Cold hardiness & minimum temperature

Is Cobra Lily (Darlingtonia californica)cold hardy? Hardiness zone & min temp

Also called Cobra lily, Cobra plant, California pitcher plant, Cobra orchid.

More about cobra lily

About Cobra Lily

Darlingtonia californica · also called Cobra lily, Cobra plant · houseplant

The cobra lily is a carnivorous pitcher plant native to cold-water bogs of northern California and Oregon, named for its hooded, snake-like trap. It demands cool roots, distilled water, sunlight, and a winter dormancy, making it a challenging specialist plant. ASPCA lists it as non-toxic to cats, dogs, and horses.

Cold limit: USDA 7a-10b (outdoors); needs a cold winter dormancy (Cool roots below 21C; air to ~27C, hardy to about -9C dormant)

Watch for — Warm roots / heat stress: The number-one killer. Roots suffer above roughly 50-60F sustained and can die quickly; symptoms are sudden wilting, browning, and collapse. Cool the roots with cold water flushes, ice cubes, shaded or insulated pots, or a cool spot.

What cobra lily's hardiness rating actually means

Cobra Lily 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 7a-10b (outdoors); needs a cold winter dormancy — 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). Cobra Lily has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Cobra Lily hardiness — frequently asked questions

Is cobra lily cold hardy?

Cobra Lily 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. Cobra Lily can only live outside year-round in genuinely frost-free climates (roughly USDA 7a-10b (outdoors); needs a cold winter dormancy); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature cobra lily can survive?

Minimum survivable temperature is roughly about 10 °C (sustained cold below this is damaging). Cobra Lily has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

What hardiness zone is cobra lily?

Cobra Lily is rated USDA 7a-10b (outdoors); needs a cold winter dormancy and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can cobra lily 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 cobra lily 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.