Cold hardiness & minimum temperature

Is Hairy Kohleria (Kohleria hirsuta)cold hardy? Hardiness zone & min temp

Also called Hairy Kohleria, Hirsute Kohleria.

More about hairy kohleria

About Hairy Kohleria

Kohleria hirsuta · also called Hairy Kohleria, Hirsute Kohleria · houseplant

Kohleria hirsuta is a softly hairy gesneriad from South America, producing erect, velvety stems covered in dense white trichomes and pendulous, tubular red-orange flowers spotted inside. Growing from scaly rhizomes, it can be rested in winter and revived in spring. An excellent houseplant for warm rooms with bright indirect light and moderate humidity.

Cold limit: USDA 10–12 · RHS H1b (18–26°C)

Watch for — Rhizome rot: Overwatering during the growing season or keeping rhizomes too wet during dormancy causes rot. Let the soil dry more between waterings and store dormant rhizomes in slightly moist (not wet) perlite or compost over winter.

What hairy kohleria's hardiness rating actually means

Hairy 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 10–12 — 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). Hairy Kohleria has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Hairy Kohleria hardiness — frequently asked questions

Is hairy kohleria cold hardy?

Hairy 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. Hairy Kohleria can only live outside year-round in genuinely frost-free climates (roughly USDA 10–12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature hairy kohleria can survive?

What hardiness zone is hairy kohleria?

Hairy Kohleria is rated USDA 10–12 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can hairy 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 hairy 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.