In 1822, an exceptionally loud pair of trousers helped to launch a fashion revolution. Scotland’s celebrity author Sir Walter Scott created a sensation when he wore woollen trousers in a black-and-white check to welcome King George IV to Edinburgh – the first visit by a British monarch in more than a century. Although the design, dubbed the “shepherds’ tartan”, was a recent invention, Scott and his friends in the Celtic Club of Edinburgh were convinced that they were reviving the garb of ancient Highland chieftains. After the king himself donned a kilt, demand for tartans and tweeds rocketed, forcing Scotland’s woollen mills to import fleeces from around the world. What they didn’t foresee was that with the wool would come a flood of exotic stowaways eager to put down roots in the Scottish countryside.
THE stark, barren hills of Scotland are famous for their hardy sheep. Even so, when Sir Walter Scott made tweeds and tartans the most fashionable fabrics of his day, home-grown fleeces couldn’t satisfy demand. If Scotland’s woollen mills were to cash in on the boom in Celtic kitsch, they would have to look elsewhere for their wool. Soon, fleeces from all over the world were flooding into Britain.
Tonnes and tonnes of foreign wool made its way to Galashiels in the Scottish Borders region. The town was already one of the country’s leading industrial weaving centres. And when the railway arrived in 1849, transport costs were halved, further boosting the influx of imported wool.
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At first, in the 1830s, Galashiels imported German lambswool to produce fine tartans for dresses, but imports from continental Europe were soon supplemented by Australian merino wool, which was finer and silkier than anything grown by British sheep. Other British colonies – the Cape, Eastern Africa, the Falkland Islands and later New Zealand – all sent shiploads of wool to the Border mills. South America too was a rich source, with Argentina, Chile, Peru and Bolivia producing some of the world’s finest fleeces. Even wool from the Siberian steppes and the Indian plains, and from Abyssinia, Persia and Afghanistan, found its way to Galashiels.
The town of Galashiels lies on the Gala river, near its confluence with the mighty river Tweed. By the 1860s, naturalists had begun to notice something odd about the vegetation along the rivers’ banks. Plants from all over the world were popping up downstream from the woollen mills. By the turn of the 20th century, when 35-year-old Ida Hayward (pictured left) set out to investigate, the tally stood at 89 species.
Hayward was a recent arrival too. She and her widowed mother had moved from southern England to Galashiels, where her uncles were prominent tweed manufacturers. One uncle suggested his niece might like to document the curious phenomenon. From 1907 to 1917, with her dog Logie, she walked the rivers over and over again, collecting the strange and often ephemeral specimens she found. Every year something new would appear, while other species disappeared. Her unique collection of specimens was identified with the help of Oxford botanist George Claridge Druce and Swiss taxonomist Albert Thellung, and is preserved in Edinburgh’s Royal Botanic Garden.
Hayward’s findings, published as The Adventive Flora of Tweedside in 1919, were astonishing. She had discovered a total of 348 species of alien plants from all over the world living along the Gala and Tweed. Incomers established themselves along the river shingle, or in the town itself, where woollen mill waste or “shoddy” was used as garden fertiliser. All 348 species had travelled as dormant seeds buried in wool, and then survived the mills’ draconian cleaning regime: alkali and acid baths, followed by dry heat and crushing through heavy steam rollers.
Some plants had journeyed halfway round the world and back again. One legume sporting hefty burrs, a species of medick in the genus Medicago, had travelled first with colonists and their merino sheep from its native haunts in southern Europe to the Argentinian pampas and later to the grasslands of Australia. Now, its descendants had returned to the Old World, lodged in wool shipped to Galashiels from both continents.
“Some plants journeyed halfway round the world and back again”
Nearly half of the incomers originated in Europe and the Near East, but natives of Australia, South Africa and the Americas were also well represented. One coloniser with attractive yellow blooms established itself along almost 15 kilometres of river bank; it turned out to be Bidens pilosa, a semi-tropical plant from South America.
Hayward found species that were new to Europe, says botanist Rod Corner, who grew up near Galashiels and is now a recorder in the region for the Botanical Society of the British Isles. Some were even new to science, and one plant, a hybrid goosefoot called Chenopodium x Haywardiae, was named after her. The plant’s parents, from Argentina and India, seem to have met at Galashiels.
For a time, it looked as though the woollen industry of Galashiels “might have been designed for the specific purpose of introducing troublesome plants into Scotland, so efficiently did it gather, concentrate and propagate aliens along the banks of the Tweed”, says Jonathan Silvertown, a plant ecologist at the UK’s Open University. Yet the flowering of a global flora in Tweeddale was to be short-lived. By 1919, the town and its mills had a sewage works, and viable seeds from the mills ceased to flow into the rivers. It soon became clear that the incomers were failing to establish self-sustaining populations.
In the 1960s and 1970s, botanists repeatedly surveyed the Gala and the Tweed and occasionally found a few survivors from the wool-aliens’ heyday. In 1990, medicks popped up briefly, germinating from buried seed released by river erosion, but none of the plants survived more than two seasons. The Galashiels wool aliens, it seems, have gone for good – with one exception.
The pirri-pirri-burr (Acaena novae-zelandiae), a native of New Zealand, has travelled down the Tweed to the North Sea and established itself along the coast, on the sand dunes of Holy Island, or Lindisfarne. Today its exceptionally prickly burrs are a hazard for walkers and sometimes lethally entangle the feathers of ground-nesting birds.
So what went wrong for the other 347 wool aliens of Galashiels? “Climate must be part of the answer,” Silvertown says. “The cooler the climate, the harder it is for aliens,” especially in the wild, where they have to compete with established natives. Yet even in the Mediterranean, alien species have come and gone, exhibiting the same “fugitive character” seen in Galashiels.
Decades before Hayward began her investigations, the great entrepôt of Montpellier on the south coast of France boasted an even richer alien flora. In the 1890s, when Thellung began totting up all the aliens that had ever sprung up near Montpellier’s Port Juvénal, he soon realised he had taken on a monumental task: 800 alien species – more than half of them probably wool aliens – had at one time or another tried to colonise their adopted land. The Montpellier total trumped Galashiels because more warmth-loving Mediterranean species were able to germinate there, but in terms of the global range of its botanical exotica, Scotland won hands down. Even in mild Montpellier, the alien invasion proved short-lived. After 1880, wool was no longer processed near Montpellier, and by 1905 Thellung could find only 10 perennials precariously hanging on.
The fate of the wool aliens of Galashiels and Montpellier points to the solution of an abiding ecological mystery: why is North America overrun with European plants, many of which have become serious pests, while Europe suffers from far fewer troublesome invaders? Although Europe is awash with foreign plants, many of them garden ornamentals, only a small proportion have become established in the wild, making up no more than 5 per cent or so of species. In parts of North America, such as Florida and Ontario, 30 per cent of species growing in the wild are aliens. Why such a big difference?
The answer, says Silvertown, must lie in the transplantation of whole ecosystems by the European colonists. In trying to recreate their native pastures, the settlers introduced a suite of grassland plants from Europe. The invasive weeds are simply their less palatable travelling companions, freed from the constraints that kept them in check in their native lands. The take-home message, Silvertown says, is that just as with people, it is impossible to predict from a plant’s domestic demeanour quite how it will behave when abroad.