I have read that wearing the grren willow goes back to the Monmouth rebellion of 1685 when the failed attempt by a "pitchfork army" against James 11 professionals lead to widespread executions anh transportations in the west country. Wearing a green garland was a secret way of showing support for rebels who had been transported far far away.Most never returned to their sweethearts so it was also a sign of sadness and loss.