Cold hardiness & minimum temperature

Is Wisley Gaultheria (Gaultheria × wisleyensis)cold hardy? Hardiness zone & min temp

Also called Wisley gaultheria, Wisley prickly heath, Gaulnettya.

More about wisley gaultheria

About Wisley Gaultheria

Gaultheria × wisleyensis · also called Wisley gaultheria, Wisley prickly heath · flowering

A hybrid evergreen Ericaceae shrub raised at RHS Wisley, bearing small bell-shaped white or pink flowers in late spring followed by long-lasting purple-red berries. It thrives in moist, acidic, peaty soils in partial shade and forms a dense mound, making it an excellent year-round border or ground-cover plant for woodland gardens.

Cold limit: USDA 6–9 · RHS H5 (-15°C to 20°C)

What wisley gaultheria's hardiness rating actually means

Yes — wisley gaultheria is genuinely cold hardy. Rated RHS H5 and USDA 6–9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 6–9 — 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 about −15 to −10 °C. Wisley Gaultheria is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for wisley gaultheria as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 wisley gaultheria go outside or overwinter — and where?

Plant it out within USDA 6–9 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 wisley gaultheria can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Wisley Gaultheria hardiness — frequently asked questions

Is wisley gaultheria cold hardy?

Yes — wisley gaultheria is genuinely cold hardy. Rated RHS H5 and USDA 6–9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Wisley Gaultheria is hardy across USDA 6–9; 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 wisley gaultheria can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Wisley Gaultheria is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is wisley gaultheria?

Wisley Gaultheria is rated USDA 6–9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can wisley gaultheria survive winter outside?

Plant it out within USDA 6–9 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 wisley gaultheria below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.