As early as the 5th century BC, Hippocrates the father of medicine was recommending taking a bitter extract of willow bark to ease aches and pains. How this ancient herbal remedy lead to the discovery of aspirin is a tale complex enough to give you a headache, with various scientists staking a claim and two very different plants vying for the starring role.
It is a commonly held misconception that willow bark contains aspirin, this is simply not true. The pharmacologically active chemical in willow is salicylic acid, which derives its name from Salix the Latin name for willows. A less widely believed tradition claims that the bitter taste of willow bark results from Christ being whipped with a willow wand as a child. In fact salicylic acid is not unique to the willow but is widespread in the plant world, where it acts as a plant hormone, involved in stress tolerance and disease resistance. In a few plants such as willows and meadowsweet, salicylic acid is present in high enough concentrations to be medically active and to the extent that it is potentially toxic to species feeding on them. In Europe robins feeding on the seeds of meadowsweet come close to taking a lethal dose, while in North America, beavers which eat excessive quantities of willow bark escape poisoning by perspiring salicylic acid.
In its pure form salicylic acid was first extracted from willow in 1828 by the French pharmacist, Henri Leroux and from meadowsweet in 1839. Although salicylic acid does relieve pain it is not an ideal medicine because it causes digestive problems, including gastric irritation and diarrhoea. Therefore, throughout the 19th century chemistry struggled to develop a less irritating formulation for salicylic acid. By 1853 Charles Frederic Gerhardt had synthesised acetylsalicylic acid (the compound later named aspirin) and even marketed the product during the 1880s. However, the discovery of aspirin has been widely credited to a German, Felix Hoffmann working for the drug company Bayer in 1897. The story goes that Hoffmann was looking for something to relieve his father’s rheumatic pains. Acetylsalicylic acid was marketed as aspirin from 1899, a name derived from the then Latin name for meadowsweet (Spiraea) and not willow! In 1949, shortly before his death, Arthur Eichengrun another German chemist working for Bayer at the time, cast doubt on this story when he made a credible claim to have been responsible for directing the research at the time. Whatever the truth of the story in the laboratory, the fact remains that the naturally occurring chemical is as effective today as it was in the time of Hippocrates, so if you are ever stuck in the Canadian wilderness with a stinking headache, you main gain relief by licking a sweaty beaver!
Willow trees have a long history of being used by man, but hardly one that qualifies them the status of crop. Taxonomically willows are a nightmare, as their lack of morals means that virtually every species hybridises with every other, from low growing creeping willows found in sand-dunes or mountain tops to magnificent stately trees. The resulting range of growth forms have provided humans with a wealth of material for weaving into wickerwork to a strong lightweight timber favoured for making artificial limbs. Probably the most famous use of willow wood is in the production of cricket bats, without which English civilization would cease to function. Only rarely are plants defined by a single human use, but the cricket bat willow has such an honour.
In complete contrast the future of willow as a crop is far removed from the genteel English past-time of cricket. In the 21st century willow is being grown on a vast scale in enormous monoculture plantations across prime agricultural land. This industrialisation of sustainable short-rotational coppicing is far removed from the flower-rich coppice woodlands of old. Willow’s rapid growth and re-growth rates may be part of the solution to the world’s growing demand for renewable energy, but the agricultural landscape associated with its cultivation would be very unfamiliar to Ratty and Mole and their willow wicker basket.