Sow into 72-cell trays using sterile seed-starting mix, 2–3 seeds per cell, 6 mm deep. Thin to one seedling per cell after germination. Onion seedlings grow slowly — they look like thin grass for weeks before thickening up. Grow lights running 14–16 hours are essential for December and January starts in coastal BC's weak winter light. Pot up into 8 cm pots once seedlings reach pencil thickness. Harden off for 10–14 days before transplanting — onions tolerate light frost once hardened.
From sets — easiest, most available
Sets are small dormant onion bulbs, typically Stuttgarter or a similar long-day storage variety, sold in bags at BC garden centres from February onward. Plant them 2–3 cm deep, 10 cm apart, as soon as soil is workable. They establish quickly without the indoor start. The tradeoffs: sets have a limited variety range, produce smaller average bulbs than seed-grown onions, and are more prone to bolting — especially if planted into cold soil or left in storage too long before planting. Choose firm, small sets (coin-sized or smaller) over large ones; large sets are more likely to bolt. Discard any that feel soft or show signs of mold.
From transplants — a middle path
Some BC garden centres sell onion transplants (bundles of bare-root seedlings) in March and April — typically Walla Walla Sweet or a similar variety. These offer the benefits of seed-grown onions without the January indoor start. Transplants establish well when planted at pencil thickness, 10 cm apart, with roots tucked in and the white base just at soil level. If purchasing transplants, look for bundles where seedlings are uniform in size, not tangled or yellowing. Avoid transplants that are thicker than a finger — they have likely been held too long and are more prone to bolting.
Best Onion Varieties for BC
All varieties below are long-day types and appropriate for BC. Intermediate-day varieties are noted where relevant for Prince George and short-season zones.
| Variety | Days | Type | Best Use | Notes |
|---|---|---|---|---|
| Candy | 85 days | Intermediate | All zones | Fastest-maturing reliable option. Best choice for Prince George. Mild flavour, moderate storage (2–3 months). |
| Stuttgarter | 100 days | Long-day / sets | All zones | Standard BC set variety. Widely available. Flat globe shape. Good storage. Most practical choice for sets growers. |
| Copra | 105 days | Long-day | Storage | Best-keeping variety available — cures hard, stores 6–8 months. The top choice if long storage is the goal. |
| Patterson | 105 days | Long-day | Storage | Top commercial storage onion grown in BC's Fraser Valley. Excellent disease resistance. 6–8 months storage life. |
| Walla Walla Sweet | 110 days | Long-day | Fresh use | Mild, very sweet, large bulbs. From the neighbouring Washington valley. Excellent for interior BC. Short storage (1–2 months). |
| Ailsa Craig | 110 days | Long-day | Coastal / fresh | Grows very large globe bulbs in coastal BC's long spring season. Mild flavour, poor storage — eat within 2 months. |
| Red Baron | 105 days | Long-day | All zones | Best reliable red onion for BC. Deep burgundy colour, good storage (3–4 months). Widely available as seed. |
How to Grow Onions in BC
Soil and drainage
Onions prefer loose, well-drained soil with a pH of 6.2–6.8. They perform poorly in compacted or waterlogged ground — bulb development is stunted and rot pressure increases dramatically. In coastal BC's wet spring conditions, raised beds or well-mounded rows are not optional; they are the difference between a successful crop and a rotted one. Work in aged compost before planting but avoid fresh manure, which promotes lush tops at the expense of bulb development and increases disease risk. Onions have shallow, fibrous roots — keep the bed weed-free, as competition from weeds significantly reduces bulb size. Hand weed carefully rather than hoeing to avoid damaging shallow roots.
Spacing and planting depth
Space onions 10 cm apart in rows 25–30 cm apart for full-size bulbs. Closer spacing produces smaller bulbs but is useful for green onion (scallion) harvesting from thinnings. Plant sets 2–3 cm deep with the pointed tip just at or barely above the soil surface — planting too deep encourages rot and delays establishment. Plant transplants so the white base is just at soil level and roots are fully covered. As bulbs develop through summer they will push themselves slightly out of the ground — this is normal and correct; do not hill soil over developing bulbs.
Watering and fertilising
Water consistently through spring and early summer — 2–3 cm per week. In coastal BC, rainfall often covers spring irrigation needs, but the dry July–August period in all BC zones requires regular watering during the bulbing stage. Stop watering entirely once tops begin to yellow and fall — at this point the plant is curing the bulb and excess moisture encourages neck rot. Fertilise with a balanced fertiliser (10-10-10) at planting. Apply a second nitrogen-rich feed when leaves are pencil-width and actively growing. Stop all nitrogen fertilising by midsummer — late nitrogen pushes soft, thick necks that do not cure and cure poorly in storage.
Harvest and curing
Harvest when at least half the tops have fallen over naturally — do not bend them deliberately, as this introduces neck damage and rot. After the tops fall, leave bulbs in the ground for 1–2 more weeks for in-ground curing if weather is dry. In coastal BC's often damp August, pull bulbs and cure on slatted racks or greenhouse staging in warm, moving air (25–30°C) for 2–3 weeks. The neck must be fully dry and papery before moving to storage. Never store uncured onions — moisture in the neck is the primary cause of storage rot. Do not wash before curing; brush off loose soil only.
Pests and Diseases in BC
BC's wet coastal climate creates specific disease pressure for onions — downy mildew and neck rot are more problematic here than in drier provinces. Onion fly is the primary pest and is manageable with row cover.
Onion fly — the primary BC pest
The onion fly (Delia antiqua) lays eggs at the base of onion stems in spring. Larvae tunnel into the bulb, causing plants to collapse and rot from the inside out. In coastal BC the onion fly has multiple generations per season, with the first and most damaging emergence in May and June. Row cover (floating fabric) installed at planting and sealed at the edges is the most effective control — keep it in place through late June. There is no practical spray control once larvae are inside the bulb. Crop rotation reduces but does not eliminate pressure, as the fly can travel significant distances. Inspect plants regularly — wilting of individual plants surrounded by healthy ones is the first sign of infestation.
Downy mildew
Downy mildew (Peronospora destructor) appears as pale oval patches on leaves that develop a gray-purple fuzzy coating in humid conditions — common during coastal BC's cool, wet spring periods. It spreads rapidly in still, damp air and can defoliate an onion bed in 2–3 weeks during a wet June. Prevention: space plants at the recommended 10 cm apart (not closer), water at the base only, and avoid working in the bed when plants are wet. Copper-based fungicide applied preventively every 7–10 days during prolonged wet periods slows spread. Infected tops reduce bulb size substantially as the plant loses its photosynthetic capacity before bulbing is complete.
White rot and neck rot
White rot (Sclerotium cepivorum) causes white fluffy mycelium at the base of the bulb, yellowing tops, and plant death — and like clubroot, persists in soil for 20+ years once established. It is more prevalent in BC's cool, moist coastal soils than in drier provinces. There is no cure once it appears. Prevention: strict 4-year rotation of all alliums (onions, garlic, leeks); never bring soil or transplants from infected beds; maintain soil pH above 6.5. Neck rot (Botrytis allii) is a storage disease that enters through damaged or poorly cured necks — appearing as gray mold inside stored bulbs months after harvest. Prevention is entirely in the cure: ensure necks are fully dry and papery before storage.
Common Onion Problems in BC
No bulb forming
The most common cause is wrong variety — short-day onions planted in BC will produce abundant tops but never bulb at BC's latitudes. Check variety descriptions before purchasing. A second cause is starting seeds too late: onions need maximum top growth before the day-length trigger arrives in June — a small plant with few leaves when bulbing is triggered will produce a small bulb. This is why the December–January start dates for coastal BC are not conservative — they are the minimum needed to build a plant large enough to produce a full-size bulb by harvest.
Bolting — seed stalks instead of bulbs
Bolting is triggered by vernalisation — seedlings or sets that experience temperatures below 10°C after reaching pencil thickness interpret the cold as winter and send up a flower stalk instead of forming a bulb when days lengthen. In BC this happens most commonly with: sets planted into cold soil in early spring before soil has warmed; over-thick transplants that were held too long before planting; or seed-grown plants that experienced a prolonged cold period during indoor growing. A bolted onion will not form a usable storage bulb — the flower stalk makes the inside of the bulb hard and inedible. Use bolted onions immediately as green onions. Sets smaller than a coin are less likely to bolt than large ones.
Small bulbs
Small bulbs at harvest are usually caused by one or more of: starting too late indoors (insufficient top growth before bulbing trigger); planting too closely (competition reduces bulb size); nitrogen fertiliser applied too late in the season (pushes top growth when the plant should be bulbing); or weed competition throughout the season. The number of leaves a plant has at the point the day-length trigger is reached directly determines bulb size — each leaf corresponds roughly to one ring inside the bulb. A plant with 13 healthy leaves can form a 13-ring bulb; a plant with 8 leaves is limited to 8. This is why the early start date and consistent feeding through spring are so important for BC onion growers.
Frequently Asked Questions
When should I plant onions in BC?
From seed indoors: Victoria December 20–January 10, Vancouver January 1–20, Kelowna/Kamloops January 15–February 5, Prince George February 1–20. Transplant out 10–12 weeks later. Sets direct in ground: Victoria/Vancouver February 15–April 1, Kelowna/Kamloops March 15–April 20, Prince George April 15–May 1. Harvest when at least half the tops fall over, typically August–September.
Why did my onions grow lots of tops but no bulbs?
Almost certainly a wrong variety — short-day onions will not bulb in BC. Check that your variety or set is labelled long-day. The second cause is starting seeds too late, giving the plant insufficient leaf development before the June day-length bulbing trigger. A large, leafy plant produces a large bulb; a small plant produces a small one.
Are sets or seeds better for BC onions?
Sets are easier and need no indoor space — they are the practical choice for most home gardeners. Seeds give access to better storage varieties (Copra, Patterson), produce larger bulbs, and are less prone to bolting. If you have the setup for a January indoor start with grow lights, seed-grown onions consistently outperform sets in coastal BC's long season.
How do I prevent onion fly damage in BC?
Row cover (floating fabric) installed at planting and sealed at the edges, kept in place through late June, is the only reliable prevention. There is no effective spray once larvae are inside the bulb. Remove row cover carefully when plants need thinning or weeding, replace it immediately, and ensure edges stay sealed. Crop rotation reduces long-term pressure but the fly travels far enough that it cannot be avoided by rotation alone.
Can I start onions indoors without a grow light in BC?
For February starts and later, a very bright south-facing window may produce acceptable seedlings. For December and January starts required by Victoria and Vancouver gardeners, a grow light running 14–16 hours per day is needed — winter daylight in coastal BC is insufficient for compact, well-developed onion seedlings. Leggy, weak seedlings from inadequate light translate directly into smaller bulbs at harvest.
How long do BC-grown onions store?
Storage life depends heavily on variety and curing quality. Copra and Patterson store 6–8 months at 0–5°C when properly cured. Red Baron stores 3–4 months. Sweet varieties (Walla Walla, Ailsa Craig) store only 1–2 months and should be used first. In coastal BC's often damp conditions, thorough curing — 2–3 weeks in warm moving air until necks are completely dry and papery — is the most important factor in storage life. Improperly cured onions begin rotting within weeks regardless of variety.