Cold hardiness & minimum temperature

Is Naumann's Wax Plant (Hoya naumannii)cold hardy? Hardiness zone & min temp

Also called Naumann's wax plant, Naumann's hoya.

More about naumann's wax plant

About Naumann's Wax Plant

Hoya naumannii · also called Naumann's wax plant, Naumann's hoya · tropical

Hoya naumannii is a fast-growing epiphytic vine from Bougainville Island in the Solomon Islands, where it scrambles through tropical understory. It thrives in bright light with warm temperatures and rewards growers with clusters of flat, star-shaped white-and-pink flowers; provide a hoop or trellis from the outset as growth is vigorous even from a cutting. The single most important care fact is that it needs more light than most hoyas to initiate blooms — a bright east- or south-facing windowsill is ideal. The genus Hoya is listed as non-toxic to cats and dogs by the ASPCA.

Cold limit: USDA 11–12 (indoor in most climates) · RHS H1b (15–35 °C)

What naumann's wax plant's hardiness rating actually means

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

Concretely, for naumann's 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 naumann's 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 naumann's 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.

Naumann's Wax Plant hardiness — frequently asked questions

Is naumann's wax plant cold hardy?

Naumann's 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. Naumann's 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 naumann's wax plant can survive?

What hardiness zone is naumann's wax plant?

Naumann's 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 naumann's 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 naumann's 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.