Salix is the genus name of willow, trees known and cultivated for millennia for their medicinal properties.
The first written records of the use of willow bark to alleviate pain and fever date back nearly 4000 years to the ancient civilisations of the Assyrians and the Sumerians. The key active component of willow, salicylic acid, was first identified in the 4th Century BC by Hippocrates, who isolated a white powder from solutions made with willow bark.
 Ancient Assyrians;  Hippocrates;
Salicylic acid is the basis of aspirin, a medicine taken daily by millions to reduce fever and inflammation, to manage pain, and to prevent cardiovascular and cerebrovascular disease. The latest studies show that it may have a protective role against some types of cancer.
Since the middle of the 19th Century the salicylic acid used to make aspirin has been synthesised rather than extracted from willow bark. Marketed under all kinds of copyrighted names, aspirin is now the most commonly used drug in the world;
 salicylic acid was originally extracted from willow bark;  one of the park’s ancient willow trees.
There are many willow trees of several different species in the park: ancient, moss covered, white willow pollards along the path by the Lambrok Tributary and islands of young goat willows, no more than 20 years old, in Sleeper Field.