Cold hardiness & minimum temperature

Is Orange Clock Vine (Thunbergia gregorii)cold hardy? Hardiness zone & min temp

Also called Orange Thunbergia, Gregorii Clock Vine, African Sky Vine.

More about orange clock vine

About Orange Clock Vine

Thunbergia gregorii · also called Orange Thunbergia, Gregorii Clock Vine · tropical

Thunbergia gregorii is an eye-catching tender perennial twining vine from East Africa, valued for its rich, clear orange tubular flowers produced almost continuously in warm climates. It grows rapidly and performs well on trellises, pergolas, and in hanging baskets. Generally considered pet-safe, with no toxic-family signals in the genus.

Cold limit: USDA 9-12 (grown as annual in cooler zones) · RHS H1c (15-32°C)

Watch for — Frost damage: Frost-tender; bring containers indoors before the first frost or treat as an annual in cool-temperate climates.

What orange clock vine's hardiness rating actually means

Orange Clock Vine 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 9-12 (grown as annual in cooler zones) — 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). Orange Clock Vine has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Orange Clock Vine hardiness — frequently asked questions

Is orange clock vine cold hardy?

Orange Clock Vine 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. Orange Clock Vine can only live outside year-round in genuinely frost-free climates (roughly USDA 9-12 (grown as annual in cooler zones)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature orange clock vine can survive?

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

What hardiness zone is orange clock vine?

Orange Clock Vine is rated USDA 9-12 (grown as annual in cooler zones) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can orange clock vine 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 orange clock vine 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.