Cold hardiness & minimum temperature

Is Horsfield's Sauromatum (Sauromatum horsfieldii)cold hardy? Hardiness zone & min temp

Also called Horsfield's Voodoo Lily, Horsfield's Monarch-of-the-East.

More about horsfield's sauromatum

About Horsfield's Sauromatum

Sauromatum horsfieldii · also called Horsfield's Voodoo Lily, Horsfield's Monarch-of-the-East · tropical

Sauromatum horsfieldii is a tuberous aroid from Southeast Asia related to the better-known Voodoo Lily (S. venosum). It produces a spathe inflorescence followed by large, deeply divided compound leaves. Like all Sauromatum species, its inflorescence emits an unpleasant odour to attract pollinators. Toxic to pets as an aroid with calcium oxalates.

Cold limit: USDA 8–11 (tubers may survive mild winters outdoors in zone 8 with deep mulch) · RHS H3 (15–28°C)

Watch for — Tuber rot: Storing tubers in damp or cold conditions over winter causes rot. Lift tubers after foliage dies back, dry them thoroughly, and store in dry compost or paper bags at 10–15°C.

What horsfield's sauromatum's hardiness rating actually means

Horsfield's Sauromatum 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 (tubers may survive mild winters outdoors in zone 8 with deep mulch) — 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. Horsfield's Sauromatum shrugs off cold nights but a real, sustained freeze will kill it.

Concretely, for horsfield's sauromatum 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 horsfield's sauromatum go outside or overwinter — and where?

It can live outside year-round only in the mildest, most sheltered part of USDA 8–11 (tubers may survive mild winters outdoors in zone 8 with deep mulch) 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 horsfield's sauromatum 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 horsfield's sauromatum

Horsfield's Sauromatum 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.

Horsfield's Sauromatum hardiness — frequently asked questions

Is horsfield's sauromatum cold hardy?

Horsfield's Sauromatum 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 (tubers may survive mild winters outdoors in zone 8 with deep mulch) (and sheltered UK gardens) horsfield's sauromatum can stay out; in colder areas it must be lifted, brought in, or treated as a frost-tender plant.

What is the minimum temperature horsfield's sauromatum can survive?

Minimum survivable temperature is roughly about −5 to 1 °C — a light, short frost only. Horsfield's Sauromatum shrugs off cold nights but a real, sustained freeze will kill it.

What hardiness zone is horsfield's sauromatum?

Horsfield's Sauromatum is rated USDA 8–11 (tubers may survive mild winters outdoors in zone 8 with deep mulch) and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can horsfield's sauromatum survive winter outside?

It can live outside year-round only in the mildest, most sheltered part of USDA 8–11 (tubers may survive mild winters outdoors in zone 8 with deep mulch) 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 horsfield's sauromatum 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.