Cold hardiness & minimum temperature

Is Prickly Crossandra (Crossandra pungens)cold hardy? Hardiness zone & min temp

Also called Prickly Crossandra, Firecracker Plant.

More about prickly crossandra

About Prickly Crossandra

Crossandra pungens · also called Prickly Crossandra, Firecracker Plant · flowering

A low-growing African Crossandra species with dark, glossy, spine-tipped leaves and vivid yellow-to-orange flower spikes that attract butterflies and hummingbirds. More heat-tolerant than the Indian species, it works as a groundcover or container plant in tropical and subtropical gardens. Needs bright light, consistent moisture, and warmth to flower freely.

Cold limit: USDA 10–11 · RHS H1a (18–30°C)

Watch for — Sparse or no flowering: Insufficient light is the primary cause. Move to a brighter position with filtered sun. Ensure temperatures remain above 18°C and avoid overfertilising with nitrogen, which promotes foliage at the expense of flowers.

What prickly crossandra's hardiness rating actually means

Prickly Crossandra 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 10–11 — 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). Prickly Crossandra has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for prickly crossandra 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 prickly crossandra 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 prickly crossandra can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Prickly Crossandra hardiness — frequently asked questions

Is prickly crossandra cold hardy?

Prickly Crossandra 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. Prickly Crossandra can only live outside year-round in genuinely frost-free climates (roughly USDA 10–11); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature prickly crossandra can survive?

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

What hardiness zone is prickly crossandra?

Prickly Crossandra is rated USDA 10–11 and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can prickly crossandra 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 prickly crossandra 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.