Cold hardiness & minimum temperature

Is Obscura Wax Plant (Hoya obscura)cold hardy? Hardiness zone & min temp

Also called Obscura wax plant, Wax plant, Wax flower, Porcelain flower.

More about obscura wax plant

About Obscura Wax Plant

Hoya obscura · also called Obscura wax plant, Wax plant · houseplant

Hoya obscura is a compact, semi-succulent epiphytic vine from the Philippines, prized for veined leaves that flush coppery-red in bright light and fragrant clustered blooms. Give it bright indirect light, let the chunky mix dry between waterings, and keep it warm. ASPCA data indicates the genus is pet-safe, but verify with your vet.

Cold limit: USDA 10-12 (tender; grow as a houseplant or outdoors only in frost-free climates) (18-29 C)

Watch for — Leaf drop or shrivelling: Caused by watering extremes or cold stress. Keep temperatures above about 15 C (60 F), away from cold draughts, and maintain a steady wet-then-dry watering rhythm.

What obscura wax plant's hardiness rating actually means

Obscura 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-12 (tender; grow as a houseplant or outdoors only in frost-free 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 5 °C (and never frost). Obscura Wax Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for obscura wax plant as it gets too cold:

Below about about 5 °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 obscura wax plant go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °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 obscura wax plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Obscura Wax Plant hardiness — frequently asked questions

Is obscura wax plant cold hardy?

Obscura 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. Obscura Wax Plant can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (tender; grow as a houseplant or outdoors only in frost-free climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature obscura wax plant can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Obscura Wax Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is obscura wax plant?

Obscura Wax Plant is rated USDA 10-12 (tender; grow as a houseplant or outdoors only in frost-free climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can obscura wax plant survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 obscura wax plant below its minimum temperature?

Below about about 5 °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.