Forever greens

On the vague off chance that you haven’t yet noticed, might I mention the fact that kale

is trending? Once dismissed as tasteless fodder crops, this leafy, flavoursome, nutritious, ultra-hardy, versatile vegetable is now on the menus of the smartest restaurants, whether blanched and sautéed, steamed, deep-fried, or used in salads, soups, smoothies, stews, casseroles and curries.

Of the many varieties that are cultivated, I enjoy growing two in particular. One is the Tuscan kale known as ‘Cavolo Nero’ or ‘Nero di Toscana’, a tall, elegant plant with stiffly plumed, dimpled leaves of the deepest inky blue-green.

An 18th-century heirloom variety, this good-looking, tasty kale has long been a favourite of gardeners, including Thomas Jefferson, former president of the US, who grew it in his famous gardens at Monticello in Virginia.

The other variety I grow is the Russian kale known as ‘Ragged Jack’, another heritage kale with a long and rich history of cultivation, whose sweet, tender oak-shaped pale green leaves are flushed through with pink.

Both plants are highly ornamental, delicious additions to both the kitchen and the flower garden, easily grown from seed each year in late spring/early summer to produce large plants productive over many months.

But while I wouldn’t be without either of them, for the first time ever I’m also growing a third kind – a very special kale that (for now, at least) I’m calling ‘Glin Castle Perennial Kale’.

This vegetable is the sort of plant that kitchen gardeners and permaculturists dream about. Firstly, it’s properly perennial, with a life span of at least four to five years, after which you simply grow new plants from cuttings. Secondly, it’s astonishingly productive, throwing out tender new leaves at such a lick that just one or two mature plants can keep a family in a regular supply of tasty, nutritious leaves for most of the year.

Thirdly, it’s surprisingly easy to grow, the only proviso being that, like any member of the cabbage family, it must be protected against snails/slugs as well as netted against the cabbage white butterfly.

The catch (there’s almost always a catch), is that neither the seed nor young plants are often seen for sale. Why? Well, when it comes to the scarcity of seed, the explanation is a straightforward one; it only very rarely flowers and even then, only very occasionally sets seed.

But growing it from a cutting is a different matter entirely. Stick a piece of it in the ground (or in a pot) and it will root with willing abandon. It’s this quality that makes the scarcity of plants for sale so inexplicable (I’ve never seen perennial kale on the shelves of an Irish garden centre, for example, or listed in the catalogues of an Irish nursery).

In fact, short of sourcing perennial kale by mail order from one of the few specialist European suppliers (see below), the only way I know of getting your muddy hands on a plant is by being given it as a gift, the very same way by which it has survived in cultivation for so long.

I've wanted to grow it ever since coming across it in the community gardens of St Raphael's in Co Waterford a few years ago, when it was described to me as cottier's kale (a variant of cottager's kale), a plant long cultivated in Ireland. It had come there as a cutting given to the Michelin-starred chef Martijn Kajuiter by Darina Allen.

But others say that the plant growing in the gardens of St Raphael’s is another equally rare, heritage variety of perennial kale known as Daubenton’s kale, named either after the French town of Daubenton or to commemorate the French naturalist Louis-Jean-Marie Daubenton. Both Daubenton’s kale and Cottager’s kale are distinct varieties as recognised by Victorian plantsmen.

Whichever rare kind of perennial kale it is – Daubenton's or Cottager's – I finally got my wish this summer when Dublin gardener Helen Dillon gave me a generous handful of stem cuttings taken from a flourishing, bushy specimen growing in her garden. Potted on and placed in the greenhouse, these have already begun to show such vigorous growth that they'll soon be ready to plant out .

This kale originally came to Dillon from the walled kitchen garden of Glin Castle in Co Limerick some 15 years ago, as a gift from Olda Fitzgerald, wife of the late Knight of Glin.

Dillon remembers watching the castle's head gardener, Tom Wall, one summer's day, as he planted neat lines of cuttings directly into the ground – yet more proof of how easily it can be cultivated.

As to how the plant first arrived in the gardens of Glin Castle, I subsequently discovered the answer while reading the book Irish Traditional Cooking, by Darina Allen, who grows it in her Cork garden. She describes how one of the cooks at Glin Castle, May Liston, originally brought "slips of this vegetable from her home in Lower Athea and she gave me some to plant".

The plant I’m calling ‘Glin Castle Perennial Kale’ prefers a deep, fertile, slightly acidic soil in full sun, but will tolerate less than ideal conditions, growing quickly to form a large, bushy plant roughly 90cm in height and spread.

If you happen to see it growing in a friend’s garden, my advice is to stare at it longingly until you’re offered a cutting.

Failing that, Somerset-based Pennard Plants (pennardplants.com) will supply both plain and variegated Daubenton’s perennial kale (but not cottager’s kale) by mail-order. Irish nursery and garden centre owners, take note.