Cold hardiness & minimum temperature

Is Portella Ruellia (Ruellia portellae)cold hardy? Hardiness zone & min temp

Also called Portella Ruellia, Monkey Plant.

More about portella ruellia

About Portella Ruellia

Ruellia portellae · also called Portella Ruellia, Monkey Plant · tropical

An evergreen tropical perennial from Brazil valued as a spreading ground cover with ornamental foliage — dark green leaves etched with white veins and vivid red undersides — and delicate pale pink tubular flowers produced at the leaf axils. Best grown as a warm houseplant or in frost-free gardens where it makes excellent low foliage cover.

Cold limit: USDA 10-12 · RHS H1b (18–22°C (min. 15°C))

Watch for — Leaf discolouration from cold or draughts: This tropical species is sensitive to cold air, draughts, and temperatures below 15°C. Chilling causes darkening, puckering, or dropping of leaves. Keep away from draughty windows and cold windowsills in winter.

What portella ruellia's hardiness rating actually means

Portella Ruellia 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). Portella Ruellia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Portella Ruellia hardiness — frequently asked questions

Is portella ruellia cold hardy?

Portella Ruellia 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. Portella Ruellia 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 portella ruellia can survive?

What hardiness zone is portella ruellia?

Portella Ruellia 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 portella ruellia 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 portella ruellia 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.