TURN AND RUN

SOMETIMES, working bare handed in the garden, I am consciously appreciative of the generally benign character of Irish nature, at least so far as people are concerned.

I can tunnel into the soil, pursuing roots of couch grass, without fear of engaging with, say, a deadly centipede I can snatch up a pile of dead leaves without wondering if a fer-de-lance might be sheltering within. Ants, midges and stinging nettles may raise a few minor bumps, but the worst injury nature does me, day today, is to drive tiny thorns into my finger tips, for domestic excavation with a needle and magnifying glass.

We have wasps, but no hornets mosquitoes, but no malaria (both could change, as we warm up). When the final wolf was dispatched (near Mount Leinster, in 1786), that wiped out the last mammal with even the hint of a snarl.

How hazardous, by comparison, is rural America Granted. you have to go looking for trouble, but what potential there is for it in the woods and swamps and. deserts (and also, perhaps, in herbaceous borders in some adjoining gardens!) Copperheads, coral snakes and rattlers, black widows and scorpions, gila monsters, skunks and porcupines.

Poison ivy we've heard of, but what of America's poison sumac and the dreaded manchineel tree, so caustic is its sap that even rain drips burn! By an irony, its nearest equivalent in Ireland is a plant man himself has released into the wild.

Heracleum mantegazzanium, the giant hogweed, is a beautiful statuesque plant, sometimes reaching an astonishing five metres tall, which grows naturally along the streams and forest margins among the mountains of the Caucasus, in Russia. There, presumably, the locals know that its juicy sap, secreted through bristles along the stem and leaves and pouring out whenever the plant is broken, is highly toxic to human skin.

The sap's active ingredient, called furocoumarin, damages the skin's capacity to screen out ultraviolet rays from the sun. The effect is permanent, so that a serious dermatitis, with rashes, blistering and swelling of the skin, can occur even years afterwards, whenever bright, mid-summer sun reaches the damaged tissue.

Children like to play with the great, hollow stems of the hogweed, using them as pea shooters or "telescopes", and the severe burns they can suffer have sometimes needed skin grafts. At Loughlinstown, Co Dublin, children playing in the Shanganagh River have learned not to dry themselves with the big leaves of hogweed growing on the banks, but the local hospital still regularly treats burns from the sap in the summer months.

Heracleum mantegazzanium was introduced to these islands towards the end of the last century as a decorative plant for parks and Big House demesnes. It is a biennial which flowers in its second year, dying away after it has seeded, but each magnificent head of white flowers produces up to 20,000 seeds. These travel particularly well in water and can remain viable for 15 years. So giant hogweed both spreads its thickets locally, by dropped and wind blown seeds, and starts new stands on river banks downstream.

THE first thorough report on the spread of the plant was published in 1989 by botanist Dr Michael Wyse Jackson (now with the OPW). His survey, in the bulletin of the Irish Biogeographical Society, quoted from a song by the rock group Genesis. "Turn and run Nothing can stop them Around every river and canal their power is growing.

There followed 10 pages of recorded sites of hogweed in 25 of Ireland's counties.

In 1994 John Lucey, monitoring water quality for the Environmental Protection Agency, added new records from southern rivers. On the Newport River in Co Tipperary, where Robert Lloyd Praeger found the hogweed almost 60 years ago, it has now colonised the roadside "a hazard to pedestrians, as well as motorists".

The recent, updated edition of Stewart & Corry's classic Flora Of The North East Of Ireland, records the plant as "local, but abundant where found and often extending along several miles of river banks."

Together with the health hazards and problems for anglers, Hmantegazzanium can be a menace to stability of river banks themselves much to the concern of, the fisheries boards. Dense stands of the plant kill off everything else in their shade, so that in winter, when the thicket dies down, the earth is left bare for erosion.

Spot spraying of hog weed with glyphosate (Roundup) early in the season is the recommended control, but this needs to go hand in hand with the planting of new soil binding vegetation. Roundup can also harm fish, so the local? fisheries board does like to be consulted first.

Biological methods might seem preferable, but hacking hogweed down a dangerous pursuit merely makes it try harder, and, digging it up usually leaves a viable root behind. A third way is to let the plant think it has produced its seed, then seize its seed head before they can do their scattering, a stratagem needing a step ladder and a nice sense of timing.,

Better still, if something would eat it and come to no harm. John Lucey quotes research suggesting that cattle or pigs "relish the plant" (perhaps as young shoots). The Irish name, feabhran capaill, on the other hand, probably has less to do with horses than with the hogweed's impressive size.