Cold hardiness & minimum temperature

Is Poisson's Nephthytis (Nephthytis poissonii)cold hardy? Hardiness zone & min temp

Also called Poisson Nephthytis, Tropical Forest Aroid.

More about poisson's nephthytis

About Poisson's Nephthytis

Nephthytis poissonii · also called Poisson Nephthytis, Tropical Forest Aroid · tropical

Nephthytis poissonii is a rare tropical aroid from West and Central African forests, similar in habit to N. afzelii but distinct in leaf shape and spadix structure. Grown primarily as a botanical curiosity in specialist collections. Like all true Nephthytis, it contains calcium oxalate crystals and is toxic to pets and people if ingested.

Cold limit: USDA 11-12 (indoor-only) · RHS H1a (18-28°C)

Watch for — No new growth: Often a winter rest response or pot-bound roots; repot in spring into a slightly larger container.

What poisson's nephthytis's hardiness rating actually means

Poisson's Nephthytis is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Its RHS rating of H1a means: Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever. On the US scale that maps to USDA 11-12 (indoor-only) — 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 above about 15 °C (warm, never cold). Poisson's Nephthytis has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for poisson's nephthytis as it gets too cold:

Below about above about 15 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches.
A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover.
Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.

Can poisson's nephthytis go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above above 15 °C, in shade or dappled light, hardened off gradually.
Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C.
It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

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 poisson's nephthytis can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Poisson's Nephthytis hardiness — frequently asked questions

Is poisson's nephthytis cold hardy?

Poisson's Nephthytis is not cold hardy. It is a tropical houseplant that dies if it is left out through frost — there is no zone where it overwinters outdoors in a UK or cold-US climate. Indoor-only in almost every home. Poisson's Nephthytis can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (indoor-only)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature poisson's nephthytis can survive?

Minimum survivable temperature is roughly above about 15 °C (warm, never cold). Poisson's Nephthytis has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is poisson's nephthytis?

Poisson's Nephthytis is rated USDA 11-12 (indoor-only) and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can poisson's nephthytis survive winter outside?

It can holiday outdoors in summer once nights are reliably above above 15 °C, in shade or dappled light, hardened off gradually. Bring it back indoors well before the first autumn frost — do not wait for a frost warning, move it when nights drop toward 10-12 °C. It will never overwinter outside in a temperate climate; the indoors is its winter home, full stop.

What happens to poisson's nephthytis below its minimum temperature?

Below about above about 15 °C, growth stalls and the leaves start to show cold stress — dark, water-soaked, or yellowing patches. A single light frost blackens the foliage; a hard freeze kills the whole plant, roots included, and it does not recover. Even a cold, draughty windowsill or an unheated porch in winter can be enough to damage it permanently.