They travelled from Down Under, tiny stowaway seeds that turned the river banks around Scottish Borders woollen mills into a blaze of springtime colour.

Tangled in fleece shorn from sheep 10,000 miles away and washed into the waterways alongside the busy mills, the Aussie and Kiwi incomers took root, creating little corners of Antipodean colour in the most unexpected places.

Alongside Scottish bluebells, buttercups and primroses, sprouted glamorous aliens with names like pigface and Pirri-pirri bur.

With its spiky red exotic looking flower, the burr - known in Australia as bidgee-widgee - made itself at home, muscling in on native species and putting down very troublesome roots.

The story of how Australian and New Zealand plants came to pop up along the banks of the Tweed is being told in a new artistic work at the Royal Botanic Garden Edinburgh.

As well as exploring their journey to Scotland, internationally-renowned artist Keg de Souza’s three-part work, Shipping Roots, looks at the impact of colonial Britain and how the movement of plants to supply the Empire’s needs disrupted native species, landscapes and lives.

Developed using material from the RBGE archives – including some collected a century ago by an amateur botanist who became fascinated by the unusual plants growing by the Tweed – it has now prompted further research into the Australian and New Zealand species which once carpeted parts of the Borders.

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Although the archive specimens collected in the 1900s by enthusiast Ida Hayward show a mix of exotic specimens – such as karkalla or ‘pigface’, a bright pink daisy-like plant with sunshine yellow centre – some plants survived just a season while others are thought to have been lost to modern farming methods and pesticides.

A group of RBGE experts is now planning to follow Ida’s footsteps to see if any stragglers might remain.

The pirri-pirri bur, however, not only survived but went on to travel further afield, as far away as Lindisfarne in Northumbria and on Aberdeenshire beaches.

And having made its way from the port at Berwick, where the imported fleeces were unloaded, and from Borders mills where seeds contained within wool waste known as ‘shoddy’, was inadvertently flushed away, the dense, shrubby plant now poses a major risk to the Holy Island’s complex dune system.

The shrub, which squeezes out native plants, has also turned up hundreds of miles north in sand dunes at Foveran and Balmedie.

The art exhibition also examines the devastation caused by American prickly pear (Opuntia) in India and Australia, which was shipped by colonial Britain as a habitat for cochineal insects to establish lucrative dye industries and to produce the rich red shade of British military uniforms.

The cactus plants were also used by the British settlers as a prickly fence to keep native people off stolen land, and quickly grew out of control - entire farms in Australia were consumed by prickly pears, a problem that required the introduction of another non-native species, a cactus eating moth, to fix.

While the East India Company’s cochineal ventures was fraught with problems, including the wrong species of insect being introduced leading to a lower quality dye for which there was no market.

The introduction of the plants in both locations was a spectacular failure, leaving lasting impacts on the land and landscape.

The exhibition also spotlights the transport of fast-growing Australian eucalyptus from Aboriginal land, where it is culturally significant, to new forest around the world.

However, the tree’s high oil content has contributed to raging forest fires, while its rapid growth interferes with water tables.

Artist Keg de Souza, who has Goan ancestry and now lives in Sydney, said she was surprised during her research of RBGE’s archives to find so many Australian plants had been collected in the Borders area.

“Karkalla is an amazing plant that grows along the seashore in Australia, with beautiful pink flowers. It was amazing to find that it was growing in Scotland, where the climate is so different,” she added.

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Specimens were collected by Ida Hayward, whose uncles owned the Borders woollen mills of Messrs. Sanderson. One, William Sanderson, realised seeds brought from imported wool had gone on to germinate on the banks of the Tweed.

In her study of the alien flora, Hayward noted that the seeds had survived the boiling vats of water used to wash fleeces to go on to take root in the outdoors.

“The number of adventitious plants on the Tweedside is great, and the problems of their occurrence in such an unusual station interesting,” she wrote. “Many may become permanent members of our flora, but the great mass are purely ephemeral.”

Describing them as ‘nurse- lings of another sky’, she pointed out that the rigours of a Scottish winter and northern spring might kill many while others succumbed due to floods which washed away the soil and plant.

Emma Nicolson, Head of Creative Programmes at RBGE, said there is now a search for signs of any remaining plants.

“Our archives show there was once a huge number: the specimens we have range from 1880 to 1960 which would coincide with the peak of the woollen mill activity in the Borders.

“They include tiny little grasses and daisies. Some plants that arrived in the fleeces took hold, others didn’t. While the changes in agriculture in the 1960s and more insecticides meant there were fewer wildflowers.

“This exhibition has sparked interest among some of our botanists to see if they can find any of these plants still in these locations.”

Shipping Roots at Inverleith House runs from Friday, March 24 to Sunday, August 27.