Cold hardiness & minimum temperature

Is Spanish Sea Kale (Crambe hispanica)cold hardy? Hardiness zone & min temp

Also called Spanish sea kale, Spanish colewort, Abyssinian kale.

More about spanish sea kale

About Spanish Sea Kale

Crambe hispanica · also called Spanish sea kale, Spanish colewort · edible

Crambe hispanica is a slender annual herb of the Brassicaceae family, native to the Mediterranean region from the Iberian Peninsula to western Iran, where it grows in grassland, disturbed ground, and cultivated fields. It grows to about 1 m tall, with lyrate-pinnate lower leaves and branching racemes of small white four-petalled flowers, and is related to the cultivated oilseed form grown commercially as Abyssinian kale. Young leaves are edible and the seeds yield an oil high in erucic acid used in industrial applications. No specific ASPCA toxicity data exists; as a Brassicaceae plant with no known toxic alkaloids it is considered mildly-toxic by precaution rather than confirmed safe.

Cold limit: USDA 7-10 · RHS H3 (5–30°C)

What spanish sea kale's hardiness rating actually means

Hardiness works differently for spanish sea kale: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". Its RHS rating of H3 means: Half-hardy — comes through mild UK winters outside but is killed by a hard freeze. On the US scale that maps to USDA 7-10 — 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

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

Concretely, for spanish sea kale as it gets too cold:

Light frost (around 0 to −2 °C) damages or kills tender summer crops outright; cold-hardy types take a few degrees of frost.
The plant does not "survive winter" — its life cycle simply ends, by design, when frost arrives or it finishes cropping.
A surprise late spring frost can also kill young transplants set out too early, before the season even starts.

Can spanish sea kale go outside or overwinter — and where?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost.
In short-season zones, start it indoors or under cover to stretch the effective growing window.
Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

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 spanish sea kale can be outside. US growers can check USDA zones; UK growers should use the RHS hardiness ratings, which match the H3 figure above.

Frost protection for borderline spanish sea kale

Spanish Sea Kale is right on a hardiness edge in many gardens, so if you are pushing it, these measures buy it the margin it needs:

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks.
Have row cover ready for an unexpected late spring or early autumn frost.
Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.

Spanish Sea Kale hardiness — frequently asked questions

Is spanish sea kale cold hardy?

Hardiness works differently for spanish sea kale: it is grown as a seasonal crop, not overwintered. The question is not "what zone" but "how long is your frost-free growing window". A seasonal crop, not a perennial. Spanish Sea Kale is grown as an annual in USDA 7-10; you sow after the last frost and harvest before the first one, then start again next year.

What is the minimum temperature spanish sea kale can survive?

As an annual crop, its "minimum temperature" is the first hard frost — that is the end of the plant's life, not a survivable low. Many types are also damaged by light frost (around 0 °C).

What hardiness zone is spanish sea kale?

Spanish Sea Kale is rated USDA 7-10 and RHS H3 — Half-hardy — comes through mild UK winters outside but is killed by a hard freeze.

Can spanish sea kale survive winter outside?

Time it to your frost dates: sow or plant out after the last spring frost, and aim to harvest before the first autumn frost. In short-season zones, start it indoors or under cover to stretch the effective growing window. Hardier crops in this group can be sown for an autumn or overwintered harvest in mild zones — check the specific crop.

How do I protect spanish sea kale from frost?

Use fleece, cloches or a cold frame at each end of the season to dodge a borderline frost and add growing weeks. Have row cover ready for an unexpected late spring or early autumn frost. Know your local last- and first-frost dates and count back the crop’s days-to-maturity to schedule the sowing.