Bracken: The Fern That Took Over the Hills

Each major claim carries one of three labels. established means supported by primary records, official bodies or several independent reliable sources. shared means the core fact is sound but sources disagree on details, dates or interpretation. traditional means widely repeated but not traceable to a primary or independent source.

Estimates of the area covered by bracken in Scotland vary, so this card does not give a figure. The causes of bracken's spread involve several factors, and historians weigh them differently.

The plant

established Bracken is a large fern with tall, much-divided fronds that unfurl in spring from tightly curled "fiddleheads". It spreads by a network of underground rhizomes, which store energy and allow it to regrow after cutting or burning. It forms dense stands that shade out other plants. In autumn, its fronds turn golden and russet.

A useful plant

established For centuries, bracken was a valuable resource. It was cut for animal bedding and thatch, burned as fuel, and its ash, rich in potash, was used to make soap and glass. Harvesting and cattle trampling helped keep it in check.

established Richard Mabey, in Flora Britannica (1996), quotes the naturalist John Lightfoot's Flora Scotica (1777) on how this worked in eighteenth-century Scotland. People mowed the bracken green, burned it to ash, made the ash into balls with a little water and dried them in the sun, then used the balls to wash linen instead of soap. In many of the western isles, Lightfoot wrote, people made "a considerable profit" selling the ash to soap and glass makers. Mabey also records experiments in the Highlands in the late nineteenth century in making bracken silage. Stock ate it greedily, but the practice never caught on.

established Elsewhere in Britain, Mabey lists bracken as manure and a cover for potato beds, fuel and tinder, a dressing for fine leather, and packing for slate, earthenware, fruit and fish. Most of these uses ended with modern packaging, and he notes that where bracken is no longer cut, it spreads.

Names and badges

established Peter Marren's appendix on Scottish plant names in Flora Britannica gives the Scots name as breckan, or simply "fern" or "great fern". The Gaelic raineach mhòr also means "great fern", and bun rainnich are bracken roots.

shared Mabey notes that bracken has "an honourable place" on the badges of the Robertson and Chisholm clans. Published lists of clan plant badges vary, and some give fern in general rather than bracken specifically.

Spreading over the hills

shared In the late eighteenth and nineteenth centuries, many Highland estates replaced cattle with sheep. Cattle trample bracken, while sheep avoid it. The decline of bracken harvesting removed another check. Over the twentieth century, bracken spread widely across the uplands, reducing grazing. As a measure of how uncertain the figures are, Mabey cited estimates that by 1990 bracken covered somewhere between 1.2 and 2.7 per cent of Britain's land surface. That wide range is for Britain as a whole and is now dated.

Poisonous and dangerous

established Bracken contains thiaminase, an enzyme that destroys vitamin B1, causing illness in horses and pigs, and ptaquiloside, a compound linked to cancers in cattle. Its spores may also pose risks to human health, though the evidence is debated. Dense bracken provides a humid habitat for ticks, which can carry Lyme disease.

Control

established Bracken is controlled by repeated cutting, rolling or crushing, herbicides and grazing by cattle. Control is expensive and must be sustained for years. Bracken also provides habitat for some species, including certain butterflies and birds, so conservationists seek a balance.

• Bracken can grow up to two metres tall.
• It was once harvested for bedding and thatch.
• Bracken ash was used to make soap and glass.
• Cattle trample bracken; sheep avoid it.
• Bracken provides habitat for ticks.
• In eighteenth-century Scotland, balls of bracken ash were used to wash linen instead of soap.
• The Scots name is breckan, and the Gaelic raineach mhòr means "great fern".
• Bracken appears on the plant badges of the Robertson and Chisholm clans, according to Richard Mabey.

• Do not give a precise area covered by bracken.
• Do not present bracken spores as a proven human cancer risk.
• Do not use Mabey's 1990 Britain-wide coverage range as a current figure or apply it to Scotland alone.