Taking up the cause of conserving Irish elms

Another Life: The biggest trees of Brighton, my home town, were the majestic municipal elms, marching seawards along the lawns at the heart of the city and towering over the civic tulips and geraniums. You had to walk round their great, dark trunks - "all notched and scarred,/ Like to a warrior's destiny" as John Clare had it.

Going back there a couple of decades ago, I found many of the warriors starkly crippled by Dutch elm disease (DED), which has killed more than 25 million of the UK trees. The bare chalk hills of the South Downs did slow the spread of fungus-bearing beetles, and Brighton and Hove managed to keep many fully grown elms among its 12,000 street trees. In a new cycle of infection, however, some hundreds of them have had to be felled.

In the 30 years since the last big outbreak of DED (the Dutch identified the disease and got stuck with the name), the European family of elms has received close genetic scrutiny in the search for resistant strains. This has revealed that the so-called "English elm", Ulmus procera, planted plentifully also in Irish estates and hedgerows, is actually the product of a single clone carried abroad by the Romans, first to Spain and thence to England. The species doesn't set seed in the north, but suckers readily, and so guaranteed the Romans a supply of stakes for their grapevines.

This lack of genetic diversity helps to explain the rapid spread of the disease, but DED affected all elms. In Ireland trees sickened and died wholesale in the 1970s and after, but the post-mortem suckers of English elms still provide viable hedges in many parts of the country.

Teagasc's Dr Gerry Douglas, writing in the current issue of Crann, the tree magazine, explains that the Scolytus beetles are attracted only to trees higher than 1.5 metres, with well-developed bark in which to plant their eggs.

Dr Douglas is the latest Teagasc scientist at the Kinsealy Research Centre in Dublin to take up the cause of conserving elms for Ireland. His home town is Ardee in Co Louth, where, amazingly, 11 mature elms of two to three-metre girth are surviving in a single two-acre rectory garden. One is the tallest and fattest English elm in Ireland, listed among the island's "champion trees" by the Tree Council of Ireland; the others are smooth-leaved elms, which are also reported from the Blackwater and Bandon valleys.

With the help of Aubrey Fennell of the Tree Council of Ireland, Teagasc researchers have located 29 mature elm trees in Ireland between Louth, Meath, Carlow, Kilkenny and Donegal. Some are clearly the "wild" native wych elm, Ulmus glabra, but others fall uncertainly into a group of hybrids with English and smooth-leaved elms (now collectively regarded as Ulmus minor). Telling elms apart can get very complicated. In their purest forms, their shapes can be very different - at one extreme the lofty, upright English elm; at the other the spreading, rounded (in some cultivars, even weeping) wych elm.

The wych has a large, hairy leaf with a lop-sided base, roughly toothed and on hairy twigs; the Ulmus minor group has generally less hairy leaves and twigs, with smaller leaves on little stems or petioles. But, as the great silviculurist Herbert Edlin wrote, "most of the variations . . . can be found, or at least imagined, on one and the same tree" - even bark patterns mix in the hybrids.

What matters is finding as many healthy and genetically different survivors in as many locations as possible. Seed production and natural regeneration of all elms is erratic, so that growing from cuttings is the best way forward in conservation. At the Kinsealy research centre, more than 1,200 cuttings have been planted and some have rooted for each of the 29 trees found so far. The offspring will be cloned into hedges, with some saplings being returned to the tree owners and more planted out at field boundaries and in mixed woodlands. Some may be challenged with live fungus, in research conditions, to test if they are, in fact, resistant strains, or if their parents were just lucky in dodging DED.

Dr Douglas is naturally keen to see that some find a home around Ardee, with its remarkable rectory elms. By an irony, these have survived (so far) not just DED but the potential hazards of a housing development in the next field (the saga of concern for the trees, along with photographs, is offered at www.ardeeoldrectory.com).

Meanwhile, Dr Douglas needs to hear about every healthy wych elm or hybrid from which he can take cuttings. The Kinsealy Research Centre is at Malahide Road, Dublin 17; telephone him direct at 01-8459006 or e-mail gerry.douglas@teagasc.ie