Cold hardiness & minimum temperature

Is Rat Tail Cactus (Disocactus flagelliformis)cold hardy? Hardiness zone & min temp

Also called Rat tail cactus, Rat's tail cactus, Rattail cactus.

More about rat tail cactus

About Rat Tail Cactus

Disocactus flagelliformis · also called Rat tail cactus, Rat's tail cactus · houseplant

Rat tail cactus (Disocactus flagelliformis) is a trailing epiphytic cactus prized for slim, bristly stems that spill over a hanging pot and burst into vivid magenta spring flowers. Give it bright light, fast-draining cactus mix and a cool, dry winter rest. ASPCA does not list it, so treat as unverified and keep its spines away from pets.

Cold limit: USDA 10-11 (frost-tender; grow indoors or under cover in cooler climates) (18-27C in growth; 7-13C winter rest)

Watch for — No flowers: Usually means too little light or no cool, dry winter rest. Give it the brightest spot possible and keep it cool and barely watered from late autumn to early spring to set magenta blooms.

What rat tail cactus's hardiness rating actually means

Rat Tail Cactus 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 (frost-tender; grow indoors or under cover in cooler 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). Rat Tail Cactus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for rat tail cactus 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 rat tail cactus 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 rat tail cactus can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Rat Tail Cactus hardiness — frequently asked questions

Is rat tail cactus cold hardy?

Rat Tail Cactus 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. Rat Tail Cactus can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11 (frost-tender; grow indoors or under cover in cooler climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature rat tail cactus can survive?

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

What hardiness zone is rat tail cactus?

Rat Tail Cactus is rated USDA 10-11 (frost-tender; grow indoors or under cover in cooler climates) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can rat tail cactus 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 rat tail cactus 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.