Cold hardiness & minimum temperature

Is Nummularioides Wax Plant (Hoya nummularioides)cold hardy? Hardiness zone & min temp

Also called Nummularioides Wax Plant, Coin-leaf Hoya, Wax Plant, Wax Flower.

More about nummularioides wax plant

About Nummularioides Wax Plant

Hoya nummularioides · also called Nummularioides Wax Plant, Coin-leaf Hoya · flowering

Hoya nummularioides is a compact, twining epiphytic vine from mainland Southeast Asia, grown for fuzzy coin-shaped leaves and fragrant white-and-pink star flowers. Give it bright indirect light, a chunky free-draining mix, and let it nearly dry between waterings. The ASPCA classifies the Hoya genus as pet-safe.

Cold limit: USDA 10-12 (18-29C)

Watch for — Bud drop: Flower buds can abort if the plant is moved, rotated, or hit by drafts and big temperature swings once buds have set. Leave it in place and keep conditions stable until the flowers open, and never cut off the old flower spurs (peduncles).

What nummularioides wax plant's hardiness rating actually means

Nummularioides 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-12 — 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 5 °C (and never frost). Nummularioides Wax Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for nummularioides wax plant as it gets too cold:

Below about about 5 °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 nummularioides wax plant go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °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 nummularioides wax plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Nummularioides Wax Plant hardiness — frequently asked questions

Is nummularioides wax plant cold hardy?

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

What is the minimum temperature nummularioides wax plant can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Nummularioides Wax Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is nummularioides wax plant?

Nummularioides Wax Plant is rated USDA 10-12 and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can nummularioides wax plant survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 nummularioides wax plant below its minimum temperature?

Below about about 5 °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.