How to Grow Potato Onions Canada
On this page
Potato onions (Allium cepa var. aggregatum) — bulbous herbaceous perennial.
Unlike an annual crop, the work here is front-loaded into establishment: get the planting and the site right and the same plants crop for several seasons.
Core growing advice on this page is checked against named horticultural sources — see References.
Potato Onion (Allium cepa var. aggregatum)
2 sources cited · Verified
Soil & Growing Conditions
Water: well-drained, organically rich (Cultivariable)
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Planting | 0 | Plant bulbs late September to mid-October for larger spring bulbs, or late March to April for less bolting risk; thin to 4-6in spacing (UMD Extension). Plant with the bulb tip at the surface in mild climates, deeper in cold climates for protection (Cultivariable). |
| Establishment | 3 | Long-day plant needing long summer days (north of 37N or south of 37S) to bulb well; prefers mildly acidic to neutral pH, organically rich, well-drained soil (Cultivariable). Mulch fall-planted bulbs against weeds and extreme cold (UMD Extension). |
| Bulb multiplication | 3 | Divides underground into a cluster or "hill" of typically six to eleven daughter bulbs -- the multiplier habit that distinguishes it from single-bulb onions (Cultivariable). |
| Harvest | 8 | Gently dig or pull once tops die back and fall over, usually July-August (UMD Extension, Cultivariable); leaves can be snipped as green onions year-round if limited to 10% of the plant. |
Quick Facts
| Factor | Value |
|---|---|
| Soil texture | organically rich, well-drained (Cultivariable) |
| Drainage | well-drained |
| Lifecycle | bulbous herbaceous perennial |
| Edible parts | bulbs, leaves |
At a Glance
Harvest & Storage
When to pick: Gently dig or pull once the tops start to die back and fall over (UMD Extension); usually July-August but can be harvested anytime after bulbing with quality holding through winter (Cultivariable). Store at 50-60°F (10-16°C) and low humidity -- often keeps more than a year in an open box in a cool pantry, notably better storage than shallots.
Diseases
Pests
Potato Onion, Cluster to Harvest
Plan your Potato Onions planting
When to sow and plant Potato Onions depends on your own frost dates. Check the Canada vegetable planting calendar. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.
Growing Potato Onion in another region
Sowing dates, frost timing and local advice differ by country. Use the guide for where you garden.
Sources
The full list of 2 sources behind this guide (Cultivariable, University of Maryland Extension) is in the references of our UK guide to potato onions; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
What problems affect potato onions?
Our data links 1 disease and 2 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Short-season growing is arithmetic before it is technique: days to maturity against frost-free days decides what will finish at all. The Canada Garden Planner does that subtraction for your region before you sow.
Get the Canada Garden Planner →Instant PDF download · Written for Canadian growing conditions
How this guide is put together
The growing data on this page — sowing windows, pests, diseases, soil and site requirements — comes from named horticultural sources, listed in References below, checked against Canadian hardiness-zone and frost-date data, with provincial agriculture and university extension sources cited directly where one exists for a crop. An automated pipeline assembles that verified data into the page you're reading: it selects which facts to lead with and builds the surrounding prose and layout. It does not invent a date, a source or a number — where a verified value for a field isn't available, the page leaves it out rather than guessing. A person reviews and publishes each page; nothing goes live unverified.
Vegetable Growing Guides Canada
Last verified 2026-08-28
Related guides
More from the same group (the onion family):
Growing advice for your part of Canada
Timing and conditions change a lot inside one country. These guides cover frost dates and growing seasons region by region.
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Keep going
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.