Cold hardiness & minimum temperature

Is Natal Plum Bonsai (Carissa macrocarpa)cold hardy? Hardiness zone & min temp

Also called Natal Plum Bonsai, Large Num-Num.

More about natal plum bonsai

About Natal Plum Bonsai

Carissa macrocarpa · also called Natal Plum Bonsai, Large Num-Num · tropical

Natal plum bonsai is a thorny South African evergreen prized for glossy leaves, fragrant white star flowers, and edible red fruit. As a subtropical species it wants strong light, even moisture, and frost-free warmth. Its spiny branches and dense, woody growth take well to wiring and clip-and-grow shaping into compact, fruiting specimens.

Cold limit: USDA 9-11 (indoor/greenhouse bonsai in most US homes) · RHS H1c (16-29°C)

Watch for — Leaf drop and yellowing: Usually from overwatering and soggy roots, sudden cold drafts, or moving the plant. Let soil dry between waterings and keep it warm and stable.

What natal plum bonsai's hardiness rating actually means

Natal Plum Bonsai 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 9-11 (indoor/greenhouse bonsai in most US homes) — 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). Natal Plum Bonsai has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for natal plum bonsai 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 natal plum bonsai 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 natal plum bonsai can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Natal Plum Bonsai hardiness — frequently asked questions

Is natal plum bonsai cold hardy?

Natal Plum Bonsai 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. Natal Plum Bonsai can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor/greenhouse bonsai in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature natal plum bonsai can survive?

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

What hardiness zone is natal plum bonsai?

Natal Plum Bonsai is rated USDA 9-11 (indoor/greenhouse bonsai in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can natal plum bonsai 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 natal plum bonsai 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.