Cold hardiness & minimum temperature

Is 'Cavolo Nero' Kale (Brassica oleracea var. palmifolia 'Nero di Toscana')cold hardy? Hardiness zone & min temp

Also called Lacinato kale, Tuscan kale, Dinosaur kale, Black kale.

More about 'cavolo nero' kale

About 'Cavolo Nero' Kale

Brassica oleracea var. palmifolia 'Nero di Toscana' · also called Lacinato kale, Tuscan kale · edible

Cavolo nero is the Tuscan 'black' kale prized for its long, strappy, blue-black blistered leaves and deep, sweet flavour after frost. Exceptionally hardy and easy, it crops over a long cool season from late summer into winter. Grow in full sun and firm, fertile soil, picking leaves from the bottom up so the plant keeps producing for months.

Cold limit: USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°C) · RHS H4 (7-24°C)

What 'cavolo nero' kale's hardiness rating actually means

Yes — 'cavolo nero' kale is genuinely cold hardy. Rated RHS H4 and USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°C), it lives outdoors all year and needs winter cold rather than protection from it. Its RHS rating of H4 means: Hardy in an average winter across much of the temperate world. On the US scale that maps to USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°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 −10 to −5 °C. 'Cavolo Nero' Kale is built for winter — once established it takes hard frost and snow in its stride.

Concretely, for 'cavolo nero' kale as it gets too cold:

It tolerates winter lows to about −10 to −5 °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 'cavolo nero' kale go outside or overwinter — and where?

Plant it out within USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°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 'cavolo nero' kale can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H4 figure above.

Frost protection for borderline 'cavolo nero' kale

'Cavolo Nero' Kale 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.

'Cavolo Nero' Kale hardiness — frequently asked questions

Is 'cavolo nero' kale cold hardy?

Yes — 'cavolo nero' kale is genuinely cold hardy. Rated RHS H4 and USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°C), it lives outdoors all year and needs winter cold rather than protection from it. An outdoor plant. 'Cavolo Nero' Kale is hardy across USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°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 'cavolo nero' kale can survive?

Minimum survivable temperature is roughly about −10 to −5 °C. 'Cavolo Nero' Kale is built for winter — once established it takes hard frost and snow in its stride.

What hardiness zone is 'cavolo nero' kale?

'Cavolo Nero' Kale is rated USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°C) and RHS H4 — Hardy in an average winter across much of the temperate world.

Can 'cavolo nero' kale survive winter outside?

Plant it out within USDA 7-10 (overwinters outdoors; tolerates hard frost to around -10°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 'cavolo nero' kale 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.