Cold hardiness & minimum temperature

Is Calanthe sylvatica (Calanthe sylvatica)cold hardy? Hardiness zone & min temp

Also called Forest Calanthe, African Calanthe.

More about calanthe sylvatica

About Calanthe sylvatica

Calanthe sylvatica · also called Forest Calanthe, African Calanthe · tropical

Calanthe sylvatica is an evergreen, terrestrial forest orchid from African and Asian woodlands, prized for tall spikes of violet to mauve flowers above broad, pleated leaves. Unlike epiphytic orchids, it roots in humus-rich soil and tolerates lower light, making it a rewarding shade-loving species for warm, humid, frost-free conditions.

Cold limit: USDA 10-11 (grown frost-free; indoor/greenhouse in most US climates) · RHS H1c (16-28°C)

What calanthe sylvatica's hardiness rating actually means

Calanthe sylvatica 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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-11 (grown frost-free; indoor/greenhouse in most US 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 5 °C (and never frost). Calanthe sylvatica has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for calanthe sylvatica as it gets too cold:

Below about about 5 °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 calanthe sylvatica go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above 5 °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 calanthe sylvatica can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Calanthe sylvatica hardiness — frequently asked questions

Is calanthe sylvatica cold hardy?

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

What is the minimum temperature calanthe sylvatica can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Calanthe sylvatica has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is calanthe sylvatica?

Calanthe sylvatica is rated USDA 10-11 (grown frost-free; indoor/greenhouse in most US climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can calanthe sylvatica survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 calanthe sylvatica below its minimum temperature?

Below about about 5 °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.