Cold hardiness & minimum temperature

Is Nematanthus wettsteinii (Nematanthus wettsteinii)cold hardy? Hardiness zone & min temp

Also called miniature goldfish plant, Wettstein's nematanthus.

More about nematanthus wettsteinii

About Nematanthus wettsteinii

Nematanthus wettsteinii · also called miniature goldfish plant, Wettstein's nematanthus · flowering

Nematanthus wettsteinii is the classic miniature goldfish plant, a Brazilian gesneriad with small, thick, glossy dark-green leaves on slender trailing stems and abundant pouched orange-and-yellow flowers shaped like tiny goldfish. Easy and long-flowering, it thrives in a bright window or basket with warmth, a free-draining mix, and watering once the surface dries.

Cold limit: USDA 10-11 (grown indoors in most US homes) · RHS H1b (16-27°C)

Watch for — Bud and flower drop: Often from inconsistent watering, draughts, temperature swings, or very dry air. Keep conditions even and avoid moving the plant while in bud.

What nematanthus wettsteinii's hardiness rating actually means

Nematanthus wettsteinii 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 10-11 (grown indoors in most US homes) — 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 10 °C (sustained cold below this is damaging). Nematanthus wettsteinii has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for nematanthus wettsteinii as it gets too cold:

Below about about 10 °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 nematanthus wettsteinii go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °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 nematanthus wettsteinii can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Nematanthus wettsteinii hardiness — frequently asked questions

Is nematanthus wettsteinii cold hardy?

Nematanthus wettsteinii 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. Nematanthus wettsteinii can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (grown indoors in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature nematanthus wettsteinii can survive?

What hardiness zone is nematanthus wettsteinii?

Nematanthus wettsteinii is rated USDA 10-11 (grown indoors in most US homes) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can nematanthus wettsteinii survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °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 nematanthus wettsteinii below its minimum temperature?

Below about about 10 °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.