Cold hardiness & minimum temperature

Is Blue Water Lily (Nymphaea colorata)cold hardy? Hardiness zone & min temp

Also called African Blue Water Lily, Tropical Blue Lily.

More about blue water lily

About Blue Water Lily

Nymphaea colorata · also called African Blue Water Lily, Tropical Blue Lily · tropical

Blue Water Lily is a tropical African species producing delicate lilac-blue flowers above rounded floating pads. Unlike hardy species, it requires warm water year-round and is typically grown as an annual in temperate climates or overwintered indoors. Nymphaea is listed by the ASPCA as toxic to cats and dogs and should be kept away from pets.

Cold limit: USDA 10-12 (annual in cooler zones) · RHS H1b (21-32°C)

Watch for — Cold water shock: Water temperatures below 18°C stunt growth and prevent flowering. Do not place outdoor until water has warmed in late spring.

What blue water lily's hardiness rating actually means

Blue Water 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 10-12 (annual in cooler zones) — 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). Blue Water Lily has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Blue Water Lily hardiness — frequently asked questions

Is blue water lily cold hardy?

Blue Water 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. Blue Water Lily can only live outside year-round in genuinely frost-free climates (roughly USDA 10-12 (annual in cooler zones)); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature blue water lily can survive?

What hardiness zone is blue water lily?

Blue Water Lily is rated USDA 10-12 (annual in cooler zones) and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can blue water 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 blue water 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.