How to Grow Sea Kale

Soil & Growing Conditions

Soil pH range

6.5 7.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

Stage	BBCH	Notes
Propagation	0	Sow seed in pots in spring or autumn, divide in early spring, or take 15cm root cuttings (thongs) in late autumn -- straight cut nearest the plant, slanting cut at the far end -- and store upright in damp sand until March (RHS, Gardeners World).
Planting and establishment	1	Plant thongs in early spring under about 2cm of compost, or with the strongest bud 2.5cm below the surface, in a sheltered, sunny, sharply drained site; plants take 2-5 years to reach full size (RHS, Gardeners World).
Crown building and flowering	5	Leave the crown unforced through its first year to build strength; mature plants make mounds of blue-green wavy-edged leaves topped with small white flowers in early summer (RHS).
Forcing and harvest	4	From the second year onwards, cover crowns over winter with a rhubarb forcer or upturned bucket; snap or cut the pale blanched shoots once finger length or more and eat raw or steamed (Gardeners World).

Quick Facts

Factor	Value
Soil pH	6.5 - 7.5
Optimal growing temp	14-24°C
Minimum survivable temp	-5°C
Drainage	Well-drained
Lifecycle	perennial
Edible parts	blanched shoots, leaves, flowering shoots

At a Glance

Harvest & Storage

When to pick: RHS: shoots grown for eating are "usually blanched for several weeks before harvesting"; young wavy-edged blue-green leaves are also edible and used as a cooked vegetable, and young flowering shoots bearing small white flowers are "cooked like sprouting broccoli".

Storage

Best used fresh soon after blanching and harvest

Diseases

Club root

Plasmodiophora brassicae

Pests

Slugs

Gastropoda (slugs, various spp.)

Cabbage caterpillars

Pieris brassicae; Pieris rapae; Pieris napi; Mamestra brassicae; Plutella xylostella

Sources

1. BBC Gardeners World Magazine - How to Grow Sea Kale

   Grow in well-drained soil in full sun, though it tolerates poor soil and partial shade. Plant thongs (root cuttings) into compost in early spring under a 2cm layer of compost. Traditional root-cutting method: cut 15cm thongs from the roots in late autumn with a straight cut at the end nearest the plant and a slanting cut at the far end, tie into bundles and store upright in slightly damp sand somewhere cool with the tops just below the surface; the following March, when buds are just breaking, rub out all but the strongest bud and plant with the buds 2.5cm below the surface. To eat, force the plants over winter under a bucket or rhubarb forcer for tender young shoots eaten raw or steamed -- but not until the second year, as forcing earlier weakens the plant. Snap or cut the shoots when finger length or more and steam.

2. FAO EcoCrop - Crambe maritima data sheet
3. GBIF - GBIF Backbone Taxonomy: Crambe maritima

These 3 sources are specific to this region. The full list of 7 sources behind this guide (BBC Gardeners World Magazine, FAO EcoCrop, GBIF and others) is in the references of our UK guide to sea kale; they describe the plant itself, which is the same wherever it grows.