Thriving on the scattered showers

If there has to be a summer in Ireland (I would just as soon skip straight from spring to autumn), let it be of this old-fashioned, Irish kind: cool, showery and soft, with intermittent sun - in a word, fern-friendly. In the dry-stone wall across the road, the male fern, the scaly male fern and the lady ferns, the polypody and the maidenhair spleenwort have never looked in better nick.

This is the climate, after all, that shapes some of our lushest and most interesting vegetation and keeps us in touch with our natural ecological neighbours in the Atlantic. On the west coast, especially, we should feel part not only of a Celtic fringe, but a botanical one, an oceanic continuum stretching south all the way to the Macaronesian islands off the north-west coast of Africa - Madeira, the Azores and Canaries. In the cool, misty laurel and heather forests that cling to the steep mountain slopes of those islands are the richest fern habitats of the temperate zone. And among their plants are several which flourish quite as happily in moist and equable niches along Ireland's western coast. Fern spores, fine as dust in the wind, redistributed many "sub-tropical" species northwards after the Ice Age, but they could only take root and survive where conditions were exactly right.

One of the best-known is the Killarney fern, Trichomanes speciosum, with delicate, finely-cut, translucent fronds a foot or more long. It seeks out damp, dark situations in the gorges of waterfalls or under overhanging rocks. It used to be at least "frequent" in the south-west of Ireland, but plant-collectors during the Victorian fern craze uprooted large quantities to sell to gardeners and tourists. This wiped it out at many sites (including the Powerscourt waterfall, in Co Wicklow, where it was first found) and today it is a very rare and protected plant, growing in scattered splashy spots from Kerry to Donegal and in Fermanagh.

Two more rare Macaronesian species are small but exquisite filmy ferns that might almost be mistaken for large mosses (ferns come in an incredible range of shapes and sizes, some as small and fine as grass, others large and sturdy as trees). Both have Hymenophyllum in their name and are supposed to grow in habitats that stay wet, shady and humid all the year. In the Killarney woods they ripple over rocks in great sheets of greenery, and infiltrate the saturated hummocks of mosses, but they can also survive on exposed mountain slopes beside the sea - on Achill, for example, and Tully Mountain in Connemara - provided they get enough overcast days in the year.

The lovely maidenhair fern, Adiantum capillus-veneris, a southern European but not especially Macaronesian species, roots its black stems inside the scailps, or fissures of the limestone pavements of the Burren and Aran. It enjoys a calm life in stable temperatures, springing up in Europe in wells and fountains, or even lighted caves (in Ailwee cave, lit up for tourists, they scrub the young plants off the rock with a toothbrush).

For sheer ecological precision, however, it would hard to beat sea spleenwort, Asplenium marinum, a glossy little bush of a fern abundant on the most exposed sea-cliffs of the west. It tucks itself into the dark, still niches of undercut rock or arches, and welcomes the drift of salt spray on to its waxy leaves. The spray is essential, since it bathes the rock in the ocean's stored winter warmth and keeps all threat of frost at bay. Sea spleenwort also finds a home in the deep Burren scailps around Poll Salach and Black Head, within splashing distance of the breakers, and grows there to remarkable size. "It is certainly a wonderful sight in the middle of January," wrote Charles Nelson in his Burren book, "the majestic, dark green fronds of Asplenium marinum, dripping wet with rain and spray and just reaching the pavement surface, highlighted by the brief rays of the low sun against the water-black limestone." (Dr Nelson, like me, prefers the more dramatic seasons).

Humid Atlantic air supports the exuberance of Ireland's tallest, most stately fern, Osmunda regalis, and holds it close to the coast, growing slowly in peaty ditches and at the margins of bogs. The "royal fern" reaches a great size, sometimes sending up fronds headhigh, and its clumps of rhizomes can reach a metre or more across, marking them as ancient, like an old oak tree, and worthy of respect. Unfortunately, Osmunda has been a common casualty of land drainage schemes in the west and seems doomed to diminish further in the coming century: such a pity, after 280 million years.

In many old Atlantic oakwoods, overgrazing has wiped out the diversity of ferns and encouraged just one of them - bracken (now coming up to its release of toxic spores: do not wade through it). In an experiment near Killarney, deer and sheep were shut out from a section of woodland. This brought not only a regeneration of trees but a thinning of the bracken canopy and the return of many forest fern species.

All over the sheep-degraded uplands of the west the deep ravines, with their waterfalls and rushing, rock-walled gorges, have become the last refuge of mountain ferns. Below the leaning oaks, rowans and hollies are the hard fern, the lady fern, the bucklers - even, perhaps, the hay-scented buckler, Dryopteris aemula, which has its main headquarters in the Azores. On fallen, rotting branches cloaked in moss, polpody ferns sprout in a brave imitation of a mist-forest.

Ireland may not have as many ferns as Britain, or as many precious rarities (though more than I have named). But the species we do have are often more luxuriant, or grow in lively and interesting ways. Yet in the general estimation, ferns seem just to merge into our everyday rural "greenery". How many of us, proud of putting a name to quite unusual wayside flowers, could name the first two or three different ferns encountered along a ditch or a dry-stone wall?

They are all beautiful: one can see why the Victorians became so keen on them. If the holiday weather stays gloomy, try the kids with pressing ferns and flowers for mounting on greeting cards; I have a soft spot for these. A book with all the useful colour photographs for identification is Grasses, Ferns, Mosses And Lichens, by Roger Phillips, published by Pan.

Eye On Nature

I found a variegated arabis plant on the Devil's Bit Mountain close to the summit. It had a small, green caterpillar, about three-quarters of an inch long, with a black head, on a leaf. When I touched the caterpillar it disappeared, and I found it under a stone approximately a foot away from the plant. I again touched the caterpillar which in the twinkling of my eye had gone under another stone again about a foot away. Any idea of its nature?

Ned Meagher, Templemore, Co Tipperary

It is difficult to identify the caterpillar without more detail; it could be that of the dingy skipper butterfly. However, I have failed to find any record of a jumping caterpillar.

The crows and magpies are all opportunistic feeders and often eat all kinds of berries. Wood pigeons eat berries as a matter of course although they prefer grain.

My wife and I both saw at different times what we thought were strange, white creatures, longer than dragonflies, flying in the garden and descending almost vertically when landing. Finally, after much stalking and pouncing, we captured one and found them to be small, tattered pieces of newspaper, and then it dawned on me what had happened. Two days previously I had united two colonies of honey bees in one hive, and had used a sheet of newspaper as a temporary barrier between them. The "strange creatures" were the shreds of paper which the bees were cleaning out of the hive and carrying away. Bosco Bonar, Dunfanaghy, Co Donegal

Edited by Michael Viney, who welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo