Cool-season biennial allium grown for thick blanched stems. Tolerates hard frost in the ground — a useful winter vegetable.
Hardiness ratings
| System | Rating | Temperature range | How to read it |
|---|---|---|---|
| USDA hardiness zone | Zone 4–9 | −34.4 °C to −1.1 °C | Zones where it can be grown as an annual — not a frost-tolerance rating |
| RHS hardiness rating | H7 | down to −20 °C | Plant needs at least this level of cold tolerance |
| Canadian plant hardiness zone | Zone 4–9 | −29 °C and warmer | Zones where it can be grown as an annual — not a frost-tolerance rating |
| Australian (ANBG) zone | Zone 1–5 | −15 °C to 10 °C | Zones where it can be grown as an annual — not a frost-tolerance rating |
As a tender annual, Leek doesn't overwinter — the zone range shows where the growing season supports it. See the RHS rating for its actual cold tolerance.
About Leek
Leeks are alliums grown for their thickened leaf bases rather than a bulb, and the white shaft that gets eaten is produced by earthing up or deep planting to exclude light — a leek left unblanched is perfectly edible but far more green and much less tender. They are among the hardiest vegetables in common cultivation, standing through cold that finishes most crops, which historically made them valuable as a winter staple. The leek is the national emblem of Wales, a tradition with a long documented history.
Growing notes
- Hardiest leek cultivars (Bandit, Bleu de Solaise) overwinter through deep frost
- Earth up the stems progressively as they grow to lengthen the white blanched section
Pet caution: Leek is listed as potentially harmful to cats and/or dogs. Keep pets from grazing on it, and contact a vet if you suspect your animal has eaten some.
Categories
Related plants
Cross-check Leek against your zones