Cold hardiness & minimum temperature

Is Hoya Sarawakensis (Hoya sarawakensis)cold hardy? Hardiness zone & min temp

Also called Sarawak hoya, Borneo wax vine.

More about hoya sarawakensis

About Hoya Sarawakensis

Hoya sarawakensis · also called Sarawak hoya, Borneo wax vine · houseplant

Hoya sarawakensis is a striking large-leaved epiphyte from Sarawak on Borneo, with thick, glossy foliage and showy ball-shaped umbels of fuzzy reddish-brown to orange flowers. A warmth-loving climber, it grows as an epiphyte in humid lowland forest and adapts to indoor culture given bright indirect light, a chunky mix and steady warmth.

Cold limit: USDA 11-12 (indoor in most US homes) · RHS H1b (20-30°C)

Watch for — Cold or draught damage: This warmth-loving Bornean species sulks below about 16°C, dropping or browning leaves. Keep it warm and away from cold windows and air-conditioning drafts.

What hoya sarawakensis's hardiness rating actually means

Hoya Sarawakensis 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 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). Hoya Sarawakensis has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for hoya sarawakensis 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 hoya sarawakensis 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 hoya sarawakensis can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Hoya Sarawakensis hardiness — frequently asked questions

Is hoya sarawakensis cold hardy?

Hoya Sarawakensis 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. Hoya Sarawakensis can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (indoor in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature hoya sarawakensis can survive?

What hardiness zone is hoya sarawakensis?

Hoya Sarawakensis is rated USDA 11-12 (indoor 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 hoya sarawakensis 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 hoya sarawakensis 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.