Cold hardiness & minimum temperature

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

Also called Spiral Flag, Red Pinecone Ginger, Barbados Costus.

More about red tower ginger

About Red Tower Ginger

Costus barbatus · also called Spiral Flag, Red Pinecone Ginger · tropical

Red Tower Ginger is a Central American tropical with spirally arranged leaves on twisting stems and showy scarlet cone-like bracts from which yellow flowers emerge. It is popular in tropical landscaping and as a bold container plant. Prefers warmth, humidity, and moist, fertile soil. Pet safety data is limited.

Cold limit: USDA 10-12 (indoor-only in most US homes) · RHS H1c (18-32°C)

Watch for — Leggy growth: Insufficient light causes stems to stretch; move to a brighter position or supplement with a grow light in winter.

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 H1c means: Warm-temperate — can summer outdoors but must come in well before the first frost. On the US scale that maps to USDA 10-12 (indoor-only in most US homes) — 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 5 °C (and never frost). 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 5 °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 5 °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 H1c 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 10-12 (indoor-only in most US homes)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature red tower ginger can survive?

Minimum survivable temperature is roughly about 5 °C (and never frost). Red Tower Ginger has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is red tower ginger?

Red Tower Ginger is rated USDA 10-12 (indoor-only in most US homes) and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can red tower ginger survive winter outside?

It can holiday outdoors in summer once nights are reliably above 5 °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 5 °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.