Cold hardiness & minimum temperature

Is Citronella Grass (Cymbopogon nardus)cold hardy? Hardiness zone & min temp

Also called Citronella Grass, Nardus Grass, Sri Lanka Lemongrass.

More about citronella grass

About Citronella Grass

Cymbopogon nardus · also called Citronella Grass, Nardus Grass · herb

Citronella Grass is a large, clump-forming tropical grass native to South and Southeast Asia, grown commercially as the source of true citronella essential oil used in insect repellents and perfumery. It produces tall, graceful, blue-green arching leaves with a strong citrus-like scent when crushed. In temperate climates it is grown as a tender annual or container specimen.

Cold limit: USDA 10-12 · RHS H1b (15 to 40°C)

Watch for — Cold damage / frost kill: Cymbopogon nardus is a true tropical and will be killed to the ground — or to the roots — by frost. In USDA Zones 9 and below, bring container plants indoors before the first frost (typically when nights drop below 10°C). Overwinter in a bright, frost-free greenhouse or sunny room, keeping the soil barely moist.

What citronella grass's hardiness rating actually means

Citronella Grass 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 10-12 — 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 10 °C (sustained cold below this is damaging). Citronella Grass has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for citronella grass as it gets too cold:

Below about about 10 °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 citronella grass go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 10 °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 citronella grass can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Citronella Grass hardiness — frequently asked questions

Is citronella grass cold hardy?

Citronella Grass 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. Citronella Grass can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature citronella grass can survive?

What hardiness zone is citronella grass?

Citronella Grass is rated USDA 10-12 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can citronella grass survive winter outside?

It can holiday outdoors in summer once nights are reliably above 10 °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 citronella grass below its minimum temperature?

Below about about 10 °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.