Cold hardiness & minimum temperature

Is Leatherleaf (Chamaedaphne calyculata)cold hardy? Hardiness zone & min temp

Also called Leatherleaf, Cassandra, Leatherleaf bogrosemary.

More about leatherleaf

About Leatherleaf

Chamaedaphne calyculata · also called Leatherleaf, Cassandra · flowering

Leatherleaf is a circumpolar evergreen shrub of sphagnum bogs and fens, among the first shrubs to bloom in spring with chains of small white urn-shaped flowers along arching stems. Its leathery, rust-scaled leaves provide year-round structure. Hardy and bog-adapted, it is ideal for acidic, wet native gardens in cool climates. Contains grayanotoxins — toxic to pets.

Cold limit: USDA 2–6 · RHS H7 (−40 to 25 °C)

Watch for — Phytophthora root rot in stagnant water: Although moisture-loving, stagnant non-aerated water with warm summer temperatures promotes Phytophthora. Ensure gentle water movement through the bog bed. Avoid black plastic-lined containers that heat water in summer — use light-coloured or insulated bog containers.

What leatherleaf's hardiness rating actually means

Yes — leatherleaf is genuinely cold hardy. Rated RHS H7 and USDA 2–6, 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 2–6 — 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. Leatherleaf is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for leatherleaf 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 leatherleaf go outside or overwinter — and where?

Plant it out within USDA 2–6 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 leatherleaf can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Leatherleaf hardiness — frequently asked questions

Is leatherleaf cold hardy?

Yes — leatherleaf is genuinely cold hardy. Rated RHS H7 and USDA 2–6, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Leatherleaf is hardy across USDA 2–6; 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 leatherleaf can survive?

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

What hardiness zone is leatherleaf?

Leatherleaf is rated USDA 2–6 and RHS H7 — Hardy in the severest European continental winters.

Can leatherleaf survive winter outside?

Plant it out within USDA 2–6 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 leatherleaf 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.