How to Grow Three-cornered Leeks USA
On this page
Three-cornered leeks (Allium triquetrum) — 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.
Three-cornered Leek (Allium triquetrum)
7 sources cited · Verified
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Planting or division | 0 | Bulbs planted fairly deeply (PFAF). Propagate by seed, sown as soon as ripe in a greenhouse or cold frame -- germinates quickly -- or by division in summer after the plant has died down, with divisions replanted straight into their permanent position. NOTE: illegal to plant or cause to grow in the wild in Great Britain (RHS, Schedule 9) -- confine to a contained garden setting only, and check local regulations elsewhere. |
| Leaf growth | 3 | RHS: in leaf from February to July, narrow green leaves on distinctively triangular (three-cornered) stalks. |
| Flowering | 6 | RHS: in flower from spring to early summer, drooping white bell-shaped flowers with a central green vein on each petal. |
| Harvest & spread control | 8 | Bulbs harvested early summer, store at least six months; leaves and flowers picked while present. RHS/PFAF both note vigorous spread by seed and bulbils -- vigilant deadheading is recommended to prevent unwanted colonisation, and is a legal necessity, not just tidiness, given the Schedule 9 restriction. |
Quick Facts
| Factor | Value |
|---|---|
| Soil texture | Chalk, clay, loam or sand (RHS) |
| Drainage | Moist but well-drained |
| Lifecycle | herbaceous perennial |
| Edible parts | bulbs, leaves, flowers |
At a Glance
Harvest & Storage
When to pick: Bulbs (up to 20mm across) are harvested in early summer and store for at least six months (PFAF, tier 2). Leaves can be picked as a leek substitute at any point while present -- younger leaves raw, mature leaves cooked. Flowers are picked fresh for use as a garnish.
Diseases
Pests
Three-cornered Leek, Flower to Colony
Plan your Three-cornered Leeks planting
When to sow and plant Three-cornered Leeks depends on your own frost dates. Check the USA vegetable planting calendar. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.
Growing Three-cornered Leek 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 7 sources behind this guide (Environet UK, Plants For A Future (PFAF), Royal Horticultural Society) is in the references of our UK guide to three-cornered leeks; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
What problems affect three-cornered leeks?
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
Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.
Get the USA Garden Planner →Instant PDF download · Written for US 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 USDA hardiness-zone and frost-date data, with Cooperative 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.
Last verified 2026-09-02
Related guides
More from the same group (the onion family):
Growing advice for your part of the USA
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.