Bracken's fern grip on our countryside unshakable for now

ANOTHER LIFE:EVEN AS THEY DRIP along the waysides of the west, the springing forms and vivid greens of ferns can offer exceptional beauty.

The royal bog fern, Osmunda regalis, has attained a regal magnificence beside my overgrown pond, wearing its raindrops like diamonds. A wild lady fern nearby is a fine emerald fountain of fronds.

Of all the great Irish fern family, however, bracken finds its beauty best in death, painting glowing colours across the hills in autumn.

In July, at its peak of growth, Pteridium aquilinum can be a pushy brute of a weed.

Originally a woodland plant, it muffles the clearings of old western oak woods and invades the margins of green fields and pastures, sometimes right down to the sea. In the Tiger years, when many small farmers neglected their calling for the lure of builders’ pay, bracken sneaked in to smother once-verdant sheep pastures. On my own unruly acre it presses its fronds through the hedge and springs up, stem by stem, within.

Pulling bracken by hand gives a quite false satisfaction: each stem is merely hoisted from a network of deep black rhizomes. This can give a single plant an indefinite spread, sometimes filling a whole field.

A hungry badger may rarely burrow down that far for a carbohydrate feed (as deep as 1.2 metres, I am told), but it was the trampling of cattle and horses, and collection of fern for their bedding, that once helped control it on the hills.

The cattle have gone, sheep have eaten the heather, and bracken continues to invade by up to 3 per cent a year. In a study of its spread in Ireland the environmental scientist Fiona Farrell offered an estimate that for every two hectares of farming land lost to forestry or urban development, up to a hectare is being lost to bracken.

Scattered patches of the fern offer cover to field mice and shrews and food for many insects. But, thriving in the rains of a changing climate, its often impenetrable advance is now a problem. Ireland and Britain are among several countries that appealed, unsuccessfully, against a new EU ban on the use of asulam, the mostly effective herbicide in bracken control. The ban came from the EU standing committee on the food chain and animal health, worried about the chemical’s safety when used on spinach and other edible crops. It will be withdrawn from sale by the end of the year and prohibited from use after that.

Some of the strongest protest came from the crofters of Scotland, blaming carpets of dead, dry bracken for fuelling wildfires that have swept across the hills in spring. But the fern’s bad reputation goes beyond land-swallowing and fire-raising into threats to public health.

Hill cattle may indeed have trampled bracken, but eating too much of it could give them cancers, sometimes fatally. Concerns about the human impact surfaced in north Wales in 1990, when Aberystwyth University scientists suggested that bracken’s contamination of local water supplies and cow’s milk could be causing gastric cancer. Japan, where unfolding bracken fiddleheads are a popular wild vegetable, has the highest rates of this cancer in the world.

More recently a Danish scientist (Lars Holm Rasmussen, 2003) found extremely high levels of the known bracken carcinogen, ptaquiloside, in Danish and Swedish farm and village wells.

This toxin is easily leached from the fronds of the fern, especially on sandy soils, and Rasmussen thinks it could explain concentrations of gastric and oesophageal cancer in many parts of the world.

Warned of the danger of even inhaling bracken spores in autumn, many UK ramblers’ groups now prefer to walk around it; some even carry face masks. But bracken stands are also notorious as a habitat for the sheep tick, Ixodes ricinus, and this can carry a bacterium causing Lyme disease.

Named for the Connecticut town where it was first described in the 1970s, this illness is now on the increase in these islands, typically causing heart problems, arthritis and chronic fatigue. (For more see ticktalkireland.org.)

The return of Ireland’s small farmers to a closer husbandry of land may, perhaps, bring some check to bracken. But even without the EU ban, asulam – selective, systemic and the preferred choice for helicopter spraying – was never a cheap chemical. Unlike Scotland, which pays farmers to control the spread of bracken on species-rich moorland and heath, Ireland has no such subsidy and is unlikely to start one now.

Biological controls have been explored, and one may eventually arrive, but choosing the right moth and caterpillar is a lengthy and delicate affair. Until then, Pteridium aquilinum, the world’s most ubiquitous fern, seems likely to shroud more and more hectares of our wilder countryside.

Eye on nature

Our female blackbird seems to be anting. I saw her squat down on the edge of the lawn with her wings open flat at a spot where there are ants. After a while she moved across the lawn and preened herself for some time. Is it to kill parasites?

Michael O’Malley, Lucan, Co Dublin

The ants spray formic acid on the feathers, which kills some parasites.

Recently, in the middle of Ballsbridge, I watched a fox and cub play on the banks of the Dodder. Farther along a heron stalked some prey among the reeds.

Rita Gallagher, Sandymount, Dublin

I saw a curious animal in our garden. It was bigger than a cat, a rich mid-brown in colour, with a bushy tail. It scaled a metre-high wall without apparent effort.

Creeda Fitzgibbon, Tuosist, Co Kerry

It was a pine marten, cat crann in Irish and an excellent climber.

On the shore of Lough Ree I heard the cry of an eagle. My husband saw an enormous eagle sitting in a dead tree. It had a tag on its wing with a D on it. We think it was a juvenile white-tailed eagle.

Cathy Mac Aleavey, Rathfarnham, Dublin

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo, or email viney@anu.ie. Please include a postal address.