In the 16th and 17th centuries this unfortunate-looking plant was widely believed to fruit newly-born lambs. According to an ancient legend, the “vegetable lamb” plant sprouted living lambs as if they were flowers. (See the 17th-century illustration, below.) It was assumed that the lambs fed on surrounding grass, but that once all the foliage had been munched away they would shrivel up and die—and so the plant would come to resemble its 19th-century incarnation (above) preserved in London’s Museum of Garden History.

Now scientists have discovered a less far-fetched, though potentially revolutionary, purpose for this ugly fern (proper name: Cibotium barometz). A study in the Journal of Natural Products has found that it could hold the key to a breakthrough treatment for osteoporosis.

About 3m people in Britain suffer from the bone-thinning disease, which leads to an estimated 230,000 fractures every year: half of women over 50 injure themselves as a result of the condition. Its causes are still not fully understood, but doctors do know that healthy bones contain a balance between two types of bone cells: osteoblasts, which build up bone, and osteoclasts, which break down bone. During a wider study of folk medicine in Vietnam, researchers isolated compounds from the “vegetable lamb,” and discovered that they blocked formation of bone-destroying osteoclasts in up to 97 per cent of the cells tested in the lab—without harming other cells.

While a marketable treatment is still many years off, this does mean an extraordinary turnaround for a plant that was once thought to have little purpose beyond sating the appetites of passing wolves.