Sea Kale (Crambe maritima)

Perennial culinary kitchen garden vegetable
Description: Edible, bluish-green leaves emerge from the soil in early spring; showy, white, cruciform-shaped flowers developing by summer; attracts bees
Habit: Foliage and dense flower clusters grow to 30 inches high and 24 inches wide
Culture: Prefers light, mellow, well-drained garden loam and full sun
Hardiness: Cold hardy to USDA Zone 6
Origin: Europe
Attributes: Attracts bees
Jefferson documented
Thomas Jefferson first planted Sea Kale seed at Monticello in 1809 and continued cultivating this vegetable until 1822. Native to the seacoast of Great Britain, Western Europe, and the Black Sea, this hardy member of the cabbage family is grown for the early spring sprouts that arise from well-established plants (2 to 3 years old). The young leaves must be blanched, like celery or asparagus, to prevent a bitter flavour when cooked. In his 1815 Garden Calendar Jefferson recorded harvesting Sea Kale from April 1 to 28, but he was not using blanching pots until after 1821 when he ordered 500 “earthen pots for covering plants of Sea Kale” from a pottery near Richmond, VA.
Arrives in a 2 quart pot.

Sea Kale Seed ‘Lillywhite’

This vegetable long pre-dates Victorian times and was once most popular. The blanched shoots, young flower heads and very young leaves can be eaten raw or the leaf midribs cooked and eaten like Asparagus; forced Seakale is also a real delicacy.

As the name implies, Seakale is often found growing near the sea on beaches, cliffs and rocks and is tolerant of both salt air and drought.

If you have an exposed area of the garden where little else will grow, consider Seakale as it will happily colonise it and turn non-productive ground into something productive.

  • Seakale seed has a corky outside layer which allows it to float at sea for several years and so germination can be slow.
  • Soak seed in a bowl of fresh water for at least 24 hours.
  • Sow 1″ (2.5 cm) deep in trays of moist compost and keep well watered.
  • After germination transplant into modules or small pots and grow on under protection.
  • When plants are 2-3″ (5-7.5 cm) tall set out 2 feet (60 cm) apart in rows 2 feet (60 cm) apart.
  • Sow seed 1″ deep in trays of moist compost.
  • Seakale is a close relative to Brassicas so avoid planting in soil infected with clubroot.
  • Grow as you would cabbages, cleaning up any dead or damaged foliage as required.
  • Do not start forcing plants until their third full growing season.
  • Plants will deteriorate and need replacing after 5-7 years of cropping (ie approximately ten years from when first started).
  • Forcing Seakale
  • Seakale can be forced and blanched where it has grown (meaning the same plants can be used for several years) or can be lifted and forced in warmer conditions (resulting in the plants being discarded after forcing); forcing in situ is therefore the most practical way.
  • Forcing In Situ
  • Any time after the leaves have died right back, from autumn until January clear away the old leaf debris.
  • Cover the crowns with about 3″ (7.5 cm) of dry leaves which will help to insulate the crown.
  • Now cover the individual crowns with buckets or similar – traditional clay seakale forcing pots are perfect but virtually impossible to find! Whatever you use the pots should be around 12″ (30 cm) in diameter and at least 15″ (37.5 cm) tall and must completely exclude the light. Ensure they are firmly held down so they do not blow away.
  • Shoots are usually ready for cutting within about 3 months and ideally should be 4-8″ (10-20 cm) long when cut. Use a sharp knife to cut them low down with a little piece of root attached.
  • Stop cutting in May and uncover plants allowing them to regrow.
  • They can then be forced again the following season.
  • Forcing Indoors
  • Dig up the crowns after the first frost.
  • Pot up into gritty compost or pack into boxes or crates and place in a greenhouse or cool room.
  • Exclude all light with buckets, up-turned pots or similar.
  • Cut shoots as they appear, ideally at about 4-8″ (10-20 cm) long.
  • At the end of the sason you will probably need to dispose of the plants.

Buy Flower, Vegetable and Plant Seeds from Chiltern Seeds

Germination Instructions

Sow indoors immediately. Sow 12mm deep into moist well-drained seed compost. Ideal temp. 18°C for 6-8 weeks. Renowned for germinating irregularly over a long period. If germination does not occur cold stratify. Move to 5°C. for 6-8 weeks. Repeat process until germination occurs. Transplant seedlings once large enough to handle to 8cm pots. Plant out to final position once 10cm tall in rows 75cm apart with 75cm spacing.

Growing Instructions

Prefers deep, fertile, well-drained soil in full sun. Provide shelter from strong winds. Does not like to be cramped. Young plants may suffer slug attack, treat as required.

Cultivation Instructions

Clear any dead or damaged foliage as required. The seed pods do not open but drop off allowing seeds to germinate around the parent plant. Transplant small seedlings asap. Propagate by division in spring or autumn.

When to Sow

MarM AprA MayM JunJ JulJ AugA SepS OctO NovN DecD JanJ FebF
  • Sow Under Cover/Plant Indoors
  • Flowers/Harvest

Sea Kale

Like true kale, it is in the Brassica family. Also like true kale it produces edible, nourishing and tasty foliage. Unlike true kale it also produces edible shoots , roots and flower heads. The shoots have been compared to Asparagus, the foliage is like a cross between spinach and cabbage and the flower heads when permitted to develop are similar to broccoli.

From one plant we get facsimiles of Kale, cabbage, asparagus and broccoli. It also has edible and aesthetic landscaping value. Sounds too good to be true, which leaves one to ponder why it was never commercialized since its been known since at least the dark ages. It’s one major drawback is that it has an extremely limited shelf life – very short storage period and does not lend itself well to shipping.

Sea Kale can be grown from divisions planted either in the spring or fall. Root cuttings should be dormant and are best started in containers until they produce viable seedlings. They can also be started directly from seeds, unfortunately – like the plant itself, the seeds have a very short shelf life and must be from the current season – even then the germination rate is usually below standard so be sure to plant more than you will need.

Direct seeding into the garden is feasible in Spring, keep the seed bed and subsequent seedlings well watered for best results. Although direct seeding is works best results come from seeds started indoor in peat pots or cell packs and transplanted outdoors at an opportune time, soil temperatures should be at the very least 40 – 45 F.

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