Cold hardiness & minimum temperature

Is Large-Flowered Kohleria (Kohleria grandiflora)cold hardy? Hardiness zone & min temp

Also called Large-Flowered Kohleria, Kohleria.

More about large-flowered kohleria

About Large-Flowered Kohleria

Kohleria grandiflora · also called Large-Flowered Kohleria, Kohleria · flowering

A velvety-leaved Gesneriaceae from Colombia and Ecuador, Kohleria grandiflora produces tubular red flowers with yellow-spotted throats from spring through autumn. Grow it in bright indirect light with high humidity and consistently moist, well-drained soil. Rhizomes allow short dry spells but dislike cold. Near year-round blooms are possible under grow lights.

Cold limit: USDA 10a–11b · RHS H1b (18–24°C (active growth); above 16°C minimum)

Watch for — Rhizome rot: Overwatering in winter or heavy, poorly draining compost causes rhizomes to rot. Reduce water sharply after stems die back and ensure the pot drains freely.

What large-flowered kohleria's hardiness rating actually means

Large-Flowered Kohleria 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 10a–11b — 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). Large-Flowered Kohleria has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Large-Flowered Kohleria hardiness — frequently asked questions

Is large-flowered kohleria cold hardy?

Large-Flowered Kohleria 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. Large-Flowered Kohleria can only live outside year-round in genuinely frost-free climates (roughly USDA 10a–11b); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature large-flowered kohleria can survive?

What hardiness zone is large-flowered kohleria?

Large-Flowered Kohleria is rated USDA 10a–11b and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can large-flowered kohleria 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 large-flowered kohleria 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.