'Tis the season to see holly

I love the bright glow of the small country towns these dark afternoons, each one a setting for that ESB commercial about the much-loved son coming home from the station. But the tangle of cut holly, for sale under somebody's arch, gives me a small lurch of misgiving. Where did it come from? Does anybody care? Shall I find some favourite tree, out on the hill roads, reduced to a stump?

Conservationist paranoia: it hasn't happened yet. Why not suppose, instead, that holly harvesters have made their rounds of well-loved, well-respected trees, trimming each in its turn once every three or four years? The female trees, the ones with berries (but few enough this year), take 40 years to reach their peak of fruitfulness, but then they'll carry on for at least another century, maybe more. Pollarded ones may thrive for three centuries, says Charles Nelson's tree book.

There is a special, stubborn elegance about many of Ireland's wild hollies, growing in difficult, inhospitable places. The rippling, dark-green leaves of the Burren's hollies, says Nelson, seem finer than those of other places. They are "edged with a pale band of translucent gold and are remarkably sinuous, their rapier-sharp thorns alternately pointing in opposite directions. Set a leaf on a flat rock and it stands on tiptoe like some Gothick beast . . . " The Burren was also where Richard Mabey once found "a prostrate, golden-leaved tree sprawling across a rock" - one source, perhaps, of the variegation.

My own hollies of character - attitude, you might say - are those surviving in rocky niches on Connacht's mountainsides, leaning out above waterfalls, where the sheep can't reach, or wound around rocks, bark bleached to silver.

They hold on, too, in dry-stone walls of farmland, trunks bare up to the browse-line of cattle. The sight of a heifer eating holly is memorable: the way the animal tries the leaves two or three ways in its mouth, seeking the least painful fit before it bites. There's no great hardship, otherwise, in eating holly: its waxy leaves are exceptionally nutritious. Indeed, whole woods of holly were planted in medieval Britain, specifically as winter fodder for sheep and cattle.

It seems it was wrong to believe - as certainly I used to - that the prickles on holly leaves evolved as a defence against such browsing, leaving the tree to grow its plain-edged leaves higher up. Spiny leaves evolved to cope with drought (as did waxy coatings), and in the holly they coincide with the tree's most vigorous stages of growth. Some hollies have prickly leaves throughout; others grow spineless leaves at the top, as their annual energy declines. If the hollies of the bare Burren limestone have the prickliest, most twisted leaves, it is probably because they are growing in some of the driest conditions in Ireland.

The tree's more natural habitat is in an oakwood, where it grows as an under-storey and uses the light in the months when oaks are bare. It is what we should see in western woods now choked with rhododendron, or grazed past all redemption by invading sheep and cattle. But more hollies survive within hedgerows, planted there with hawthorn and ash, or arriving by courtesy of birds. It is our lazy custom, after Christmas, to wedge the redundant twigs into the hedge outside the door, where blackbirds strip them. Our reward has been a couple of holly seedlings, inching up with painful slowness from the hedge-bank.

Ireland's hedgerow hollies, Christmas notwithstanding, are probably bushier than ever. One thinks of all the uses they were put to in the past - if not for the chariot shafts of medieval Ireland, then for anything around the farm that needed dense, tough wood: tool handles, pegs in chimneys.

Any time that fuel was scarce (as it often was, in the crowded countryside of the early 1800s) holly was a tempting firestuff. "Holly, burn it green," sang the Celtic fire-servant, "holly burn it dry: of all trees whatsoever, the critically best is holly." Utility protected the tree through the ages; so did the bad luck inseparable from cutting one down.

Among the birds, the mistle thrush is especially glad of holly. It will sometimes choose a well-berried tree and defend it through the winter as its private larder. But why should it have to do without the berries it was named for? The only records of Irish mistletoe I have come across are both from the North: on an apple tree at Cave Hill some 60 years ago, and on a tree on the Lagan towpath in 1982.

On the face of it, there should be mistletoe in Ireland. Its heartland in the UK is the mild, humid border country of England and Wales, around the Severn estuary. One-third of the apple trees in the Hereford orchards sprout clumps of its wishbone leaves, and in places it is nurtured as a cash crop (most of that sold at Christmas actually comes from the cider-apple orchards of northern France).

But apple trees are not at all essential. As Richard Mabey records in his Flora Britannica, the parasitic mistletoe is moving to new hosts as the old orchards are grubbed out and birds wipe the sticky seeds from their bills on the soft-barked trees of parks and gardens. Walnut, laburnum, almond, weeping ash are all sprouting mistletoe now, and at the Berkshire College of Agriculture the crop is harvested from old lime trees by shooting it down with a shotgun.

Mistletoe can be propagated with perfect success by implanting the seeds under the bark of poplars and apples. In the early 19th century, says Mabey, one could buy small trees already sporting mistletoe bushes - just the sort of thing, one might have thought, to appeal to the Irish Big House. Perhaps it did, and has been lost with all the old, mossy orchards that once grew behind the walls.

At this 20th Christmas of "Another Life", a special greeting to my readers.