Cold hardiness & minimum temperature

Is Kaffir Lime (Citrus hystrix)cold hardy? Hardiness zone & min temp

Also called kaffir lime, makrut lime, Thai lime.

More about kaffir lime

About Kaffir Lime

Citrus hystrix · also called kaffir lime, makrut lime · herb

Makrut lime is a small, thorny citrus tree grown chiefly for its intensely aromatic, double-lobed leaves, an essential flavouring in Thai, Cambodian, and Indonesian cooking, and for its bumpy, fragrant fruit zest. Tender and frost-sensitive, it is widely grown in containers and brought indoors over winter in cool climates, rewarding warmth, bright light, and steady moisture.

Cold limit: USDA 9-11 (frost-tender; grown indoors or under glass in cooler zones) · RHS H1c (15-30°C)

Watch for — Leaf drop from cold or overwatering: Sudden chills, drafts, or soggy roots cause leaves to yellow and drop. Keep above 10°C, away from cold windows and heaters, and let the soil surface dry between waterings.

What kaffir lime's hardiness rating actually means

Kaffir Lime 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 (frost-tender; grown indoors or under glass in cooler zones) — 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). Kaffir Lime has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Kaffir Lime hardiness — frequently asked questions

Is kaffir lime cold hardy?

Kaffir Lime 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. Kaffir Lime can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (frost-tender; grown indoors or under glass in cooler zones)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature kaffir lime can survive?

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

What hardiness zone is kaffir lime?

Kaffir Lime is rated USDA 9-11 (frost-tender; grown indoors or under glass in cooler zones) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can kaffir lime 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 kaffir lime 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.