Cold hardiness & minimum temperature

Is Long-leaved Pelargonium (Pelargonium longifolium)cold hardy? Hardiness zone & min temp

Also called Long-leaved Pelargonium, Long-leaf Geranium.

More about long-leaved pelargonium

About Long-leaved Pelargonium

Pelargonium longifolium · also called Long-leaved Pelargonium, Long-leaf Geranium · flowering

Pelargonium longifolium is a tuberous geophyte native to the arid and semi-arid zones of South Africa's Western Cape, producing narrow, strap-shaped leaves and pale cream to yellowish flowers marked with dark purple veins. As a summer-dormant bulb-like plant it follows a Mediterranean rhythm — grow in autumn and winter, rest in summer — and demands excellent drainage and minimal water during dormancy. The single most important care fact is to withhold almost all water in summer when the plant is leafless, or the tuber will rot. Toxic to cats, dogs, and horses.

Cold limit: USDA 9-11 (overwinter frost-free elsewhere) · RHS H2 (7–24°C)

What long-leaved pelargonium's hardiness rating actually means

Long-leaved Pelargonium 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 (overwinter frost-free elsewhere) — 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. Long-leaved Pelargonium shrugs off cold nights but a real, sustained freeze will kill it.

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

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (overwinter frost-free elsewhere) 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 long-leaved pelargonium 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 long-leaved pelargonium

Long-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.

Long-leaved Pelargonium hardiness — frequently asked questions

Is long-leaved pelargonium cold hardy?

Long-leaved Pelargonium 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 (overwinter frost-free elsewhere) (and sheltered UK gardens) long-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 long-leaved pelargonium can survive?

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

What hardiness zone is long-leaved pelargonium?

Long-leaved Pelargonium is rated USDA 9-11 (overwinter frost-free elsewhere) and RHS H2 — Tender — survives a frost-free greenhouse or a very mild, sheltered spot.

Can long-leaved pelargonium survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 9-11 (overwinter frost-free elsewhere) 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 long-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.