Cold hardiness & minimum temperature

Is Herald Trumpet Vine (Beaumontia grandiflora)cold hardy? Hardiness zone & min temp

Also called Easter Lily Vine, Nepal Trumpet Flower, White Herald Trumpet.

More about herald trumpet vine

About Herald Trumpet Vine

Beaumontia grandiflora · also called Easter Lily Vine, Nepal Trumpet Flower · tropical

Herald Trumpet Vine is a spectacular evergreen climber from the Himalayas and India, grown for its large, fragrant white trumpet flowers up to 12 cm long produced in spring. A vigorous grower requiring substantial support, it is best suited to warm frost-free climates or a large heated conservatory. Treat as toxic given its Apocynaceae family membership.

Cold limit: USDA 10-12 · RHS H1c (5 to 38°C)

Watch for — Failure to flower: Most common cause is insufficient light or an absent winter dry rest. Ensure at least 6 hours of direct sun and reduce watering markedly from autumn through winter.

What herald trumpet vine's hardiness rating actually means

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

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

Herald Trumpet Vine hardiness — frequently asked questions

Is herald trumpet vine cold hardy?

Herald Trumpet 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. Herald Trumpet Vine 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 herald trumpet vine can survive?

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

What hardiness zone is herald trumpet vine?

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

Can herald trumpet 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 herald trumpet 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.