Cold hardiness & minimum temperature

Is Spring Onion (Allium fistulosum 'White Lisbon')cold hardy? Hardiness zone & min temp

Also called White Lisbon spring onion, scallion, green onion.

More about spring onion

About Spring Onion

Allium fistulosum 'White Lisbon' · also called White Lisbon spring onion, scallion · edible

Spring onions are quick, non-bulbing alliums grown for their slim white shanks and hollow green tops, eaten whole and raw. 'White Lisbon' is the classic fast, hardy variety, ready in roughly eight weeks from sowing and good for succession crops or overwintering for an early spring pick. They need little space and crop heavily from a short row.

Cold limit: USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones) · RHS H4 (10-24°C)

Watch for — Slow germination in cold soil: Seed sown into cold wet ground rots or germinates patchily. Wait for soil to warm, or sow in modules and transplant in clumps.

What spring onion's hardiness rating actually means

Yes — spring onion is genuinely cold hardy. Rated RHS H4 and USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones) — the zones where it can be left outdoors year-round.

New to these scales? The USDA hardiness zone map explained covers how the zone numbers work, and you can find your own zone with the zone finder.

Minimum temperature — and what happens below it

Minimum survivable temperature is roughly about −10 to −5 °C. Spring Onion is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for spring onion as it gets too cold:

It tolerates winter lows to about −10 to −5 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can spring onion go outside or overwinter — and where?

Plant it out within USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

Work back from your local frost dates with the frost-date calculator: the last spring frost and first autumn frost are what really decide when spring onion can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Spring Onion hardiness — frequently asked questions

Is spring onion cold hardy?

Yes — spring onion is genuinely cold hardy. Rated RHS H4 and USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Spring Onion is hardy across USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature spring onion can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. Spring Onion is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is spring onion?

Spring Onion is rated USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can spring onion survive winter outside?

Plant it out within USDA 3-9 ('White Lisbon Winter Hardy' overwinters in milder zones) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to spring onion below its minimum temperature?

It tolerates winter lows to about −10 to −5 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.