Cold hardiness & minimum temperature

Is Rayed Broom (Genista radiata)cold hardy? Hardiness zone & min temp

Also called Rayed broom, Rayed-branch broom, Starry broom.

More about rayed broom

About Rayed Broom

Genista radiata · also called Rayed broom, Rayed-branch broom · flowering

Genista radiata is a compact, deciduous shrub native to rocky hillsides, open scrubland, and dry grasslands from the central Mediterranean into the Balkans, distinguished by its whorled, radiating branches and bright yellow pea-flowers in late spring. It is an ornamental broom suitable for rock gardens, dry slopes, and gravel gardens, valued for its tidy, architectural growth habit and tolerance of poor, dry conditions. As with all broom species in the legume family, it likely contains quinolizidine alkaloids and should be treated as mildly toxic to cats and dogs. Never prune into old wood.

Cold limit: USDA 6-9 · RHS H5 (-15 to 35°C)

What rayed broom's hardiness rating actually means

Yes — rayed broom is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H5 means: Hardy in most of the UK and in cold winters. On the US scale that maps to USDA 6-9 — 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 −15 to −10 °C. Rayed Broom is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for rayed broom as it gets too cold:

It tolerates winter lows to about −15 to −10 °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 rayed broom go outside or overwinter — and where?

Plant it out within USDA 6-9 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 rayed broom can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Rayed Broom hardiness — frequently asked questions

Is rayed broom cold hardy?

Yes — rayed broom is genuinely cold hardy. Rated RHS H5 and USDA 6-9, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Rayed Broom is hardy across USDA 6-9; 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 rayed broom can survive?

Minimum survivable temperature is roughly about −15 to −10 °C. Rayed Broom is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is rayed broom?

Rayed Broom is rated USDA 6-9 and RHS H5 — Hardy in most of the UK and in cold winters.

Can rayed broom survive winter outside?

Plant it out within USDA 6-9 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 rayed broom below its minimum temperature?

It tolerates winter lows to about −15 to −10 °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.