Cold hardiness & minimum temperature

Is Broadway's Melon Cactus (Melocactus broadwayi)cold hardy? Hardiness zone & min temp

Also called Broadway's Turk's Cap Cactus, Caribbean Melon Cactus.

More about broadway's melon cactus

About Broadway's Melon Cactus

Melocactus broadwayi · also called Broadway's Turk's Cap Cactus, Caribbean Melon Cactus · houseplant

A globose to barrel-shaped cactus native to the Lesser Antilles and Trinidad, forming a characteristic woolly-bristly red cephalium once mature. Small pink to purple flowers emerge from the cephalium throughout the warm season. Like all Melocactus, it requires consistent warmth and full sun; cold and waterlogging are fatal.

Cold limit: USDA 11-12 (indoor-only outside tropics) · RHS H1b (16-35°C)

Watch for — Root rot in cool, wet conditions: Temperature below 16°C combined with moist soil is rapidly fatal. Keep at minimum 18°C indoors through winter.

What broadway's melon cactus's hardiness rating actually means

Broadway's Melon Cactus 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 11-12 (indoor-only outside tropics) — 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). Broadway's Melon Cactus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for broadway's melon cactus 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 broadway's melon cactus 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 broadway's melon cactus can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Broadway's Melon Cactus hardiness — frequently asked questions

Is broadway's melon cactus cold hardy?

Broadway's Melon Cactus 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. Broadway's Melon Cactus can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (indoor-only outside tropics)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature broadway's melon cactus can survive?

What hardiness zone is broadway's melon cactus?

Broadway's Melon Cactus is rated USDA 11-12 (indoor-only outside tropics) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can broadway's melon cactus 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 broadway's melon cactus 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.