Cold hardiness & minimum temperature

Is Pencil-leaf Tylecodon (Tylecodon cacalioides)cold hardy? Hardiness zone & min temp

Also called Pencil-leaf Tylecodon, Sulphur Butterbush.

More about pencil-leaf tylecodon

About Pencil-leaf Tylecodon

Tylecodon cacalioides · also called Pencil-leaf Tylecodon, Sulphur Butterbush · houseplant

A shrubby South African succulent with peeling yellow-grey bark and tufts of narrow, cylindrical grey-green leaves at branch tips. Grows larger than most Tylecodon in cultivation, reaching around 1 m. Winter-growing, summer-dormant. Bears yellow-green tubular flowers in late summer on leafless branches. Toxic to pets and livestock — contains bufadienolide compounds found across the genus.

Cold limit: USDA 10b–11b · RHS H1c (10–32 °C (optimal); avoid prolonged exposure below 2 °C)

What pencil-leaf tylecodon's hardiness rating actually means

Pencil-leaf Tylecodon 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 10b–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 5 °C (and never frost). Pencil-leaf Tylecodon has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for pencil-leaf tylecodon 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 pencil-leaf tylecodon 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 pencil-leaf tylecodon can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

Pencil-leaf Tylecodon hardiness — frequently asked questions

Is pencil-leaf tylecodon cold hardy?

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

What is the minimum temperature pencil-leaf tylecodon can survive?

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

What hardiness zone is pencil-leaf tylecodon?

Pencil-leaf Tylecodon is rated USDA 10b–11b and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can pencil-leaf tylecodon 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 pencil-leaf tylecodon 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.