Cold hardiness & minimum temperature

Is Jacobinia Carnea (Justicia carnea)cold hardy? Hardiness zone & min temp

Also called Brazilian plume flower, flamingo flower, jacobinia.

More about jacobinia carnea

About Jacobinia Carnea

Justicia carnea · also called Brazilian plume flower, flamingo flower · flowering

Justicia carnea is a soft-stemmed tropical shrub from Brazil grown for its large, plume-like heads of pink to rose flowers above deeply veined, dark green leaves. It flowers freely in warmth and bright indirect light, and stays bushy with regular pinching. Grown indoors or in a conservatory in temperate climates, outdoors in frost-free gardens.

Cold limit: USDA 9-11 (indoor/conservatory in most of the US and UK) · RHS H1b (16-27°C)

Watch for — Leaf drop from dry air or drought: Low humidity, draughts or a dried-out rootball trigger sudden leaf loss. Keep humidity up, avoid radiators and cold air, and never let the soft stems wilt fully.

What jacobinia carnea's hardiness rating actually means

Jacobinia Carnea 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 9-11 (indoor/conservatory in most of the US and UK) — 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). Jacobinia Carnea has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Jacobinia Carnea hardiness — frequently asked questions

Is jacobinia carnea cold hardy?

Jacobinia Carnea 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. Jacobinia Carnea can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor/conservatory in most of the US and UK)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature jacobinia carnea can survive?

What hardiness zone is jacobinia carnea?

Jacobinia Carnea is rated USDA 9-11 (indoor/conservatory in most of the US and UK) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can jacobinia carnea 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 jacobinia carnea 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.