Cold hardiness & minimum temperature

Is Macadamia (Macadamia integrifolia)cold hardy? Hardiness zone & min temp

Also called macadamia, smooth-shelled macadamia, Queensland nut.

More about macadamia

About Macadamia

Macadamia integrifolia · also called macadamia, smooth-shelled macadamia · edible

The smooth-shelled macadamia is a handsome subtropical evergreen yielding the world's richest dessert nut. Native to coastal Queensland rainforest, it wants warm, frost-free conditions, deep fertile acidic soil, and steady moisture. Trees are slow to bear (grafted plants in 4-6 years) but long-lived and productive, with glossy foliage and pendulous sprays of cream flowers.

Cold limit: USDA 9b-11 (outdoor; frost-tender) · RHS H1c (10 to 30°C)

Watch for — Frost and wind damage: Young trees are killed by frost and the brittle wood snaps in storms. Site in a sheltered, frost-free spot and stake until established.

What macadamia's hardiness rating actually means

Macadamia 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 9b-11 (outdoor; frost-tender) — 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). Macadamia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Macadamia hardiness — frequently asked questions

Is macadamia cold hardy?

Macadamia 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. Macadamia can only live outside year-round in genuinely frost-free climates (roughly USDA 9b-11 (outdoor; frost-tender)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature macadamia can survive?

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

What hardiness zone is macadamia?

Macadamia is rated USDA 9b-11 (outdoor; frost-tender) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can macadamia 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 macadamia 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.