Cold hardiness & minimum temperature

Is Diana Rose of Sharon (Hibiscus syriacus 'Diana')cold hardy? Hardiness zone & min temp

Also called Diana Rose of Sharon, Shrub Althaea, Hardy Hibiscus 'Diana'.

More about diana rose of sharon

About Diana Rose of Sharon

Hibiscus syriacus 'Diana' · also called Diana Rose of Sharon, Shrub Althaea · flowering

A late-flowering deciduous shrub producing large, pure-white, slightly ruffled single flowers from late summer well into autumn — one of the latest garden shrubs to bloom. 'Diana' is an upright, vigorous cultivar that brings welcome colour when most other shrubs have finished. ASPCA lists Hibiscus syriacus as non-toxic to dogs and cats.

Cold limit: USDA 5-9 · RHS H5 (-15 to 38°C)

What diana rose of sharon's hardiness rating actually means

Yes — diana rose of sharon is genuinely cold hardy. Rated RHS H5 and USDA 5-9, 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 5-9 — 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. Diana Rose of Sharon is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for diana rose of sharon 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 diana rose of sharon go outside or overwinter — and where?

Plant it out within USDA 5-9 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 diana rose of sharon can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Diana Rose of Sharon hardiness — frequently asked questions

Is diana rose of sharon cold hardy?

Yes — diana rose of sharon is genuinely cold hardy. Rated RHS H5 and USDA 5-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Diana Rose of Sharon is hardy across USDA 5-9; 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 diana rose of sharon can survive?

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

What hardiness zone is diana rose of sharon?

Diana Rose of Sharon is rated USDA 5-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can diana rose of sharon survive winter outside?

Plant it out within USDA 5-9 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 diana rose of sharon 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.