Lollo rosso and other blushing heads

Another Life: The sudden rush into spring has the seakale pushing up succulent shoots in the garden (where I blanch them under pots in the dark) just as it does in the pebble banks that are the plant's natural home.

Of all the vegetables I grow, this is the closest to the wild original, grown from root cuttings passed between generations of keen kitchen gardeners.

A few others on my sowing chart - cabbages, carrots, beetroot - have wild ancestors within these islands. But broad beans, onions, celeriac and cucumbers came from Europe and the Near East, and transatlantic voyagers brought back not only tomatoes, peppers and potatoes but sweetcorn, marrows and climbing beans. It is nearly always possible, as the plants take shape, to picture their wild beginnings.

What, then, of lettuce? Where, in today's fragile and multicoloured whorls of "salad" is there any clue to a wild progenitor? Never has so much lettuce been grown, worldwide, in so many shapes and colours, or such study bestowed on the genes of a single vegetable.

The basic cultivated lettuce, Lactuca sativa, was selectively bred from a branching plant almost two metres tall, clasping small and bitter leaves to guide every raindrop down its stem. This is Lactuca serriola, "prickly lettuce", wild native of the Mediterranean and the Near East. It also seeds itself freely in corners of waste ground at Dublin Port, along with other alien species brought in with cargoes of grain and fodder. Its seeds, ground for an edible oil, were what earned the plant its portrait in ancient Egyptian tombs.

The Greeks seem to have begun the selection that reduced this lanky weed to more compact, incurving rosettes of leaves. They and the Romans are credited with the cos lettuce (Kos is a Greek island), the upright form with long, coarse leaves that Americans know as romaine.

As selection continued and spread north, the cultivated lettuce became a cool season annual and took on the rounded form, with loosely-packed, velvety leaves, known as butterhead, the "European" lettuce. In the East, the staple lettuce of China has a thick and succulent central stem, very munchable or excellent sliced in stir-fries (Western seed catalogues call it "celtuce", another American coinage).

The densely solid crisphead or "iceberg" lettuce, all crunch but little chlorophyll and still less flavour or nourishment, was first developed in America in 1920, chiefly to survive the transport from California to the eastern states. It still accounts for some three-quarters of lettuce produced in the US, much of it supplied to fast-food chains in refrigerated, pre-chopped packages.

In the later 20th century, iceberg came to dominate the supermarket shelves of Ireland and Britain. It took the "foodie" revolution, celebrity chefs and the advent of pre-packed, shredded supermarket lettuce to popularise the fifth big group of lettuce cultivars, the loose-leaf heads, in all their hectic colours and decorative frills and serrations - lollo rosso, red oak leaf and a thousand other evocative names.

These have often been bred using genes and pigments - carotenoids and anthocyanins - from neglected "heirloom" cultivars, some from as far afield as Turkey and Afghanistan. "The proliferation of form and colour existing in lettuce germplasm is quite astounding," wrote one American research team. "In a recent planting of more than 400 foreign lettuce cultivars, we found lines with leaves that ranged from dark green to light green, from deep crimson to light pink, as well as yellows and golds, and even blue teal. One line had plants with red rhubarb-like stems, another had plants that resembled balls of frilly green lace . . ."

There are, it might be thought, quite enough kinds of lettuce now, not just in form and colour but bred to make a "harvest window" of every week of the year, in every kind of climate, in almost every corner of the world.

But the susceptibility of fast-grown, heavily-watered, highly-nourished lettuce to the assault of rots, moulds and mildews will continue the breeders' quest for ever-more-resistant cultivars. GM, no doubt, will want to take short-cuts.

To these traditional hazards, fended off by toxic fungicide sprays, have been added new risks for consumers. In Ireland, Teagasc shares the EU's concern to cut down the nitrate content of lettuce, concentrated in the leaves by artificial fertiliser, and to reduce the risk of picking up cryptosporidium on lettuce watered from farm-polluted sources.

Few people these days dare to eat lettuce abroad. At home, more and more will want to grow their own, as organically as possible. Which one to choose? As a random recommendation, my current butterhead favourite is Mikola, with just enough of a blush to the leaves to be in fashion.