Cold hardiness & minimum temperature

Is Ancistrachne uncinulella (Ruellia tuberosa)cold hardy? Hardiness zone & min temp

Also called Minnie root, Feverroot.

More about ancistrachne uncinulella

About Ancistrachne uncinulella

Ruellia tuberosa · also called Minnie root, Feverroot · tropical

Ruellia tuberosa, called minnie root or feverroot, is a tropical Acanthaceae perennial with thick tuberous roots and funnel-shaped violet flowers. It thrives in bright sun, warm conditions, and well-drained sandy loam, tolerating dry spells once established. Native to Central America, it self-seeds freely via explosive seed capsules and naturalises easily in frost-free climates.

Cold limit: USDA 9-11 (root-hardy in zone 8b with mulch; grown as annual or pot plant elsewhere) · RHS H1c (18-32°C)

Watch for — Frost dieback: Top growth is cut down by frost. In borderline zones, mulch the roots heavily or lift and overwinter the tubers somewhere frost-free.

What ancistrachne uncinulella's hardiness rating actually means

Ancistrachne uncinulella 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 (root-hardy in zone 8b with mulch; grown as annual or pot plant 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). Ancistrachne uncinulella has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Ancistrachne uncinulella hardiness — frequently asked questions

Is ancistrachne uncinulella cold hardy?

Ancistrachne uncinulella 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. Ancistrachne uncinulella can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (root-hardy in zone 8b with mulch; grown as annual or pot plant elsewhere)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature ancistrachne uncinulella can survive?

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

What hardiness zone is ancistrachne uncinulella?

Ancistrachne uncinulella is rated USDA 9-11 (root-hardy in zone 8b with mulch; grown as annual or pot plant elsewhere) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can ancistrachne uncinulella 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 ancistrachne uncinulella 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.