Cold hardiness & minimum temperature

Is Daylily (Hemerocallis spp.)cold hardy? Hardiness zone & min temp

Also called day lily, orange daylily, ditch lily, tawny daylily.

More about daylily

About Daylily

Hemerocallis spp. · also called day lily, orange daylily · flowering

Daylilies are tough, clump-forming perennials whose lily-like blooms each last a single day, opening in succession through summer. Easy and vigorous in the garden. Despite not being a true lily, they are just as deadly to cats.

Cold limit: USDA 3-9 · RHS H7 (15-27°C)

What daylily's hardiness rating actually means

Yes — daylily is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H7 means: Hardy in the severest European continental winters. 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 below about −20 °C. Daylily is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for daylily as it gets too cold:

It tolerates winter lows to about −20 °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 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 can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Daylily hardiness — frequently asked questions

Is daylily cold hardy?

Yes — daylily is genuinely cold hardy. Rated RHS H7 and USDA 3-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Daylily 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 can survive?

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

What hardiness zone is daylily?

Daylily is rated USDA 3-9 and RHS H7 — Hardy in the severest European continental winters.

Can daylily 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 below its minimum temperature?

It tolerates winter lows to about −20 °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.