Cold hardiness & minimum temperature

Is Alisma plantago-aquatica (Alisma plantago-aquatica)cold hardy? Hardiness zone & min temp

Also called Water Plantain, Common Water Plantain, Mad Dog Weed.

More about alisma plantago-aquatica

About Alisma plantago-aquatica

Alisma plantago-aquatica · also called Water Plantain, Common Water Plantain · flowering

Water plantain is an elegant native marginal with a basal rosette of long-stalked, plantain-like oval leaves and an airy, much-branched panicle of tiny pale lilac three-petalled flowers in summer. It thrives in shallow pond edges and wet mud, self-seeds freely and is valued for its delicate flower clouds in wildlife ponds.

Cold limit: USDA 5-9 (fully hardy, herbaceous, dies back) · RHS H7 (5-25°C)

What alisma plantago-aquatica's hardiness rating actually means

Yes — alisma plantago-aquatica is genuinely cold hardy. Rated RHS H7 and USDA 5-9 (fully hardy, herbaceous, dies back), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. On the US scale that maps to USDA 5-9 (fully hardy, herbaceous, dies back) — 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 below about −20 °C. Alisma plantago-aquatica is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for alisma plantago-aquatica as it gets too cold:

It tolerates winter lows to about −20 °C once established.
Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root.
First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.

Can alisma plantago-aquatica go outside or overwinter — and where?

Plant it out within USDA 5-9 (fully hardy, herbaceous, dies back) and it overwinters with little or no help.
It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy.
The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

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 alisma plantago-aquatica can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Alisma plantago-aquatica hardiness — frequently asked questions

Is alisma plantago-aquatica cold hardy?

Yes — alisma plantago-aquatica is genuinely cold hardy. Rated RHS H7 and USDA 5-9 (fully hardy, herbaceous, dies back), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Alisma plantago-aquatica is hardy across USDA 5-9 (fully hardy, herbaceous, dies back); it belongs in the ground or a frost-proof container, not on a windowsill, and many types actively need a cold winter to perform.

What is the minimum temperature alisma plantago-aquatica can survive?

Minimum survivable temperature is roughly below about −20 °C. Alisma plantago-aquatica is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is alisma plantago-aquatica?

Alisma plantago-aquatica is rated USDA 5-9 (fully hardy, herbaceous, dies back) and RHS H7 — Hardy in the severest European continental winters.

Can alisma plantago-aquatica survive winter outside?

Plant it out within USDA 5-9 (fully hardy, herbaceous, dies back) and it overwinters with little or no help. It does not want to come indoors — a warm winter room actually weakens a hardy plant by denying it dormancy. The real risks in its range are waterlogging, wind-rock on young plants, and a late hard frost on new growth — not ordinary winter cold.

What happens to alisma plantago-aquatica below its minimum temperature?

It tolerates winter lows to about −20 °C once established. Below its rated zone, the visible damage is browned or blackened top growth and, in the worst case, a killed crown or root. First-year, newly planted, or container-grown specimens are noticeably less hardy than established garden plants — the roots are exposed.