Cold hardiness & minimum temperature

Is Crown Wax Plant (Hoya coronaria)cold hardy? Hardiness zone & min temp

Also called Crown wax plant, Wax plant.

More about crown wax plant

About Crown Wax Plant

Hoya coronaria · also called Crown wax plant, Wax plant · tropical

Hoya coronaria is an evergreen epiphytic climber native to lowland forests and mangrove swamps of Thailand, Malaysia, Indonesia, and the Philippines, recognised by its large, distinctive hairy (pubescent) leaves with a greenish-blue cast. It produces impressive, long-lasting, fragrant star-shaped flowers that begin lime-green and open to white. As a lowland tropical species it needs consistent warmth and high humidity, and is more cold-sensitive than many Hoyas; temperatures below 15 °C will damage it. 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 (18–30 °C)

Watch for — Cold damage and leaf drop: Temperatures below 15 °C cause leaf yellowing, drop, and growth arrest; keep away from draughty windows or cold windowsills in winter, especially in the UK.

What crown wax plant's hardiness rating actually means

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

Concretely, for crown 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 crown 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 crown 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.

Crown Wax Plant hardiness — frequently asked questions

Is crown wax plant cold hardy?

Crown 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. Crown 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 crown wax plant can survive?

What hardiness zone is crown wax plant?

Crown 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 crown 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 crown 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.