Cold hardiness & minimum temperature

Is Lemongrass (Cymbopogon citratus)cold hardy? Hardiness zone & min temp

Also called West Indian lemongrass, sereh, fever grass.

About Lemongrass

Cymbopogon citratus · also called West Indian lemongrass, sereh · herb

Lemongrass is a tropical clumping grass from south Asia with intensely lemon-scented stems and leaves used in Thai and Vietnamese cooking. Tender; grown as an annual or overwintered as a houseplant in cool climates. Toxic to pets due to essential oils.

Lemongrass (Cymbopogon citratus, Poaceae) is a frost-tender clumping tropical grass widely grown in the tropics and subtropics for its lemony stalks used in Southeast Asian cooking; hardy only to about USDA zones 9-10.

Clumps grow slowly until summer heat and humidity arrive, then enlarge dramatically into dense clumps up to 6 ft wide; frost kills it, so harvest or dig and overwinter indoors before freezing.

Cold limit: USDA 9-11 (indoor or annual elsewhere) · RHS H1c (21-29°C)

Watch for — Frost damage: Tender — bring indoors or dig clump in autumn.

Sources: hort.extension.wisc.edu, plants.ces.ncsu.edu, missouribotanicalgarden.org

What lemongrass's hardiness rating actually means

Lemongrass 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 or annual elsewhere) — 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). Lemongrass has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Lemongrass hardiness — frequently asked questions

Is lemongrass cold hardy?

Lemongrass 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. Lemongrass can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor or annual elsewhere)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature lemongrass can survive?

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

What hardiness zone is lemongrass?

Lemongrass is rated USDA 9-11 (indoor or annual elsewhere) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can lemongrass 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 lemongrass 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.