Cold hardiness & minimum temperature

Is Super King Ixora (Ixora coccinea 'Super King')cold hardy? Hardiness zone & min temp

Also called Super King Ixora, Super King Flame of the Woods.

More about super king ixora

About Super King Ixora

Ixora coccinea 'Super King' · also called Super King Ixora, Super King Flame of the Woods · tropical

Super King Ixora is a vigorous cultivar of Ixora coccinea selected for its exceptionally large flower clusters of brilliant red-orange blooms. More free-flowering and bolder than the species, it is a popular landscape shrub across tropical and subtropical regions, commonly used as a hedge or specimen. It requires acidic soil and full sun for best performance.

Cold limit: USDA 10-12 · RHS H1a (18-38°C)

Watch for — Bud drop after transport or repotting: Environmental changes — moving location, root disturbance, or temperature shock — frequently cause bud drop. After purchase or repotting, keep the plant in stable conditions; do not move a budding plant. Consistent warmth and light help buds develop to open flowers.

What super king ixora's hardiness rating actually means

Super King Ixora 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 H1a means: Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever. 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 above about 15 °C (warm, never cold). Super King Ixora has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for super king ixora as it gets too cold:

Below about above about 15 °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 super king ixora go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above above 15 °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 super king ixora can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Super King Ixora hardiness — frequently asked questions

Is super king ixora cold hardy?

Super King Ixora 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. Super King Ixora 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 super king ixora can survive?

Minimum survivable temperature is roughly above about 15 °C (warm, never cold). Super King Ixora has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is super king ixora?

Super King Ixora is rated USDA 10-12 and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can super king ixora survive winter outside?

It can holiday outdoors in summer once nights are reliably above above 15 °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 super king ixora below its minimum temperature?

Below about above about 15 °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.