Cold hardiness & minimum temperature

Is Crossandra (firecracker flower) (Crossandra infundibuliformis)cold hardy? Hardiness zone & min temp

Also called firecracker flower, firecracker plant.

More about crossandra (firecracker flower)

About Crossandra (firecracker flower)

Crossandra infundibuliformis · also called firecracker flower, firecracker plant · flowering

Crossandra is a tender tropical from the acanthus family, grown indoors for its fan-shaped orange, salmon or coral flowers that appear almost year-round. It wants bright indirect light, warmth and steadily moist soil. The ASPCA lists Crossandra as non-toxic to cats, dogs and horses, so it is pet-safe.

Cold limit: USDA 10a-11b outdoors; grown as a houseplant or under glass elsewhere · RHS H1b (tender; indoor or heated greenhouse in the UK, can summer outdoors above ~12°C) (18-27°C)

Watch for — Sudden leaf or flower drop: Usually from letting the soil dry out completely, cold draughts, or temperatures dipping below about 13-15°C.

What crossandra (firecracker flower)'s hardiness rating actually means

Crossandra (firecracker flower) 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 10a-11b outdoors; grown as a houseplant or under glass elsewhere — 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). Crossandra (firecracker flower) has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for crossandra (firecracker flower) 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 crossandra (firecracker flower) 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 crossandra (firecracker flower) can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Crossandra (firecracker flower) hardiness — frequently asked questions

Is crossandra (firecracker flower) cold hardy?

Crossandra (firecracker flower) 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. Crossandra (firecracker flower) can only live outside year-round in genuinely frost-free climates (roughly USDA 10a-11b outdoors; grown as a houseplant or under glass elsewhere); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature crossandra (firecracker flower) can survive?

What hardiness zone is crossandra (firecracker flower)?

Crossandra (firecracker flower) is rated USDA 10a-11b outdoors; grown as a houseplant or under glass elsewhere and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can crossandra (firecracker flower) 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 crossandra (firecracker flower) 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.