Cold hardiness & minimum temperature

Is Daylily 'Double River Wye' (Hemerocallis 'Double River Wye')cold hardy? Hardiness zone & min temp

Also called Double River Wye daylily, double cream daylily, double white daylily.

More about daylily 'double river wye'

About Daylily 'Double River Wye'

Hemerocallis 'Double River Wye' · also called Double River Wye daylily, double cream daylily · flowering

Hemerocallis 'Double River Wye' is a distinctive double-flowered daylily bearing large, cream-white blooms with extra petaloid segments that create a full, rose-like appearance in mid-summer. It is a classic British-raised cultivar with a gentle fragrance. Toxic to cats — the entire plant including pollen can cause acute, life-threatening kidney failure.

Cold limit: USDA 3-9 · RHS H6 (5-32°C)

Watch for — Crown rot: In poorly drained soils, especially over winter, the crown may rot. Improve drainage, avoid mulching directly against the crown, and lift and inspect clumps showing decline.

What daylily 'double river wye''s hardiness rating actually means

Yes — daylily 'double river wye' is genuinely cold hardy. Rated RHS H6 and USDA 3-9, 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 3-9 — 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. Daylily 'Double River Wye' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for daylily 'double river wye' 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 daylily 'double river wye' go outside or overwinter — and where?

Plant it out within USDA 3-9 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 daylily 'double river wye' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Daylily 'Double River Wye' hardiness — frequently asked questions

Is daylily 'double river wye' cold hardy?

Yes — daylily 'double river wye' is genuinely cold hardy. Rated RHS H6 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Daylily 'Double River Wye' is hardy across USDA 3-9; 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 daylily 'double river wye' can survive?

Minimum survivable temperature is roughly about −20 to −15 °C. Daylily 'Double River Wye' is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is daylily 'double river wye'?

Daylily 'Double River Wye' is rated USDA 3-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can daylily 'double river wye' survive winter outside?

Plant it out within USDA 3-9 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 daylily 'double river wye' 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.