Cold hardiness & minimum temperature

Is Daylily 'Hyperion' (Hemerocallis 'Hyperion')cold hardy? Hardiness zone & min temp

Also called Hyperion daylily, lemon yellow daylily, classic yellow daylily.

More about daylily 'hyperion'

About Daylily 'Hyperion'

Hemerocallis 'Hyperion' · also called Hyperion daylily, lemon yellow daylily · flowering

Hemerocallis 'Hyperion' is one of the most celebrated daylily cultivars of the 20th century, bearing large, lemon-yellow, fragrant blooms in mid-summer on tall elegant scapes. Raised in 1925, it remains a benchmark for grace and fragrance in the genus. Highly toxic to cats — all parts can cause acute, fatal kidney failure.

Cold limit: USDA 3-9 · RHS H6 (5-35°C)

What daylily 'hyperion''s hardiness rating actually means

Yes — daylily 'hyperion' 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 'Hyperion' is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for daylily 'hyperion' 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 'hyperion' 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 'hyperion' can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Daylily 'Hyperion' hardiness — frequently asked questions

Is daylily 'hyperion' cold hardy?

Yes — daylily 'hyperion' 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 'Hyperion' 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 'hyperion' can survive?

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

What hardiness zone is daylily 'hyperion'?

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

Can daylily 'hyperion' 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 'hyperion' 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.