Cold hardiness & minimum temperature

Is Arisaema speciosum (Arisaema speciosum)cold hardy? Hardiness zone & min temp

Also called spectacular cobra lily, Himalayan jack-in-the-pulpit.

More about arisaema speciosum

About Arisaema speciosum

Arisaema speciosum · also called spectacular cobra lily, Himalayan jack-in-the-pulpit · flowering

Arisaema speciosum is a spectacular Eastern-Himalayan cobra lily with a single large three-parted leaf, often red-margined, atop a marbled stem, and a deep maroon-and-white striped spathe with a remarkably long, thread-like spadix tail. It grows in cool, frost-touched forests and wants humus-rich, moist, well-drained shade, dying back to a dormant tuber.

Cold limit: USDA 6-9 (hardy outdoor woodland perennial; resents summer heat) · RHS H5 (8-22°C)

Watch for — Tuber rot in dormancy: Wet winter soil rots the resting tuber. Ensure free drainage or lift and store cool and barely moist.

What arisaema speciosum's hardiness rating actually means

Yes — arisaema speciosum is genuinely cold hardy. Rated RHS H5 and USDA 6-9 (hardy outdoor woodland perennial; resents summer heat), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 6-9 (hardy outdoor woodland perennial; resents summer heat) — 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 −15 to −10 °C. Arisaema speciosum is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for arisaema speciosum as it gets too cold:

It tolerates winter lows to about −15 to −10 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can arisaema speciosum go outside or overwinter — and where?

Plant it out within USDA 6-9 (hardy outdoor woodland perennial; resents summer heat) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 arisaema speciosum can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Arisaema speciosum hardiness — frequently asked questions

Is arisaema speciosum cold hardy?

Yes — arisaema speciosum is genuinely cold hardy. Rated RHS H5 and USDA 6-9 (hardy outdoor woodland perennial; resents summer heat), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Arisaema speciosum is hardy across USDA 6-9 (hardy outdoor woodland perennial; resents summer heat); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature arisaema speciosum can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Arisaema speciosum is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is arisaema speciosum?

Arisaema speciosum is rated USDA 6-9 (hardy outdoor woodland perennial; resents summer heat) and RHS H5 — Hardy in most of the UK and in cold winters.

Can arisaema speciosum survive winter outside?

Plant it out within USDA 6-9 (hardy outdoor woodland perennial; resents summer heat) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to arisaema speciosum below its minimum temperature?

It tolerates winter lows to about −15 to −10 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.