Cold hardiness & minimum temperature

Is Crown Vetch (Coronilla varia)cold hardy? Hardiness zone & min temp

Also called Crown Vetch, Purple Crown Vetch, Axseed.

More about crown vetch

About Crown Vetch

Coronilla varia · also called Crown Vetch, Purple Crown Vetch · flowering

Crown Vetch is a sprawling, nitrogen-fixing perennial legume native to Europe and western Asia, widely planted in North America for erosion control on roadsides and slopes and listed as invasive in several US states. It produces dense heads of pink-purple and white pea-like flowers from June to August and spreads aggressively via rhizomes and self-seeding, quickly out-competing native vegetation. The most important consideration in garden use is its invasive potential — site carefully and contain its spread. Crown Vetch is toxic to horses and should be treated as mildly toxic for cats and dogs.

Cold limit: USDA 3-9 · RHS H7 (-25 to 35 °C)

What crown vetch's hardiness rating actually means

Yes — crown vetch is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 3-9 — 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 below about −20 °C. Crown Vetch is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for crown vetch as it gets too cold:

It tolerates winter lows to about −20 °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 crown vetch go outside or overwinter — and where?

Plant it out within USDA 3-9 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 crown vetch can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Crown Vetch hardiness — frequently asked questions

Is crown vetch cold hardy?

Yes — crown vetch is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Crown Vetch is hardy across USDA 3-9; 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 crown vetch can survive?

Minimum survivable temperature is roughly below about −20 °C. Crown Vetch is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is crown vetch?

Crown Vetch is rated USDA 3-9 and RHS H7 — Hardy in the severest European continental winters.

Can crown vetch survive winter outside?

Plant it out within USDA 3-9 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 crown vetch below its minimum temperature?

It tolerates winter lows to about −20 °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.