Cold hardiness & minimum temperature

Is Costus Woodsonii (Costus woodsonii)cold hardy? Hardiness zone & min temp

Also called red button ginger, scarlet spiral flag.

More about costus woodsonii

About Costus Woodsonii

Costus woodsonii · also called red button ginger, scarlet spiral flag · tropical

Costus woodsonii is a clumping tropical spiral ginger from Central America, grown for its glossy dark leaves spiralling up cane-like stems and its red, cone-shaped flower heads tipped with small yellow-orange blooms. A spiral ginger (Costaceae), not a true ginger, it thrives in warmth, humidity and bright indirect light, grown indoors or in frost-free gardens.

Cold limit: USDA 9-11 (indoor/glasshouse in most of the US and UK) · RHS H1b (18-29°C)

Watch for — Rhizome rot: Cold, soggy, poorly drained soil rots the rhizomes. Use a free-draining mix, water more sparingly in cool weather and ensure the pot drains freely so rhizomes never sit in water.

What costus woodsonii's hardiness rating actually means

Costus Woodsonii 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 9-11 (indoor/glasshouse in most of the US and UK) — 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). Costus Woodsonii has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Costus Woodsonii hardiness — frequently asked questions

Is costus woodsonii cold hardy?

Costus Woodsonii 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. Costus Woodsonii can only live outside year-round in genuinely frost-free climates (roughly USDA 9-11 (indoor/glasshouse in most of the US and UK)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature costus woodsonii can survive?

What hardiness zone is costus woodsonii?

Costus Woodsonii is rated USDA 9-11 (indoor/glasshouse in most of the US and UK) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can costus woodsonii 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 costus woodsonii 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.