A creeping animus against ivy is taking hold

Another Life: The young ash tree outside the window is as perfect as they grow: a regular, multi-branched candelabra, its vertical twigs tufted with the first green flames of spring.

Late into leaf and first to lose them, it is the one tree in the garden to hold its symmetry in the sculpting sea wind.

But nature makes no promises to trees, about perfection, symmetry or anything else. In much of the world, trees are climbing frames for other plants. In tropical forests, they are climbed and throttled by lianas and let out in flats to bromeliads and giant ferns. In the southern US they are draped with trailing Spanish moss. In Killarney, old oaks are hanging gardens for the more modest mosses, ferns and lichens of Ireland.

Over much of the island's interior, however, and notably in the east, what climbs trees is common ivy, Hedera helix - or rather, as a new Enfo wildlife information pamphlet insists, ivy is what "infests" them.

Indeed, the words "infest" and "infestation" (like rats, nits and cockroaches) haunt a good deal of the pamphlet, along with advice on ways to get rid of ivy, at least from trees and hedgerows.

Enfo, based in Dublin's St Andrew Street, is the Government's Environmental Information Service and its leaflets are source material for inquiring young minds and school nature projects.

The new one, Ivy and Trees was commissioned by Minister Dick Roche from Prof Risteard Mulcahy, who has made a crusade against ivy in trees a typically vigorous preoccupation since his retirement from heart surgery (he is now in his 80s).

He first began lobbying ministers on the issue in the 1970s, and his book For Love of Trees, published 10 years ago, made a most persuasive case against ivy's disfigurement of the countryside's roadside and specimen trees. Now, as the professor told Roche, the Irish Tree Society "has accepted as a matter of policy that the excessive growth of ivy on our trees should be discouraged".

His pamphlet does not ignore the counter-argument that has sustained this controversy for many years - that ivy is valuable to wildlife as nesting cover for birds and a late nectar source for insects. But he reasons that "if every tree in Ireland were free of ivy, there would still be an ample amount of the plant to cater for all the wildlife in the country".

His animus towards it is part aesthetic, part the forester's concern that trees should grow as tall and straight as they can. "When the growth reaches towards the top of the tree," he writes, "it damages the lateral branches and eventually distorts the canopy, thus altering the attractive natural shape of our hardwoods."

He is also convinced that, while ivy draws no nourishment from trunk or branches, it competes for water and nutrients at ground level.

A few strands of ivy, traversing tree-trunk or wall, offer one of nature's most enchanting plant designs. But while, in the west of Ireland, the shrouding habit of ivy seems organic to the landscape, its exuberant growth - I will not say "infestation" - on trees can indeed be aesthetically disturbing further east.

A recent train trip to Dublin found me struck by the way, as I put it in a previous column, "line after line of shapely trees is blotted and blurred by the wanton sprawl of Hedera helix". Most of them, indeed, were ash trees, which happens to be the Tree Society's "Tree of the Year".

Risteard Mulcahy's crusade would not seem at all out of place in the US, where "English ivy" is widely loathed as an introduced, invasive alien, creating ecosystem problems in 18 states. In the northwestern US, in particular, it grows rapidly in deciduous forests, carpeting the ground and blanketing trees in what is termed an "ivy desert" by some conservation agencies. In Irish woodlands, the alien, invasive rhododendron is battled for comparable reasons.

Why has our native ivy gone over the top in so much of Ireland in recent decades - if this, indeed, is what has happened? Prof Mulcahy is inclined to blame the lack of goats, which used to browse on the young climbing shoots. But that suggests that many of our ancient forests were well-festooned with ivy. Perhaps they were. In his History of the Countryside (1986), Oliver Rackham wrote: "On an island in a boggy lough in Co Offaly is an extraordinary wood of great ancient oaks, hung with ancient ivies (one ivy trunk is thicker than a fat man)." Ivy has been climbing trees for a very long time, but this life-sharing does not amount to one of nature's mutualisms: the tree gets nothing out of it, and the ivy, once thickly aloft, probably does distort the progress of its growth.

I, too, would prefer to see more of Leinster's roadside trees relieved of their dark shrouds - but this for what, in the end, are largely aesthetic fancies that should really not be a guide in education about nature.