Cold hardiness & minimum temperature

Is Souari Nut (Caryocar nuciferum)cold hardy? Hardiness zone & min temp

Also called souari nut, butternuts of Guiana.

More about souari nut

About Souari Nut

Caryocar nuciferum · also called souari nut, butternuts of Guiana · edible

Souari nut is a giant evergreen rainforest tree from northern South America, grown for large oily kernels said to be sweeter than almonds. An emergent canopy species needing wet-tropical heat, deep fertile loam and high humidity, it is strictly glasshouse material outside the tropics and famously slow, often taking a decade or two to fruit.

Cold limit: USDA 11-12 (frost-tender; glasshouse-only in US/UK) · RHS H1a (21-30°C)

Watch for — Frost intolerance: Cannot tolerate frost; even brief cold is fatal, so it must be kept warm under glass in temperate regions.

What souari nut's hardiness rating actually means

Souari Nut 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 H1a means: Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever. On the US scale that maps to USDA 11-12 (frost-tender; glasshouse-only in US/UK) — 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 above about 15 °C (warm, never cold). Souari Nut has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for souari nut as it gets too cold:

Below about above about 15 °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 souari nut go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above above 15 °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 souari nut can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Souari Nut hardiness — frequently asked questions

Is souari nut cold hardy?

Souari Nut 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. Souari Nut can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (frost-tender; glasshouse-only in US/UK)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature souari nut can survive?

Minimum survivable temperature is roughly above about 15 °C (warm, never cold). Souari Nut has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is souari nut?

Souari Nut is rated USDA 11-12 (frost-tender; glasshouse-only in US/UK) and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can souari nut survive winter outside?

It can holiday outdoors in summer once nights are reliably above above 15 °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 souari nut below its minimum temperature?

Below about above about 15 °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.