Cold hardiness & minimum temperature

Is Pseuderanthemum carruthersii var. carruthersii (Pseuderanthemum carruthersii var. carruthersii)cold hardy? Hardiness zone & min temp

Also called Yellow-splashed pseuderanthemum.

More about pseuderanthemum carruthersii var. carruthersii

About Pseuderanthemum carruthersii var. carruthersii

Pseuderanthemum carruthersii var. carruthersii · also called Yellow-splashed pseuderanthemum · tropical

Pseuderanthemum carruthersii var. carruthersii is a tender tropical shrub prized for foliage splashed and mottled with golden-yellow over green. Native to the Pacific Islands, it wants warmth, high humidity, and bright filtered light to keep its variegation vivid. Grown as a colourful houseplant or, in frost-free regions, a compact ornamental hedge.

Cold limit: USDA 10-12 (indoor elsewhere; outdoors only where frost-free) · RHS H1b (18-29°C)

Watch for — Browning leaf margins: A symptom of low humidity or dry, heated air. Boost ambient humidity and keep the plant away from radiators and cold drafts.

What pseuderanthemum carruthersii var. carruthersii's hardiness rating actually means

Pseuderanthemum carruthersii var. carruthersii 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 (indoor elsewhere; outdoors only where frost-free) — 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). Pseuderanthemum carruthersii var. carruthersii has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Pseuderanthemum carruthersii var. carruthersii hardiness — frequently asked questions

Is pseuderanthemum carruthersii var. carruthersii cold hardy?

Pseuderanthemum carruthersii var. carruthersii 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. Pseuderanthemum carruthersii var. carruthersii can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor elsewhere; outdoors only where frost-free)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature pseuderanthemum carruthersii var. carruthersii can survive?

What hardiness zone is pseuderanthemum carruthersii var. carruthersii?

Pseuderanthemum carruthersii var. carruthersii is rated USDA 10-12 (indoor elsewhere; outdoors only where frost-free) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can pseuderanthemum carruthersii var. carruthersii 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 pseuderanthemum carruthersii var. carruthersii 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.