Cold hardiness & minimum temperature
Is Super King Ixora Red (Ixora casei 'Super King')cold hardy? Hardiness zone & min temp
Also called Super King Ixora Red, Super King Ixora, Taiwanese Ixora.
More about super king ixora red
About Super King Ixora Red
Ixora casei 'Super King' · also called Super King Ixora Red, Super King Ixora · tropical
Super King Ixora Red is a large, vigorous tropical evergreen shrub bearing spectacular extra-large clusters of brilliant red flowers. It thrives in full sun, acidic well-drained soil, and high humidity—conditions it rewards with near year-round bloom. Non-toxic to pets. Ideal for tropical hedges, foundation plantings, and large containers.
Cold limit: USDA 9a–11b · RHS H1b (18–35 °C)
What super king ixora red's hardiness rating actually means
Super King Ixora Red 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 H1b means: Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season. On the US scale that maps to USDA 9a–11b — 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 10 °C (sustained cold below this is damaging). Super King Ixora Red has no frost tolerance at all — it is an indoor plant in any climate with a real winter.
Concretely, for super king ixora red as it gets too cold:
- Below about about 10 °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 red go outside or overwinter — and where?
- It can holiday outdoors in summer once nights are reliably above 10 °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 red can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.
Super King Ixora Red hardiness — frequently asked questions
Is super king ixora red cold hardy?
Super King Ixora Red 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 Red can only live outside year-round in genuinely frost-free climates (roughly USDA 9a–11b); everywhere else it is a houseplant that summers out at most.
What is the minimum temperature super king ixora red can survive?
Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Super King Ixora Red 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 red?
Super King Ixora Red is rated USDA 9a–11b and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.
Can super king ixora red survive winter outside?
It can holiday outdoors in summer once nights are reliably above 10 °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 red below its minimum temperature?
Below about about 10 °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.
Keep reading
- Super King Ixora Red care — the full brief (light, water, soil, problems, pet safety)
- USDA hardiness zones — find yours and what grows there
- Is super king ixora red hardy in the UK? — the RHS-rating version
- RHS hardiness ratings — the UK system explained
- Frost-date calculator — your real outdoor window
- The USDA hardiness zone map, explained
- Is xanthosoma albomarginatum cold hardy?
- Is xanthosoma atrovirens cold hardy?
- Is alocasia wollongong cold hardy?
- All 6887plant hardiness & min-temp guides