How to Grow Tree Onions Canada
On this page
Tree onions (Allium x proliferum) — 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.
Tree Onion (Allium x proliferum)
5 sources cited · Verified
Soil & Growing Conditions
Water: About 1in of water a week; MSU notes it does not thrive in wet or extremely heavy soils.
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Planting bulbils | 0 | Plant bulbils (topsets) 2in deep in full sun. Fall is the optimal planting season, though Penn State notes they can go in spring, summer, fall or winter as long as the ground is not frozen. Larger bulblets establish better than smaller ones (MSU). |
| Establishment & overwintering | 3 | A hardy perennial to zone 3 that stays green through winter (MSU) -- unlike most alliums it does not need to be lifted or protected for the cold months. |
| Leaf & topset development | 6 | Hollow leaves can be cut and used like chives or green onions at any point. Through summer the plant sends up a flowering stem that produces a cluster of bulbils (topsets) instead of a normal flower, green at first. |
| Topsets mature & the plant "walks" | 8 | Topsets turn reddish or purple as they mature (Penn State) and can be picked at that point. Left in place, the stem eventually dries, weakens and topples under their weight, and the bulbils root wherever they land -- moving the plant roughly 2-3ft (Penn State) to about one stem-length (MSU) across the garden each year. The underground parent bulb can also be harvested, though it ends further growth from that spot. |
Quick Facts
| Factor | Value |
|---|---|
| Soil texture | Loamy sand or sandy loam (MSU) |
| Drainage | Free-draining |
| Lifecycle | herbaceous perennial |
| Edible parts | leaves, bulbils, bulbs |
At a Glance
Harvest & Storage
When to pick: Topsets can be picked once they colour from green to reddish or purple (Penn State). Leaves can be cut like chives or green onions at any point while green. The underground parent bulb is edible but tough-skinned and pungent (MSU), and lifting it ends further growth from that plant.
Diseases
Pests
Tree Onion, Topset to Walk
Plan your Tree Onions planting
When to sow and plant Tree 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 Tree 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 5 sources behind this guide (Michigan State University Extension, Penn State Extension, Royal Horticultural Society and others) is in the references of our UK guide to tree onions; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
What problems affect tree onions?
Our data links 1 disease and 1 pest 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 2026-09-02
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.