Forging nature's signature

In shady corners of the acre, a haze of starry pink flowers rewards me for years of positive discrimination: whatever else has fallen to hoe or mower, the wild herb Robert has always been left to flourish along banks and hedge-bottoms. Out in the sun, bedded in the limestone chippings of the "street", brilliant mounds of flowers have the same five petals to the cup, the same elegant dissection of leaves - but all on a far more flamboyant scale and in half-a-dozen shades, from pink to a deep violet-blue. Whether as wildflowers or glamorous garden cultivars, I seem to have fallen for geraniums.

These are not, of course, the geraniums of city parks and hanging flower-baskets (which are actually Pelargoniums from South Africa), but an allied tribe of plants in the Geraniaceae, the genus of cranesbills of the European countryside. Geranus is the Greek word for crane - a reference to the beaked seedcase that sticks up when the petals have fallen.

Each year I hope to be passing by when the beaks unzip to hurl the seeds like stones from a sling; it never happens. Instead, I find fresh seedlings springing up between the chips of limestone. Used everywhere now (and spoken of, in county council idiom, as "maint'nance") this crushed quarry-rock creates a miniature Burren scree.

The bloody cranesbill Geranium sanguineum is, of course, the most vivid plant of the Burren, its fierce magenta flowers splashing the soft greys of limestone, and it is offered, without need for improvement, in garden catalogues. But it is just one of 14 cranesbills growing in Ireland, including a few garden cultivars catapulted over the wall and now naturalised here and there in the wild.

Northern Ireland, with its early tradition of cottage gardens, always has more than its share of escapes, but the real surprises are in its wild geraniums. The "Flower of Dunluce", for example, found on sand-dunes and grassy places near that craggy Co Antrim castle, turns out to be the Geranium pratense, a meadow cranesbill with gloriously big, violetblue flowers.

In the same county, hazel scrub in the Glens of Antrim shelters the only native Irish populations of the wood cranesbill, G. sylvaticum, a lovely, downy plant with purple flowers that are smaller and darker than those of G. pratense.

Garden escapes among the North's geraniums seem to have a fitful existence in the wild. A species from the French Pyrenees, the pinkflowered G. endressii, appears in vivid colonies in scrub or wasteland and then dies out again (it is also the most vigorous settler on my street). The dusky cranesbill, G. phaeum, from central Europe, has flowers of funereal purple - "Mourning Widow" is a Lancashire name for it - and plants naturalised near an old churchyard in Magherafelt may date from a fashion of planting it on graves.

Around Dublin, the introduced geraniums are not alien garden varieties but native plants in the "wrong" place. Shining cranesbill, for example, which flowers much like herb Robert but has smaller, rounded, glossy leaves, was brought to Dundrum a century ago and "spread like wildfire".

Sorting out the botany of native cranesbills and chasing up the provenance of garden sorts has added a lot to my pleasure in the plants, but also raised a few slight misgivings. The meadow cranesbill, grown from catalogue seed, is billowing beautifully around the garden pond and taking off in every direction. A Balkan, if not actually Serbian, species, G. macrorhizum, has edged out everything else for two square metres and is still spreading. The pencilled cranesbill from Italy, the little blue-cupped job from Finnish pine forests (G. bohemicum) - everything is seeding happily into the scree of limestone "maint'nance" and the sandy soils beyond.

As a gardener, I'm thrilled. As an amateur ecologist, I'm sometimes uneasy. How soon will the thousands of new Irish country gardens, stuffed with plants that are actually the wildflowers of other landscapes, begin to falsify the native flora - "forging nature's signature", as Praeger used to thunder?

But botanists will, no doubt, take escapes in their stride. They worry rather more about the mixtures of wildflower seed imported from the UK and beyond. Often sown with the best of intentions, these correspond to our native flora, and may contaminate the gene pool of native plants.

Meanwhile, Charles Nelson has produced a splendidly user-friendly pocket guide for ordinary flower-lovers - Wild Plants of The Burren and the Aran Islands (£10), published by Collins Press of Cork. He uses his own excellent photographs, each with its place and date, to identify 120 flowers, most of them widely found in these limestone landscapes.

Among the more special ones is a garden escape (or deliberate introduction), the lovely fairy foxglove, native to the Pyrenees and Alps and now colonising the cliffs above the green road on Black Head. A much older and more legitimate introduction is Babington's leek, the "garlic" of the Aran Islands, brought in centuries ago.

Almost everything else belongs, all of it beautiful. Even the turlough dandelion has charms when you read that it is "perhaps more abundant in the Burren than anywhere else in the entire world". The book has a special space on each page to write where and when you found the flower - very Victorian and a great souvenir of happy times.