Aspirin From a Tree The inner bark of poplars and other trees related to willows can be used just like aspirin for fevers, as a pain reliever, and to reduce the swelling of injuries. The inner bark contains the compound related to aspirin called salicin. In a wilderness survival setting, knowing how to harvest and use the salicin in tree bark is the most valuable natural medicine knowledge you can have. Salicin concentrates in the inner bark of trees and shrubs related to willows which include: Populus tremuloides, : Quaking, Trembling or American Aspen (northern & western North America) Populus grandidentata: Bigtooth Aspen (eastern North America, south of P. tremuloides)white willow/European willow (Salix alba)black willow/***** willow ( Salix nigra )crack willow ( Salix fragilis )purple willow ( Salix purpurea) weeping willow ( Salix babylonica ) During the spring and early summer it is an easy matter to peel the bark from trees and either chew it directly or steep it in hot water to make a tea. Simply cut into the bark and strip it off. The smell and taste of poplar bark is very aspirin-like and bitter. You can chew a mouthful of bark and swallow the liquid if you are in a hurry and don't mind the taste. An alternative is to simmer about 2 teaspoons of the inner bark in cup of water for ten minutes and let cool before straining and drinking. Three or four cups of this bark aspirin tea can be consumed daily. As with anything you harvest from nature, take only what you need and leave the rest. Do not deface a large tree by removing bark directly from its main trunk. Instead remove small branches so as to limit damage.