Wintergreen essential oil is water steam-distilled from leaves charged into the still and allowed to macerate for several hours to hydrolyze the gaultherin glucoside (methyl salicylate + glucose). Distillation lasts from 5 to 6 hours and yields approximately 0.7% essential oil. The oil is often adulterated by intentionally co-distilling sweet birth (Betula lenta) bark. FCC (1996) has described wintergreen oil as obtained from the leaves of G. procumbens and bark of B. lenta. The oil has a strong, sweet, aromatic odor reminiscent of methyl salicylate, its main constituent.