Cold hardiness & minimum temperature

Is Douglas's Sinningia (Sinningia douglasii)cold hardy? Hardiness zone & min temp

Also called Douglas's Sinningia, Douglas Sinningia.

More about douglas's sinningia

About Douglas's Sinningia

Sinningia douglasii · also called Douglas's Sinningia, Douglas Sinningia · flowering

Sinningia douglasii is a tuberous perennial native to humid rocky slopes and epiphytic habitats in southern Brazil and northern Argentina, growing naturally from lowland elevations up to about 800 m. It produces oval to lance-shaped, felty dark-green leaves and pink tubular flowers with prominent purple streaks on the inner lower lobes, attracting hummingbirds as its primary pollinators. Best grown in bright indirect light with free-draining compost, it benefits from a winter rest period after flowering, though this is less pronounced than in many other species. The ASPCA lists Sinningia (Gloxinia) as non-toxic to cats and dogs.

Cold limit: USDA 10-12 (indoor in most climates) · RHS H1b (18–24°C)

What douglas's sinningia's hardiness rating actually means

Douglas's 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 10-12 (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). Douglas's Sinningia has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Douglas's Sinningia hardiness — frequently asked questions

Is douglas's sinningia cold hardy?

Douglas's 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. Douglas's Sinningia can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (indoor in most climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature douglas's sinningia can survive?

What hardiness zone is douglas's sinningia?

Douglas's Sinningia is rated USDA 10-12 (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 douglas's 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 douglas's 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.