Cold hardiness & minimum temperature

Is Common Broom (Cytisus scoparius)cold hardy? Hardiness zone & min temp

Also called Common broom, Scotch broom, Broom.

More about common broom

About Common Broom

Cytisus scoparius · also called Common broom, Scotch broom · flowering

Cytisus scoparius is a deciduous to semi-evergreen shrub native to western and central Europe, common on heathlands, dry banks, and road verges across the British Isles. It produces masses of bright yellow pea-flowers on arching green stems in late spring and early summer and is adapted to dry, infertile, acidic soils in full sun. The key care rule is to never cut into old wood — pruning must always leave green stems — as the plant does not regenerate from bare wood and old untended plants quickly become untidy and collapse. Common broom is toxic to dogs and cats due to quinolizidine alkaloids.

Cold limit: USDA 5-8 · RHS H6 (-20°C to 35°C)

Watch for — Broom gall mite (Aceria genistae): Causes tight, cauliflower-like galls at stem tips; prune out affected growth in winter. The mite is species-specific and does not spread to other garden plants.

What common broom's hardiness rating actually means

Yes — common broom is genuinely cold hardy. Rated RHS H6 and USDA 5-8, 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 5-8 — 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 about −20 to −15 °C. Common Broom is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for common broom 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 broom go outside or overwinter — and where?

Plant it out within USDA 5-8 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 common broom can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H6 figure above.

Common Broom hardiness — frequently asked questions

Is common broom cold hardy?

Yes — common broom is genuinely cold hardy. Rated RHS H6 and USDA 5-8, it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. Common Broom is hardy across USDA 5-8; 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 common broom can survive?

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

What hardiness zone is common broom?

Common Broom is rated USDA 5-8 and RHS H6 — Hardy throughout the UK and northern Europe.

Can common broom survive winter outside?

Plant it out within USDA 5-8 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 common broom 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.