Cold hardiness & minimum temperature

Is Waras' Cryptanthus (Cryptanthus warasii)cold hardy? Hardiness zone & min temp

Also called Waras' Cryptanthus, Waras Earth Star.

More about waras' cryptanthus

About Waras' Cryptanthus

Cryptanthus warasii · also called Waras' Cryptanthus, Waras Earth Star · houseplant

Cryptanthus warasii is a rare Brazilian terrestrial bromeliad forming large, robust rosettes with stiff, strap-like leaves edged with fine teeth. Compared to most Cryptanthus species it can develop impressive size while retaining the characteristic star-shaped silhouette. It thrives in high humidity, indirect light, and root-zone watering, excelling in warm terrariums and greenhouses.

Cold limit: USDA 11–12 · RHS H1a (19–30°C)

Watch for — Slow offset production: Pups develop after flowering, but the timeline varies. Stress — particularly low light or cold temperatures — delays offset formation. Once pups appear and reach 10–12 cm, remove and pot them on to propagate new plants.

What waras' cryptanthus's hardiness rating actually means

Waras' Cryptanthus 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 H1a means: Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever. On the US scale that maps to USDA 11–12 — 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 above about 15 °C (warm, never cold). Waras' Cryptanthus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for waras' cryptanthus as it gets too cold:

Below about above about 15 °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 waras' cryptanthus go outside or overwinter — and where?

It can holiday outdoors in summer once nights are reliably above above 15 °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 waras' cryptanthus can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Waras' Cryptanthus hardiness — frequently asked questions

Is waras' cryptanthus cold hardy?

Waras' Cryptanthus 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. Waras' Cryptanthus can only live outside year-round in genuinely frost-free climates (roughly USDA 11–12); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature waras' cryptanthus can survive?

Minimum survivable temperature is roughly above about 15 °C (warm, never cold). Waras' Cryptanthus has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is waras' cryptanthus?

Waras' Cryptanthus is rated USDA 11–12 and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can waras' cryptanthus survive winter outside?

It can holiday outdoors in summer once nights are reliably above above 15 °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 waras' cryptanthus below its minimum temperature?

Below about above about 15 °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.