Cold hardiness & minimum temperature

Is Lily of the valley (Convallaria majalis)cold hardy? Hardiness zone & min temp

Also called May lily, May bells, our lady's tears.

About Lily of the valley

Convallaria majalis · also called May lily, May bells · flowering

Lily of the valley is a shade-loving perennial with broad green leaves and tiny fragrant white bells in late spring. Spreads by rhizome to make ground cover. Severely toxic to pets and people — every part contains cardiac glycosides.

Convallaria majalis is a rhizomatous herbaceous perennial of Europe and Central Asia (naturalized in temperate North America and invasive in parts of the northern US), forming a low 8–12 in groundcover of arching white bells.

Spreads aggressively by rhizome into dense colonies, becoming weedy/invasive in good conditions. SEVERELY toxic: all parts contain cardiac glycosides — primarily convallatoxin — causing arrhythmia, blood-pressure/heart-rate changes and potentially fatal heart failure; even vase water has killed pets. Wear gloves and site away from children and animals.

Cold limit: USDA 3-8 · RHS H7 (10-21°C)

Sources: missouribotanicalgarden.org, pmc.ncbi.nlm.nih.gov

What lily of the valley's hardiness rating actually means

Yes — lily of the valley is genuinely cold hardy. Rated RHS H7 and USDA 3-8, 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 3-8 — 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 below about −20 °C. Lily of the valley is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for lily of the valley 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 lily of the valley 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 lily of the valley can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H7 figure above.

Lily of the valley hardiness — frequently asked questions

Is lily of the valley cold hardy?

Yes — lily of the valley is genuinely cold hardy. Rated RHS H7 and USDA 3-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Lily of the valley 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 lily of the valley can survive?

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

What hardiness zone is lily of the valley?

Lily of the valley is rated USDA 3-8 and RHS H7 — Hardy in the severest European continental winters.

Can lily of the valley 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 lily of the valley 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.