Cold hardiness & minimum temperature

Is One-flowered Clintonia (Clintonia uniflora)cold hardy? Hardiness zone & min temp

Also called One-flowered Clintonia, Queen's Cup, Bride's Bonnet, Bead Lily.

More about one-flowered clintonia

About One-flowered Clintonia

Clintonia uniflora · also called One-flowered Clintonia, Queen's Cup · flowering

A delicate western North American woodland perennial bearing solitary white flowers above a pair of broad glossy leaves in late spring, followed by a single cobalt-blue berry. Native to cool, moist montane conifer forests from Alaska to California. Best in deep shade with acidic, humus-rich soil and cool summer temperatures.

Cold limit: USDA 4-8 · RHS H7 (1–22°C)

What one-flowered clintonia's hardiness rating actually means

Yes — one-flowered clintonia is genuinely cold hardy. Rated RHS H7 and USDA 4-8, 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 4-8 — 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. One-flowered Clintonia is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for one-flowered clintonia 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 one-flowered clintonia go outside or overwinter — and where?

Plant it out within USDA 4-8 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 one-flowered clintonia can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

One-flowered Clintonia hardiness — frequently asked questions

Is one-flowered clintonia cold hardy?

Yes — one-flowered clintonia is genuinely cold hardy. Rated RHS H7 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. One-flowered Clintonia is hardy across USDA 4-8; 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 one-flowered clintonia can survive?

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

What hardiness zone is one-flowered clintonia?

One-flowered Clintonia is rated USDA 4-8 and RHS H7 — Hardy in the severest European continental winters.

Can one-flowered clintonia survive winter outside?

Plant it out within USDA 4-8 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 one-flowered clintonia 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.