Cold hardiness & minimum temperature

Is Heartleaf Foamflower (Tiarella cordifolia)cold hardy? Hardiness zone & min temp

Also called Heartleaf foamflower, Foamflower, False mitrewort, Coolwort.

More about heartleaf foamflower

About Heartleaf Foamflower

Tiarella cordifolia · also called Heartleaf foamflower, Foamflower · flowering

Tiarella cordifolia is a low-growing, colony-forming woodland perennial native to eastern North America, where it carpets the floors of moist, shaded deciduous forests from Nova Scotia to Georgia. It produces frothy spikes of tiny creamy-white to pale-pink flowers in spring above heart-shaped, attractively lobed leaves that often develop burgundy markings and bronze autumn tones. As a reliable, low-maintenance ground cover for deep shade, it is one of the most versatile native woodland plants for UK and US gardens, holding an RHS Award of Garden Merit. Tiarella cordifolia is considered non-toxic to cats and dogs.

Cold limit: USDA 3-8 · RHS H5 (-20 to 30°C)

What heartleaf foamflower's hardiness rating actually means

Yes — heartleaf foamflower is genuinely cold hardy. Rated RHS H5 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 3-8 — 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 −15 to −10 °C. Heartleaf Foamflower is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for heartleaf foamflower as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 heartleaf foamflower go outside or overwinter — and where?

Plant it out within USDA 3-8 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 heartleaf foamflower can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Heartleaf Foamflower hardiness — frequently asked questions

Is heartleaf foamflower cold hardy?

Yes — heartleaf foamflower is genuinely cold hardy. Rated RHS H5 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Heartleaf Foamflower is hardy across USDA 3-8; 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 heartleaf foamflower can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Heartleaf Foamflower is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is heartleaf foamflower?

Heartleaf Foamflower is rated USDA 3-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can heartleaf foamflower survive winter outside?

Plant it out within USDA 3-8 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 heartleaf foamflower below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.