Cold hardiness & minimum temperature

Is Hollow-Corolla Wax Plant (Hoya excavata)cold hardy? Hardiness zone & min temp

Also called Hollow-corolla wax plant, Excavated wax plant, Wax plant.

More about hollow-corolla wax plant

About Hollow-Corolla Wax Plant

Hoya excavata · also called Hollow-corolla wax plant, Excavated wax plant · tropical

Hoya excavata is a robust epiphytic vine notable for its distinctive flowers: soft yellow petals with bluish-white hairs near the base, and a fleshy, concave (hollow) corona coloured rich red or intense pink — the feature that gives it its name. Native to tropical Asia, it belongs to the Amblyostemma group, which is known for resilience and the ability to recover from extended dry periods of up to 20 days. Provide bright indirect light, an airy well-draining mix, and water sparingly. The ASPCA lists the Hoya genus as non-toxic to cats and dogs.

Cold limit: USDA 10–12 (indoor in most climates) · RHS H1b (16–30°C)

What hollow-corolla wax plant's hardiness rating actually means

Hollow-Corolla 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 10–12 (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). Hollow-Corolla Wax Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for hollow-corolla 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 hollow-corolla 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 hollow-corolla 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.

Hollow-Corolla Wax Plant hardiness — frequently asked questions

Is hollow-corolla wax plant cold hardy?

Hollow-Corolla 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. Hollow-Corolla Wax Plant can only live outside year-round in genuinely frost-free climates (roughly USDA 10–12 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature hollow-corolla wax plant can survive?

What hardiness zone is hollow-corolla wax plant?

Hollow-Corolla Wax Plant is rated USDA 10–12 (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 hollow-corolla 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 hollow-corolla 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.