Cold hardiness & minimum temperature

Is Green-flowered Wax Plant (Hoya chlorantha)cold hardy? Hardiness zone & min temp

Also called Green-flowered wax plant, Wax plant.

More about green-flowered wax plant

About Green-flowered Wax Plant

Hoya chlorantha · also called Green-flowered wax plant, Wax plant · tropical

Hoya chlorantha is a twining epiphytic vine native to Samoa, distinguished by its thin, smooth, grassy-green leaves on notably curly stems and its unusual light green star-shaped flowers with a yellow-green corona that produce abundant nectar. Two colour forms exist, including a lilac-red variant. It prefers warm, humid conditions with bright indirect light and well-drained growing medium, and its curly stems make it an unusual display plant even out of flower. The ASPCA classifies the Hoya genus as non-toxic to cats, dogs, and horses.

Cold limit: USDA 11–12 (indoor in most climates) · RHS H1b (16–29 °C)

What green-flowered wax plant's hardiness rating actually means

Green-flowered Wax Plant 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 11–12 (indoor in most climates) — 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). Green-flowered Wax Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for green-flowered wax plant 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 green-flowered wax plant 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 green-flowered wax plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Green-flowered Wax Plant hardiness — frequently asked questions

Is green-flowered wax plant cold hardy?

Green-flowered Wax Plant 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. Green-flowered Wax Plant can only live outside year-round in genuinely frost-free climates (roughly USDA 11–12 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature green-flowered wax plant can survive?

What hardiness zone is green-flowered wax plant?

Green-flowered Wax Plant is rated USDA 11–12 (indoor in most climates) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can green-flowered wax plant 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 green-flowered wax plant 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.