Cold hardiness & minimum temperature

Is Common Star of Bethlehem (Ornithogalum umbellatum)cold hardy? Hardiness zone & min temp

Also called Common star of Bethlehem, Star of Bethlehem, Nap-at-noon, Eleven o'clock lady.

More about common star of bethlehem

About Common Star of Bethlehem

Ornithogalum umbellatum · also called Common star of Bethlehem, Star of Bethlehem · flowering

Ornithogalum umbellatum is a low-growing spring-flowering bulb native to southern Europe and the eastern Mediterranean, widely naturalised across the UK, North America, and temperate gardens worldwide. It produces flat-topped clusters of glistening white, star-shaped flowers with a distinctive green stripe on the outer surface of each petal, opening only in sunshine — hence the folk name 'nap-at-noon'. It is an exceptionally easy and resilient garden bulb that naturalises freely in grass or borders and requires virtually no maintenance once established; however, it can become invasive in favourable conditions, so consider its siting carefully. All Ornithogalum species are toxic to cats and dogs.

Cold limit: USDA 4-9 · RHS H6 (-25 to 22°C)

What common star of bethlehem's hardiness rating actually means

Yes — common star of bethlehem is genuinely cold hardy. Rated RHS H6 and USDA 4-9, 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 4-9 — 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. Common Star of Bethlehem is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for common star of bethlehem 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 common star of bethlehem go outside or overwinter — and where?

Plant it out within USDA 4-9 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 common star of bethlehem can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Common Star of Bethlehem hardiness — frequently asked questions

Is common star of bethlehem cold hardy?

Yes — common star of bethlehem is genuinely cold hardy. Rated RHS H6 and USDA 4-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Common Star of Bethlehem is hardy across USDA 4-9; 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 common star of bethlehem can survive?

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

What hardiness zone is common star of bethlehem?

Common Star of Bethlehem is rated USDA 4-9 and RHS H6 — Hardy throughout the UK and northern Europe.

Can common star of bethlehem survive winter outside?

Plant it out within USDA 4-9 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 common star of bethlehem 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.