Pirri pirri – How a Scottish royal visit triggered an invasion

Pirri pirri – How a Scottish royal visit triggered an invasion

This is a curious tale of unforeseen consequences – how a royal visit to Scotland in the 19th century led to a plant invasion from Australia that is still being dealt with today.


In August 1822 King George IV made a royal visit to Edinburgh. It was the first by a reigning monarch in nearly two centuries.

Right: George IV in kilt by Sir David Wilkie, 1829. Left: A contemporary caricature of King George IV in kilt during his visit to Scotland in 1822. Image from “The King’s Jaunt” by John Prebble.

The flattering painting to the left (above) by David Wilkie shows him in full Scottish regalia looking in his prime. In reality he was 60 at this point and on his way to weighing 20 stone. He had a 50-inch waist. But look at those lovely bare knees. Yes, well, in reality he actually wore a pair of “pink tights” or “flesh-coloured pantaloons” and stockings to keep him warm.

Short kilt

His kilt may have been lengthened in this painting too. Scots joked about how short it was. One wag commented: “Since he is to be amongst us for so short a time, the more we see of him the better.”

Sir Walter Scott, who had the sense to wear a pair of black and white checked woollen trousers for the Edinburgh visit, organised the welcome. He was intent on promoting Scottish culture. Pipers regaled the king. Around 1200 gentlemen attended a reception, all of them encouraged to wear tartan.

An embroidered picture of Sir Walter Scott at home – in his checked woollen trousers. (Metropolitan Museum of Art, CC0, via Wikimedia Commons).

Crowds gathered to cheer the king throughout his three-week visit – with as many as one in seven Scots getting to see him.

Fleece fugitives

The visit caught the public imagination on both sides of the border and demand for tartan and tweed cloth soared. The mills couldn’t get enough wool. They already imported fleeces from Germany, but now began ordering from Australia too – as well as the Falklands, the Cape, India, South America and New Zealand.

Hidden among the fleeces were some seed hitchhikers that got carried into the rivers and streams with the effluent from the mills. They took root in the landscape, first around the sites of the mills and then beyond.

Ida Hayward with her dog, Logie, from the archives of the Royal Botanic Garden Edinburgh.

Ida Hayward

A few decades later Ida Hayward began recording the plants near her uncles’ wool mill. Over a ten-year period between 1907 and 1917 she walked along the streams and rivers of Galashiels with her dog, Logie. She gathered samples for her herbarium and recorded her findings eventually in a book[1]. Haywood made some astonishing discoveries. In total she found nearly 350 ‘fleece fugitives’.

“Miss Hayward found at Selkirk Nasella flaccidula, a very rare species of beautiful feather grass only occurring over 13,000 feet up the Bolivian Andes on the mountain slopes near La Paz. Its seeds had managed to fix themselves in the fleece of some adventurous sheep and, despite the shearing, the jolting down the mountain railway to Antofagasta, the long sea voyage round the Horn, across the Line, it finally germinated on the Tweed at less than 400 feet above the sea level. In its new home, too, it grew not as the type but as a variety, new to science, which Professor Hackel named glomerata, not as yet discovered in South America.” – George Druce, The Adventive Flora of Tweedside.

Many of the invaders failed to survive long – they died out when sceptic tanks were built to treat the effluent in around 1919 and the continuous flow of fresh introductions to the landscape stopped.

Right: Nassella flaccidula, 1932 (Naturalis Biodiversity Center, CC0 1.0 Public-domain). Left: The River Tweed in Galashiels (Mary and Angus Hogg, CC BY-SA 2.0 via Wikimedia Commons)

Pirri pirri

But some were resilient, including the pirri pirri – a native of south-eastern Australia (and nothing to do with hot food, in case you ask – that’s piri piri!) Australians know it also as the biddy-biddy or the biddy-widgee. Funny-sounding names. Not a funny plant.

First reported in the wild in the UK in 1901, its seeds escaped from wool imported into the port at Berwick upon Tweed. Today the pirri pirri covers huge parts of the Northumberland coast, forming dense low-growing mats that smother the life out of UK native species. It is also recorded along the south coast of England.

Its reddish spring flowers ripen into barbed fruit – or “burs” – which catch on to walkers’ socks and any passing dog or sheep. And so it spreads. And all because of a king who wore a kilt that looked a bit like a mini-skirt.

A caution sign for Pirri-Pirri burrs in Lindisfarne grassland (Des Blenkinsopp, CC BY-SA 2.0 via Wikimedia Commons)

[1] The Adventive Flora of Tweedside was edited by George Druce. “Adventive” means “alien”.

With thanks to the Royal Botanic Garden Edinburgh, which staged an outstanding exhibition on invasive species in the summer of 2023 and which holds Ida Hayward’s herbarium and archives relating to her ‘Adventive Flora of the Tweed’.

Banner image: Pirri Pirri (Stuart Meek, CC BY-SA 2.0 via Wikimedia Commons)

Share this story

About the Storyteller Gardener

Martin Stott is an award-winning journalist who has written for most of the UK national press and reported from 21 countries for the BBC World Service and Radio 4. The storyteller garden history blog combines his passion for storytelling, gardening and history.