Cold hardiness & minimum temperature

Is Bush Hoya (Hoya cumingiana)cold hardy? Hardiness zone & min temp

Also called Bush Hoya, Wax Plant, Cuming's Hoya.

More about bush hoya

About Bush Hoya

Hoya cumingiana · also called Bush Hoya, Wax Plant · houseplant

Bush Hoya is an upright, shrubby wax plant from Southeast Asia, prized for tightly stacked waxy leaves and spicy-scented, star-shaped flowers. Give it bright indirect light, let the top inch of soil dry between waterings, and keep it warm. It is considered pet-safe: the Hoya genus is ASPCA non-toxic.

Cold limit: USDA 11-12 (18-29°C)

Watch for — Cold or draft damage: Temperatures below about 15°C (59°F) and cold drafts damage foliage. Keep it warm and away from drafty windows, doors, and AC vents.

What bush hoya's hardiness rating actually means

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

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

Bush Hoya hardiness — frequently asked questions

Is bush hoya cold hardy?

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

What is the minimum temperature bush hoya can survive?

Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Bush Hoya has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is bush hoya?

Bush Hoya is rated USDA 11-12 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can bush hoya 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 bush hoya 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.