Cold hardiness & minimum temperature

Is Red Tower Ginger (Costus barbatus)cold hardy? Hardiness zone & min temp

Also called Red Tower Ginger, Spiral Ginger, Red Velvet Ginger.

More about red tower ginger

About Red Tower Ginger

Costus barbatus · also called Red Tower Ginger, Spiral Ginger · tropical

Costus barbatus is a vigorous tropical perennial native to Costa Rica and Panama, prized for its tall cone-like red bracts that persist for weeks and the small yellow flowers emerging from them. It performs best in part shade with reliably moist, fertile soil and high humidity. Note: plants sold in the nursery trade as Costus barbatus are often botanically Costus comosus var. bakeri, but the care requirements are identical. The ASPCA does not list Costus on its database; treat as mildly toxic and keep away from pets.

Cold limit: USDA 9b-11 · RHS H1b (18–30°C)

What red tower ginger's hardiness rating actually means

Red Tower Ginger 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 9b-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 about 10 °C (sustained cold below this is damaging). Red Tower Ginger has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for red tower ginger 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 red tower ginger 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 red tower ginger can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1b figure above.

Red Tower Ginger hardiness — frequently asked questions

Is red tower ginger cold hardy?

Red Tower Ginger 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. Red Tower Ginger can only live outside year-round in genuinely frost-free climates (roughly USDA 9b-11); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature red tower ginger can survive?

What hardiness zone is red tower ginger?

Red Tower Ginger is rated USDA 9b-11 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can red tower ginger 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 red tower ginger 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.