The curse of furze, or the glory of gorse?

Another Life: It's always a great spring for whins (or furze, or gorse, depending on your birthplace). That lavish rush of gold never fails to thrill, outstandingly in Leitrim, where it's married in April to dazzling green waterways of willow and the bright blue arches of drumlin skies.

Over on the broader horizons of Kildare, Stephen Rynne, an artist-farmer, could scarcely contain his love of furze: "May I marry a girl of furze-coloured hair! Give me bouquets of it, sheaves and posies; stick it in wands for me; nail it to my mast; and hang it out of the windows should I come riding home in triumph."

Even without such ecstasies, Ulex europaeus served old Ireland well. Along with an obvious duty as a hedgerow, it was chopped and fed to cattle, burned in bakers' ovens and limekilns, and used to roof outhouses, line field drains, harrow crops, keep the haystack off the ground, clean the chimney, make hurleys and hammer handles, dye socks and Easter eggs, and as a Velcro perch for the family wash on windy hillsides. Its versatile role in the rural economy was chronicled in Furze, a little book compiled half a century ago by Dr AT Lucas, then curator of the National Museum of Ireland.

By that time, as Lucas acknowledged, furze was regarded as "little better than a troublesome weed". And while I've been admiring its current glory on local hillsides, it does seem to be gaining ground. Indeed, as the small-farm countryside loosens its grasp on marginal land, and global warming selects the shrubs that succeed in drier soils, furze, whin or gorse could make advances past all current imagining. Ulex europeaus is ranked high, after all, among the world's 100 worst weeds. Not only will it flourish in almost any land and grow muscular branches and roots, it fires out seeds - up to 6 million to the hectare - which will last in the soil for up to 30 years, making eradication a slow, difficult and costly process.

Seeds from Ireland were brought to Oregon on the American west coast in the late 1800s and covered some 25,000 acres of the state by the 1950s. A few plants were brought into Marin County in California as "a bit of ould Ireland" and ended up covering 15,000 acres. The shrub is now established down the west coast from Seattle to Santa Cruz and on the Atlantic coast from Virginia to Massachusetts.

In Australia, gorse has come to be one of those deeply-regretted introductions from Europe (as a hedge-plant, in the early 1800s). At its worst concentrations, in Tasmania and southern Victoria, its advancing thickets are costing sheep farmers millions of dollars in lost production, this despite the fact that sheep, along with goats, are among the rare browsers of the prickly growing plant. In New South Wales, as in California, gorse has come to be a major problem of national parks and reserves.

Even in Ireland, Ulex europaeus was an early introduction from the Continent - our native gorse, largely confined to the southern counties, is the dwarf Ulex galli, which makes such a sumptuous carpet when it grows among blossoming heather. But, right from its start on this island, the alien gorse of heathland Europe was controlled by its rural usefulness, as well as by a suite of co-evolving weevils, thrips, mites and moth caterpillars quite absent from the New World and Australia.

Ecologically, indeed, furze is exceptionally valuable to Irish wildlife, being also deeply appreciated by stonechats, linnets and warblers, the bees to whom it offers some of the earliest nectar in the year and the abundant spiders whose dew-covered webs are so prominent in autumn. As an aggressive invader of neglected marginal land, we could, it might be thought, do worse.

On the other hand, as ecologist John Feehan has pointed out, the shrub's short-term expansion is generally at the expense of semi-natural grassland, rich in species and of higher conservation value (as is happening, for example, on the esker slopes of Co Offaly).

"The problem with furze today," Feehan writes in his monumental Farming in Ireland, is that it has ceased to be useful. It is inconceivable that hundreds of hectares of furze would have been left to flower and grow old in the landscape of an earlier farm economy." But the way some of the countryside is going, the ultimate curb on its growth may be the developer's bulldozer.

• A postscript plea to vigilant readers: Philip Duggan, of the Wildlife Ecology Group in TCD's zoology department, needs dead stoats to study. Road kills (other people's, of course) are his only hope. His e-mail: phduggan@tcd.ie.