Cold hardiness & minimum temperature

Is Mysore trumpetvine (Thunbergia mysorensis)cold hardy? Hardiness zone & min temp

Also called Mysore trumpetvine, Mysore clock vine, Indian clock vine, Brick and butter vine.

More about mysore trumpetvine

About Mysore trumpetvine

Thunbergia mysorensis · also called Mysore trumpetvine, Mysore clock vine · tropical

Mysore trumpetvine is a spectacular evergreen woody climber from the Western Ghats of southern India, producing dramatic pendulous racemes of large chocolate-red and yellow tubular flowers year-round in warm climates. Best grown in a heated glasshouse or tropical garden. Thunbergia is not listed as toxic by the ASPCA and is considered safe around pets.

Cold limit: USDA 10-12 · RHS H1c (13–32°C)

Watch for — Bud drop: Sudden loss of flower buds is typically caused by a sharp drop in temperature, cold draughts, or very dry air. Maintain temperatures above 13°C (55°F), keep away from draughts, and mist regularly to maintain humidity.

What mysore trumpetvine's hardiness rating actually means

Mysore trumpetvine 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 — 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). Mysore trumpetvine has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Mysore trumpetvine hardiness — frequently asked questions

Is mysore trumpetvine cold hardy?

Mysore trumpetvine 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. Mysore trumpetvine can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature mysore trumpetvine can survive?

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

What hardiness zone is mysore trumpetvine?

Mysore trumpetvine is rated USDA 10-12 and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can mysore trumpetvine 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 mysore trumpetvine 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.