Solaray, White Willow, 400 mg, 100 VegCapsNon GMO 100% Vegan Dietary Supplement Salix Alba 400 mg Per Capsule Whole Bark Lab Verified White willow is a deciduous tree native to central and southern Europe. The bark of the white willow tree has a long history of use as a medicine dating back to ancient Egypt and Greece. White willow bark was one of the first herbs to be scientifically studied. The bark contains a glycoside known a salicin, believed to be the source of its health benefits.