Cold hardiness & minimum temperature

Is Blue Pickerelweed (Pontederia azurea)cold hardy? Hardiness zone & min temp

Also called Blue Pickerelweed, Anchored Water Hyacinth, Azure Pickerelweed.

More about blue pickerelweed

About Blue Pickerelweed

Pontederia azurea · also called Blue Pickerelweed, Anchored Water Hyacinth · flowering

Pontederia azurea is a rooted, emergent aquatic perennial from South America bearing vivid blue-violet flower spikes above broad, heart-shaped leaves from summer into autumn. Unlike the free-floating common water hyacinth, it anchors in shallow water or wet margins. A striking pond marginal plant valued for its intense flower colour and long bloom season; less aggressively invasive than P. crassipes.

Cold limit: USDA 8–11 · RHS H1b (5–38°C (active growth 18–35°C))

Watch for — Rhizome rot in cold waterlogged soil: In climates below zone 8, cold, stagnant water in winter can rot the rhizome. In marginal zones, lift and overwinter the rhizome in a frost-free location in moist soil or a bucket of water indoors, replanting after the last frost.

What blue pickerelweed's hardiness rating actually means

Blue Pickerelweed 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 8–11 — 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 10 °C (sustained cold below this is damaging). Blue Pickerelweed has no frost tolerance at all — it is an indoor plant in any climate with a real winter.

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

Blue Pickerelweed hardiness — frequently asked questions

Is blue pickerelweed cold hardy?

Blue Pickerelweed 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 Pickerelweed can only live outside year-round in genuinely frost-free climates (roughly USDA 8–11); everywhere else it is a houseplant that summers out at most.

What is the minimum temperature blue pickerelweed can survive?

What hardiness zone is blue pickerelweed?

Blue Pickerelweed is rated USDA 8–11 and RHS H1b — Sub-tropical — a normal warm home is fine, but it cannot go outside in a cool season.

Can blue pickerelweed 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 pickerelweed 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.