Cold hardiness & minimum temperature

Is Rainbow Plant (Byblis liniflora)cold hardy? Hardiness zone & min temp

Also called Rainbow Plant, Northern Rainbow Plant, Annual Rainbow Plant.

More about rainbow plant

About Rainbow Plant

Byblis liniflora · also called Rainbow Plant, Northern Rainbow Plant · tropical

Byblis liniflora is a fast-growing annual carnivorous plant native to northern Australia, where it occurs in seasonally wet, nutrient-poor sandy soils. Its thread-like leaves are densely coated with mucilage-secreting glands that glisten like a rainbow in bright light, trapping small insects; in late summer it produces numerous vivid pink-purple flowers that self-pollinate freely. It loves heat and bright direct light, completing its entire life cycle in a single growing season. Byblis is not listed by the ASPCA; treat with caution around pets as the sticky enzymes may cause mild irritation.

Cold limit: USDA 11-12 (grown as annual in cooler climates) · RHS H1a (15–35 °C)

What rainbow plant's hardiness rating actually means

Rainbow Plant 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 (grown as annual in cooler climates) — 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). Rainbow Plant has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

Concretely, for rainbow plant 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 rainbow plant 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 rainbow plant can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H1a figure above.

Rainbow Plant hardiness — frequently asked questions

Is rainbow plant cold hardy?

Rainbow Plant 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. Rainbow Plant can only live outside year-round in genuinely frost-free climates (roughly USDA 11-12 (grown as annual in cooler climates)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature rainbow plant can survive?

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

What hardiness zone is rainbow plant?

Rainbow Plant is rated USDA 11-12 (grown as annual in cooler climates) and RHS H1a — Tropical — needs a heated room or greenhouse; no frost tolerance whatsoever.

Can rainbow plant 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 rainbow plant 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.