There are many different types of willow trees and not all of them have high levels of salicylic acid. Salicylic acid is the active pain-relieving and anti-inflammatory component that is used to make aspirin. The types of willow trees with the highest levels of salicylic acid include:   Salix alba (White or European Willow)  Salix purpurea (Purple Willow)  Salix nigra  (Black or Pussy Willow)  Salix fragilis (Crack Willow) Your best bet is to find a white willow tree. White willow trees grow throughout much of the US, Europe and Asia and they are common in forested areas. Features of a white willow tree include:  A rough grayish bark Irregular “furrows” Smaller branches and twigs that are slender, golden brown and flexible Leaves that are long and slender (2–4 inches long) with a fine serration at the edges Tops of the leaves are shiny and green, while the undersides of the leaves are white and silky Leaves alternate instead of being opposite one another All willow trees all contain some amount of salicylic acid in the bark, so it is okay to use a different type of willow tree. For example, if you are by a river, then you can use a river weeping willow. When in doubt check the leaves to see if they share the features of white willow leaves. Willow tree leaves are distinctive, so checking the leaves may be the best way to identify the tree as a willow. Once you find a willow tree, try to find some loose bark and pull it off. As you pull off the bark, make sure that you are getting the papery material that underlies the bark. It is a good idea to strip the bark from younger branches rather than the trunk. The bark from the trunk is harder to remove and it is also tougher to break up for boiling.
اعرف أنواع أشجار الصفصاف المحتوية على أكبر نسبة حمض السلسليك. ابحث عن شجرة الصفصاف الأبيض أولًا. تذكر أن أي شجرة صفصاف ستؤدي الغرض. اجمع بعض لحاء الصفصاف.