Crambe maritima used to be a familiar sight at the back of shingle beaches along the south coast of England and the West Country, where it was regularly cut as a spring delicacy. For centuries, aficionados made sure the young stems were blanched for best flavour, avoiding the bitterness of the green shoots. The shingle helped with blanching and foragers guaranteed the best results by piling more stones round the swelling shoots, often topping up with seaweed.
Like many other plants, sea kale was a hit in Victorian times, as Patrick Neill, the first secretary of the Caley – or, if we're being formal, the Royal Caledonian Horticultural Society – noted in 1838: "It has within these few years become a vegetable of common occurrence in the markets both of London and Edinburgh." Since then, after over-enthusiastic harvesting and disturbance at the back of beaches, it's now become a rare sight. There are still a few clumps along the Solway estuary and in Fife.
Even though you can't, and shouldn't, harvest the few remaining wild plants, there's nothing to stop you growing your own. Sea kale seed and young thongs are widely available. I, for one, wouldn't be without my sea kale crop in March and April, as pickings from the veg garden at that time are few and far between.
Once established, this short-lived perennial is fairly undemanding but it needs a different regime to other brassicas. It has never been developed as a kitchen garden vegetable, so it thrives best in its natural environment. The soil should mirror the back of beaches – gritty, very free-draining and in full sun. Without this, a plant's crown rots. The ground where I first planted sea kale many years ago gradually became shadier, and as nutrients from further up the garden leached down the hill, the soil became overly rich. The new sunny site is perfect.
Sow, prick out and plant in the usual way. While Patrick Neill wrote: "If manure be added, it should consist of seaweed or half-rotted leaves of trees," my 21st-century alternative is a scattering of seaweed meal. Plants should be 60cm apart in a veg patch, but a mature specimen looks impressive and would sit nicely in a border. The blue-green glaucus leaves are striking and thick stems produce broad, frothy panicles, crammed with white flowers. Their strong waft of honey is not to be missed on a sunny day.
Be sure to save some of the large seeds and bring on one or two new plants every year to replace older specimens or ones that don't survive the winter. The plants die back naturally in autumn, so clear away dead vegetation, cut back any stems and prepare the ground for a spring harvest.
Well-blanched stems have a clean, delicate flavour, not unlike asparagus. According to Neill, Sir George S MacKenzie, in his Memoirs Of The Caledonian Society, related how he covered the ground with clean, dry oat straw and had it changed whenever it became musty. A fine method with an army of gardeners, but it would be hard to replace the straw without damaging young shoots.
Neill's solution is better: "Convenient blanching-pots with movable lids have been constructed for the express purpose. It may be proper to provide 30 to 60 such pots."
The Victorians never did anything by half: I find five or six sea kale pots are quite enough. My old Cornish pots are family heirlooms and, given the price of new ones, large plastic containers are nearly as good. When the first buds appear early in January, I cover the crown and wait a couple of months, checking progress by lifting the lids. I remove the pot and cut back all the stems once they're 30-45cm tall. You'd need to prevent a plastic pot from blowing away by weighing down with a stone or earthing up round the sides. Neill packed horse muck round his pots and "raised [it] up to about a foot above them". This all sounds a bit of a palaver but, with techniques like this, he enjoyed a sea kale harvest from November to May, even in Scotland.
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