Cold hardiness & minimum temperature

Is Showy Sinningia (Sinningia conspicua)cold hardy? Hardiness zone & min temp

Also called Showy Sinningia, Conspicuous Sinningia, Brazilian Foxglove.

More about showy sinningia

About Showy Sinningia

Sinningia conspicua · also called Showy Sinningia, Conspicuous Sinningia · flowering

Sinningia conspicua is a tuberous perennial native to Brazil, forming compact rosettes of soft, velvety, mid-green hairy leaves from which it produces upright spikes of large pale-to-mid-yellow tubular flowers with cinnamon or purple internal markings from early summer through to autumn. Its foxglove-like flowers have a subtle lemon fragrance and are comparatively easy to grow under glass or as a houseplant in bright filtered light. After flowering, allow the foliage to die back naturally and keep the tuber dry over winter. The ASPCA lists Sinningia (Gloxinia) as non-toxic to cats and dogs.

Cold limit: USDA 10-11 (indoor in most climates) · RHS H1b (15–25°C)

Watch for — Vine weevil grubs attacking tubers: White grubs of the vine weevil (Otiorhynchus sulcatus) can hollow out tubers over winter; apply a biological nematode drench (Steinernema kraussei) in late summer or early autumn as a preventive measure.

What showy sinningia's hardiness rating actually means

Showy Sinningia 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 10-11 (indoor in most climates) — 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). Showy Sinningia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Showy Sinningia hardiness — frequently asked questions

Is showy sinningia cold hardy?

Showy Sinningia 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. Showy Sinningia can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature showy sinningia can survive?

What hardiness zone is showy sinningia?

Showy Sinningia is rated USDA 10-11 (indoor in most climates) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can showy sinningia 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 showy sinningia 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.