Cold hardiness & minimum temperature

Is Keisk's Leucothoe (Leucothoe keiskei)cold hardy? Hardiness zone & min temp

Also called Keisk's leucothoe, Keiskei fetterbush, Japanese leucothoe.

More about keisk's leucothoe

About Keisk's Leucothoe

Leucothoe keiskei · also called Keisk's leucothoe, Keiskei fetterbush · flowering

A compact, low-growing Japanese Ericaceae shrub producing elegant pendulous racemes of white flowers in late spring. More cold-hardy than most leucothoe species and finer-textured in leaf, its glossy evergreen foliage turns red in autumn and winter in good light. Suited to rock gardens, shaded borders, and acidic container planting in USDA zones 5–8.

Cold limit: USDA 5–8 · RHS H5 (-27°C to 25°C)

Watch for — Poor winter colour in deep shade: The attractive red winter foliage colour only develops with some light exposure. Deep shade produces uniformly green leaves year-round. Move container plants to a brighter, frost-protected position in autumn to enhance the seasonal display.

What keisk's leucothoe's hardiness rating actually means

Yes — keisk's leucothoe is genuinely cold hardy. Rated RHS H5 and USDA 5–8, 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 5–8 — 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 about −15 to −10 °C. Keisk's Leucothoe is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for keisk's leucothoe 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 keisk's leucothoe go outside or overwinter — and where?

Plant it out within USDA 5–8 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 keisk's leucothoe can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Keisk's Leucothoe hardiness — frequently asked questions

Is keisk's leucothoe cold hardy?

Yes — keisk's leucothoe is genuinely cold hardy. Rated RHS H5 and USDA 5–8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Keisk's Leucothoe is hardy across USDA 5–8; 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 keisk's leucothoe can survive?

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

What hardiness zone is keisk's leucothoe?

Keisk's Leucothoe is rated USDA 5–8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can keisk's leucothoe survive winter outside?

Plant it out within USDA 5–8 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 keisk's leucothoe 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.