Cold hardiness & minimum temperature

Is Ernest's Turk's Cap (Melocactus ernestii)cold hardy? Hardiness zone & min temp

Also called Turk's Cap Cactus, Ernest Melocactus.

More about ernest's turk's cap

About Ernest's Turk's Cap

Melocactus ernestii · also called Turk's Cap Cactus, Ernest Melocactus · houseplant

Ernest's Turk's Cap is a handsome Brazilian cactus that develops a distinctive reddish woolly-bristly cephalium atop its globose, many-ribbed body as it matures. Small pink to red flowers appear from the cephalium regularly. It is a challenging but rewarding collector's plant requiring tropical warmth and high light. Not toxic to pets; spines are a physical hazard.

Cold limit: USDA 10-12 (indoor-only in most climates) · RHS H1c (18-30°C)

Watch for — Root rot: Caused by overwatering or waterlogged soil. Ensure free drainage and observe careful watering discipline, especially in winter.

What ernest's turk's cap's hardiness rating actually means

Ernest's Turk's Cap 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 10-12 (indoor-only 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 5 °C (and never frost). Ernest's Turk's Cap has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for ernest's turk's cap 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 ernest's turk's cap 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 ernest's turk's cap can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Ernest's Turk's Cap hardiness — frequently asked questions

Is ernest's turk's cap cold hardy?

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

What is the minimum temperature ernest's turk's cap can survive?

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

What hardiness zone is ernest's turk's cap?

Ernest's Turk's Cap is rated USDA 10-12 (indoor-only in most climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can ernest's turk's cap 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 ernest's turk's cap 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.