Cold hardiness & minimum temperature

Is Southernwood-leaved Pelargonium (Pelargonium abrotanifolium)cold hardy? Hardiness zone & min temp

Also called Southernwood-leaved Pelargonium, Camphor Pelargonium, Wormwood-leaved Geranium.

More about southernwood-leaved pelargonium

About Southernwood-leaved Pelargonium

Pelargonium abrotanifolium · also called Southernwood-leaved Pelargonium, Camphor Pelargonium · herb

Pelargonium abrotanifolium is a compact, shrubby scented-leaf species from the dry rocky hillsides of South Africa's Western and Eastern Cape, named for its feathery, deeply divided leaves that closely resemble those of southernwood (Artemisia abrotanum) and carry a fresh, camphor-like fragrance. Small white to pale pink flowers with dark-purple veining appear through spring and summer. Hardy to a light frost once established but best treated as a conservatory or frost-free patio plant in the UK; it is one of the more drought-tolerant pelargoniums and must have sharply draining soil. Toxic to cats and dogs.

Cold limit: USDA 8-11 (borderline hardy in a sheltered, dry spot; protect below -3°C) · RHS H3 (5-30°C)

Watch for — Root rot in wet compost: The most common cause of failure in UK gardens; this dry-scrub native rots quickly in moisture-retentive soil or during wet winters. Grow in very gritty compost, pot in terracotta, and bring under cover before persistent autumn rain begins.

What southernwood-leaved pelargonium's hardiness rating actually means

Southernwood-leaved Pelargonium 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 8-11 (borderline hardy in a sheltered, dry spot; protect below -3°C) — 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. Southernwood-leaved Pelargonium shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for southernwood-leaved pelargonium 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 southernwood-leaved pelargonium go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 (borderline hardy in a sheltered, dry spot; protect below -3°C) 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 southernwood-leaved pelargonium 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 southernwood-leaved pelargonium

Southernwood-leaved Pelargonium 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.

Southernwood-leaved Pelargonium hardiness — frequently asked questions

Is southernwood-leaved pelargonium cold hardy?

Southernwood-leaved Pelargonium 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 8-11 (borderline hardy in a sheltered, dry spot; protect below -3°C) (and sheltered UK gardens) southernwood-leaved pelargonium can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature southernwood-leaved pelargonium can survive?

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

What hardiness zone is southernwood-leaved pelargonium?

Southernwood-leaved Pelargonium is rated USDA 8-11 (borderline hardy in a sheltered, dry spot; protect below -3°C) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can southernwood-leaved pelargonium survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8-11 (borderline hardy in a sheltered, dry spot; protect below -3°C) 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 southernwood-leaved pelargonium 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.