Cold hardiness & minimum temperature

Is Comfrey-Leaved Rock Rose (Cistus symphytifolius)cold hardy? Hardiness zone & min temp

Also called Comfrey-leaved rock rose, Canary Island rock rose.

More about comfrey-leaved rock rose

About Comfrey-Leaved Rock Rose

Cistus symphytifolius · also called Comfrey-leaved rock rose, Canary Island rock rose · flowering

Cistus symphytifolius is an upright, tall-growing evergreen shrub endemic to the Canary Islands (Gran Canaria, Tenerife, La Palma), where it colonises dry Canary pine forest and scrubland at altitude; it is also known as Cistus vaginatus. It produces large, vivid deep-pink flowers up to 6 cm across in spring and early summer, making it one of the most ornamental rock roses. As a Canary Islands endemic adapted to mild, relatively frost-free winters, it is tender and only suited to the mildest UK gardens or a frost-free greenhouse; this frost sensitivity is the single most critical care fact. Cistus is not listed on the ASPCA toxic plant database; classified mildly-toxic here as a precaution.

Cold limit: USDA 9-11 · RHS H2 (2 to 35°C)

Watch for — Frost damage: The primary threat in the UK and cool US climates. Even brief temperatures below 0°C can blacken and kill stems; a hard frost below -2°C may be fatal. Protect with horticultural fleece over winter, grow against a warm south wall, or overwinter in a frost-free greenhouse.

What comfrey-leaved rock rose's hardiness rating actually means

Comfrey-Leaved Rock Rose is half-hardy (RHS H2). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Its RHS rating of H2 means: Tender — survives a frost-free greenhouse or a very mild, sheltered spot. On the US scale that maps to USDA 9-11 — 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 1 to 5 °C — tolerates cold but no real frost. Comfrey-Leaved Rock Rose shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for comfrey-leaved rock rose as it gets too cold:

Down to roughly about 1 to 5 °C it copes, especially if dry and sheltered.
A sustained hard frost collapses the top growth; whether it returns depends on whether the roots, crown or tubers froze.
Wet cold is far more lethal than dry cold for this plant — soggy, frozen soil is the usual killer.

Can comfrey-leaved rock rose go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 or a frost-free UK microclimate.
In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter.
A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

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 comfrey-leaved rock rose can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H2 figure above.

Frost protection for borderline comfrey-leaved rock rose

Comfrey-Leaved Rock Rose is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost.
Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse.
Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones.
Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.

Comfrey-Leaved Rock Rose hardiness — frequently asked questions

Is comfrey-leaved rock rose cold hardy?

Comfrey-Leaved Rock Rose is half-hardy (RHS H2). It survives a mild winter outdoors in a sheltered spot, but a hard frost kills it — so in colder zones it is lifted, potted, or grown as a tender plant. Borderline outdoors. In its mild end of USDA 9-11 (and sheltered UK gardens) comfrey-leaved rock rose can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature comfrey-leaved rock rose can survive?

Minimum survivable temperature is roughly about 1 to 5 °C — tolerates cold but no real frost. Comfrey-Leaved Rock Rose shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is comfrey-leaved rock rose?

Comfrey-Leaved Rock Rose is rated USDA 9-11 and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can comfrey-leaved rock rose survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 or a frost-free UK microclimate. In colder zones, grow it in a pot you can move under cover, or lift its tubers/roots and store them frost-free over winter. A south-facing wall, free-draining soil and a dry winter position can push it a full zone hardier than the books suggest.

How do I protect comfrey-leaved rock rose from frost?

Mulch the crown or root zone deeply with bark, straw or leaf-mould before the first hard frost. Move container plants against a warm wall or into an unheated but frost-free porch or greenhouse. Fleece the top growth on the coldest nights, and keep it on the dry side — dry roots survive cold far better than wet ones. Lift dahlia-type tubers or tender crowns after the first light frost blackens the foliage and store them somewhere cool but frost-free.