Cold hardiness & minimum temperature

Is Glory Bower (Clerodendrum splendens)cold hardy? Hardiness zone & min temp

Also called Flaming Glorybower, Scarlet Glorybower, Red Clerodendrum.

More about glory bower

About Glory Bower

Clerodendrum splendens · also called Flaming Glorybower, Scarlet Glorybower · tropical

Clerodendrum splendens is a spectacular tropical twining shrub from West Africa bearing dense clusters of brilliant scarlet flowers against glossy dark-green foliage. It blooms most freely in late winter to spring in warm, humid conditions. Treat as mildly toxic to pets, as the Clerodendrum genus contains compounds that may cause gastrointestinal upset.

Cold limit: USDA 10-12 · RHS H1c (18-30°C)

Watch for — Leaf drop: Often triggered by temperature fluctuations, cold draughts, or underwatering; find a stable warm position away from draughts.

What glory bower's hardiness rating actually means

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

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

Glory Bower hardiness — frequently asked questions

Is glory bower cold hardy?

Glory Bower 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. Glory Bower 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 glory bower can survive?

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

What hardiness zone is glory bower?

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

Can glory bower 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 glory bower 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.