Cold hardiness & minimum temperature

Is Starfruit (Averrhoa carambola)cold hardy? Hardiness zone & min temp

Also called Starfruit, Carambola, Star apple.

More about starfruit

About Starfruit

Averrhoa carambola · also called Starfruit, Carambola · tropical

Starfruit, or carambola, is an attractive evergreen tropical tree from Southeast Asia bearing waxy, ribbed fruit that form five-pointed stars when sliced. It fruits young, sometimes year-round in the tropics, and adapts to containers. The whole tree, including fruit, contains oxalates and the neurotoxin caramboxin, making it hazardous to pets and people with kidney problems.

Cold limit: USDA 10-11 (frost-tender; mature trees take only brief, light cold) · RHS H1b (20-32°C)

Watch for — Cold sensitivity: Temperatures near or below freezing damage leaves, fruit and young branches; protect or shelter plants when cold threatens.

What starfruit's hardiness rating actually means

Starfruit 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 10-11 (frost-tender; mature trees take only brief, light cold) — 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). Starfruit has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Starfruit hardiness — frequently asked questions

Is starfruit cold hardy?

Starfruit 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. Starfruit can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (frost-tender; mature trees take only brief, light cold)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature starfruit can survive?

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

What hardiness zone is starfruit?

Starfruit is rated USDA 10-11 (frost-tender; mature trees take only brief, light cold) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can starfruit 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 starfruit 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.