Cold hardiness & minimum temperature

Is Jungle Geranium (Ixora coccinea)cold hardy? Hardiness zone & min temp

Also called Jungle geranium, Flame of the woods, Jungle flame, Iron tree, Maui sunset, Ixora.

More about jungle geranium

About Jungle Geranium

Ixora coccinea · also called Jungle geranium, Flame of the woods · flowering

Jungle geranium (Ixora coccinea) is a tropical evergreen shrub from the coffee family, grown for near-continuous globular clusters of red, orange, pink, or yellow tubular flowers. It demands full sun, acidic soil, warmth, and humidity. The ASPCA lists it as non-toxic to dogs, cats, and horses, making it pet-safe.

Cold limit: USDA 9b-11 (best in 10-11; root-hardy in 9b where top growth may die back in frost) (18-29°C)

Watch for — Few or no flowers: Almost always insufficient light. Move to full sun or the brightest window. Cold drafts, overpruning at the wrong time, or letting the soil dry out can also cause bud drop.

What jungle geranium's hardiness rating actually means

Jungle Geranium 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 9b-11 (best in 10-11; root-hardy in 9b where top growth may die back in frost) — 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). Jungle Geranium has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for jungle geranium 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 jungle geranium 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 jungle geranium can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Jungle Geranium hardiness — frequently asked questions

Is jungle geranium cold hardy?

Jungle Geranium 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. Jungle Geranium can only live outside year-round in genuinely frost-free climates (roughly USDA 9b-11 (best in 10-11; root-hardy in 9b where top growth may die back in frost)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature jungle geranium can survive?

What hardiness zone is jungle geranium?

Jungle Geranium is rated USDA 9b-11 (best in 10-11; root-hardy in 9b where top growth may die back in frost) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can jungle geranium 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 jungle geranium 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.