Cold hardiness & minimum temperature

Is Maple-Leaved Waterleaf (Hydrophyllum canadense)cold hardy? Hardiness zone & min temp

Also called Maple-Leaved Waterleaf, Canada Waterleaf, Mapleleaf Waterleaf, Bluntleaf Waterleaf.

More about maple-leaved waterleaf

About Maple-Leaved Waterleaf

Hydrophyllum canadense · also called Maple-Leaved Waterleaf, Canada Waterleaf · herb

Hydrophyllum canadense is a shade-tolerant woodland perennial native to moist hardwood forests from New England south through the Appalachians to Alabama and west to Missouri. Its distinctively maple-shaped palmate leaves make it one of the most recognisable waterleafs; coiled clusters of white to pale lavender flowers appear in late spring to early summer, nestled just below the upper leaves. It forms spreading colonies by scaly rhizomes and works well as a low groundcover under tall trees. Hydrophyllum is not listed in the ASPCA plant database; classified mildly-toxic as a precaution.

Cold limit: USDA 4-7 · RHS H6 (-28 to 24°C)

What maple-leaved waterleaf's hardiness rating actually means

Yes — maple-leaved waterleaf is genuinely cold hardy. Rated RHS H6 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H6 means: Hardy throughout the UK and northern Europe. On the US scale that maps to USDA 4-7 — 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 −20 to −15 °C. Maple-Leaved Waterleaf is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for maple-leaved waterleaf as it gets too cold:

It tolerates winter lows to about −20 to −15 °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 maple-leaved waterleaf go outside or overwinter — and where?

Plant it out within USDA 4-7 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 maple-leaved waterleaf can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Maple-Leaved Waterleaf hardiness — frequently asked questions

Is maple-leaved waterleaf cold hardy?

Yes — maple-leaved waterleaf is genuinely cold hardy. Rated RHS H6 and USDA 4-7, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Maple-Leaved Waterleaf is hardy across USDA 4-7; 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 maple-leaved waterleaf can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Maple-Leaved Waterleaf is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is maple-leaved waterleaf?

Maple-Leaved Waterleaf is rated USDA 4-7 and RHS H6 — Hardy throughout the UK and northern Europe.

Can maple-leaved waterleaf survive winter outside?

Plant it out within USDA 4-7 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 maple-leaved waterleaf below its minimum temperature?

It tolerates winter lows to about −20 to −15 °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.