Cold hardiness & minimum temperature

Is Wherry's Foamflower (Tiarella wherryi)cold hardy? Hardiness zone & min temp

Also called Wherry's Foamflower, Wherry's Foam Flower, Coolwort.

More about wherry's foamflower

About Wherry's Foamflower

Tiarella wherryi · also called Wherry's Foamflower, Wherry's Foam Flower · flowering

Tiarella wherryi is a compact, clump-forming herbaceous perennial native to moist, shaded woodlands in the southern Appalachian Mountains of the eastern United States. Unlike many Tiarella, it is a non-running clumper that increases slowly from underground rhizomes, making it excellent for controlled understorey planting. It grows best in cool, humus-rich, moist but well-drained soil in partial to full shade and holds the RHS Award of Garden Merit. Tiarella wherryi is not listed on the ASPCA toxic plant database; it is generally considered of low toxicity, though a formal ASPCA non-toxic listing is absent.

Cold limit: USDA 4-8 · RHS H5 (-20 to 25°C)

What wherry's foamflower's hardiness rating actually means

Yes — wherry's foamflower is genuinely cold hardy. Rated RHS H5 and USDA 4-8, 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 4-8 — 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. Wherry's Foamflower is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for wherry's 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 wherry's foamflower go outside or overwinter — and where?

Plant it out within USDA 4-8 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 wherry's foamflower can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Wherry's Foamflower hardiness — frequently asked questions

Is wherry's foamflower cold hardy?

Yes — wherry's foamflower is genuinely cold hardy. Rated RHS H5 and USDA 4-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Wherry's Foamflower is hardy across USDA 4-8; 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 wherry's foamflower can survive?

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

What hardiness zone is wherry's foamflower?

Wherry's Foamflower is rated USDA 4-8 and RHS H5 — Hardy in most of the UK and in cold winters.

Can wherry's foamflower survive winter outside?

Plant it out within USDA 4-8 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 wherry's 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.