UK hardiness
Is Water Canna hardy in the UK?
Canna glauca
More about water canna in the UK
Water Canna and the RHS hardiness rating
Water Canna is rated RHS H2 — tender, meaning it withstands winter minimums of about 1 to 5°C. In practice that means it needs a frost-free greenhouse or indoors over winter — a UK frost will kill it. The RHS rating describes an absolute minimum temperature, not an average: a single hard frost below its band is what does the damage, so the question is always "what is the coldest night my garden gets?", not "what is a typical winter here?".
This follows the RHS plant hardiness rating system (H1a–H7), the UK standard. For the US growing-zone view, see the water canna USDA hardiness guide.
Does UK region change it?
Because water canna is frost-tender, UK region matters less than the simple rule: it does not stay outdoors over winter anywhere in the UK. Treat any time outside as a summer holiday — bring it back indoors once nights drop toward 10°C, well before the first frost, and acclimatise it over a week each way so the leaves do not shock.
Overwintering water canna in the UK
Overwintering water canna in the UK means bringing it in: a bright, frost-free room or a heated glasshouse, watered sparingly while growth slows. Do not leave it against cold glass or near an unheated porch. Move it back out only after the last spring frost has passed for your area.
Water Canna UK hardiness — frequently asked questions
Is water canna hardy in the UK?
Water Canna is rated RHS H2 (tender, hardy to about 1 to 5°C). It is not winter-hardy anywhere in the UK and must be overwintered under cover.
Can water canna stay outside over winter in the UK?
No. Water Canna is frost-tender — a UK frost will kill it. Bring it indoors or into a frost-free greenhouse before the first autumn frost and return it outside only after the last spring frost.
What does RHS H2 mean?
RHS hardiness ratings run H1a (needs a heated glasshouse) to H7 (survives below -20°C). Water Canna's rating, H2, means tender — it tolerates winter minimums of about 1 to 5°C. The rating is an absolute minimum, not an average.
How do I overwinter water canna in the UK?
Overwintering water canna in the UK means bringing it in: a bright, frost-free room or a heated glasshouse, watered sparingly while growth slows. Do not leave it against cold glass or near an unheated porch. Move it back out only after the last spring frost has passed for your area.
Does UK region change whether water canna survives?
Because water canna is frost-tender, UK region matters less than the simple rule: it does not stay outdoors over winter anywhere in the UK. Treat any time outside as a summer holiday — bring it back indoors once nights drop toward 10°C, well before the first frost, and acclimatise it over a week each way so the leaves do not shock.
More water canna care
See the full water canna care guide, its temperature & humidity needs, and the US (USDA) hardiness version of this page.