Cold hardiness & minimum temperature

Is Orache-Leaved Sun Rose (Halimium atriplicifolium)cold hardy? Hardiness zone & min temp

Also called Orache-Leaved Sun Rose, White-Leaved Sun Rose.

More about orache-leaved sun rose

About Orache-Leaved Sun Rose

Halimium atriplicifolium · also called Orache-Leaved Sun Rose, White-Leaved Sun Rose · flowering

Halimium atriplicifolium is an evergreen shrub in the Cistaceae family native to southern Spain and northern Morocco, distinguished by its unusually large, broadly ovate leaves covered in dense white woolly hairs — reminiscent of the leaves of orache (Atriplex) — which give the whole plant a striking silvery-grey appearance. Its pure bright yellow, unblotched flowers appear in late spring and early summer. Like all Halimium, it requires full sun and very free-draining soil and is adapted to hot, dry conditions; it is among the more tender species in the genus. No confirmed ASPCA pet-safety data exists; it is conservatively classified as mildly-toxic.

Cold limit: USDA 9-10 · RHS H3 (-5 to 40 °C)

Watch for — Frost and cold-wind damage: This is one of the more frost-tender Halimium species; temperatures below -5 °C (23 °F) or cold, drying winds can kill stems back significantly. In marginal climates grow against a warm, sheltered south-facing wall and mulch the root zone before winter.

What orache-leaved sun rose's hardiness rating actually means

Orache-Leaved Sun Rose is half-hardy (RHS H3). 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 H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 9-10 — 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 −5 to 1 °C — a light, short frost only. Orache-Leaved Sun Rose shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for orache-leaved sun rose as it gets too cold:

Down to roughly about −5 to 1 °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 orache-leaved sun rose go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-10 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 orache-leaved sun rose can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline orache-leaved sun rose

Orache-Leaved Sun 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.

Orache-Leaved Sun Rose hardiness — frequently asked questions

Is orache-leaved sun rose cold hardy?

Orache-Leaved Sun Rose is half-hardy (RHS H3). 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 9-10 (and sheltered UK gardens) orache-leaved sun 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 orache-leaved sun rose can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Orache-Leaved Sun Rose shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is orache-leaved sun rose?

Orache-Leaved Sun Rose is rated USDA 9-10 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can orache-leaved sun rose survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-10 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 orache-leaved sun 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.