Cold hardiness & minimum temperature

Is 'Purple Sprouting' Broccoli (Brassica oleracea var. italica 'Purple Sprouting')cold hardy? Hardiness zone & min temp

Also called Purple sprouting broccoli, PSB.

More about 'purple sprouting' broccoli

About 'Purple Sprouting' Broccoli

Brassica oleracea var. italica 'Purple Sprouting' · also called Purple sprouting broccoli, PSB · edible

Purple sprouting broccoli is a hardy, overwintering brassica grown for masses of slender purple flower shoots in late winter and spring, rather than a single head. Sown in late spring, it stands through winter cold (which it needs to crop well) before bursting into productive spears. It demands firm, fertile soil, full sun, staking, and patience over its long 9-12 month season.

Cold limit: USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C) · RHS H5 (7-24°C)

Watch for — Wind-rock: Tall winter plants loosen in the soil during gales, tearing roots. Plant firmly, earth up the stems, and stake individually in exposed sites.

What 'purple sprouting' broccoli's hardiness rating actually means

Yes — 'purple sprouting' broccoli is genuinely cold hardy. Rated RHS H5 and USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C), 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 7-9 (overwinters outdoors; many cultivars hardy to around -12°C) — 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. 'Purple Sprouting' Broccoli is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for 'purple sprouting' broccoli 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 'purple sprouting' broccoli go outside or overwinter — and where?

Plant it out within USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C) 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 'purple sprouting' broccoli can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H5 figure above.

Frost protection for borderline 'purple sprouting' broccoli

'Purple Sprouting' Broccoli is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

At the cold edge of its range, mulch the root zone in late autumn to buffer the deepest freezes.
Protect container specimens — pots freeze through far faster than open ground, costing roughly a zone of hardiness.
Shelter new growth from late spring frosts with fleece if a hard night is forecast.

'Purple Sprouting' Broccoli hardiness — frequently asked questions

Is 'purple sprouting' broccoli cold hardy?

Yes — 'purple sprouting' broccoli is genuinely cold hardy. Rated RHS H5 and USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. 'Purple Sprouting' Broccoli is hardy across USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C); 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 'purple sprouting' broccoli can survive?

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

What hardiness zone is 'purple sprouting' broccoli?

'Purple Sprouting' Broccoli is rated USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C) and RHS H5 — Hardy in most of the UK and in cold winters.

Can 'purple sprouting' broccoli survive winter outside?

Plant it out within USDA 7-9 (overwinters outdoors; many cultivars hardy to around -12°C) 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.

How do I protect 'purple sprouting' broccoli from frost?

At the cold edge of its range, mulch the root zone in late autumn to buffer the deepest freezes. Protect container specimens — pots freeze through far faster than open ground, costing roughly a zone of hardiness. Shelter new growth from late spring frosts with fleece if a hard night is forecast.