Cold hardiness & minimum temperature

Is kidney-leaved bladderwort (Utricularia reniformis)cold hardy? Hardiness zone & min temp

Also called kidney-leaved bladderwort, giant bladderwort.

More about kidney-leaved bladderwort

About kidney-leaved bladderwort

Utricularia reniformis · also called kidney-leaved bladderwort, giant bladderwort · houseplant

One of the most striking bladderworts, Utricularia reniformis is a large epiphytic to terrestrial carnivore from the coastal mountains of southern Brazil. It produces dramatic kidney-shaped leaves up to 7 cm wide and imposing lilac flower scapes reaching 60 cm tall. It thrives in cool-to-intermediate humidity-rich terrarium or greenhouse conditions.

Cold limit: USDA 10-11 · RHS H1c (13–26°C days; 10–18°C nights preferred)

Watch for — Failure to flower without a cool night drop: In the wild this highland species experiences cool nights (10–15°C). Consistently warm nights above 20°C discourage flowering. Provide a 5–10°C temperature drop at night using an unheated room or open window during summer evenings to encourage scapes.

What kidney-leaved bladderwort's hardiness rating actually means

kidney-leaved bladderwort 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 10-11 — 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 5 °C (and never frost). kidney-leaved bladderwort has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for kidney-leaved bladderwort 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 kidney-leaved bladderwort 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 kidney-leaved bladderwort can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1c figure above.

kidney-leaved bladderwort hardiness — frequently asked questions

Is kidney-leaved bladderwort cold hardy?

kidney-leaved bladderwort 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. kidney-leaved bladderwort can only live outside year-round in genuinely frost-free climates (roughly USDA 10-11); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature kidney-leaved bladderwort can survive?

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

What hardiness zone is kidney-leaved bladderwort?

kidney-leaved bladderwort is rated USDA 10-11 and RHS H1c — Warm-temperate — can summer outdoors but must come in well before the first frost.

Can kidney-leaved bladderwort 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 kidney-leaved bladderwort 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.