"Plants containing methyl salicylate produce this organic ester (a combination of an organic acid with an 
alcohol) most likely as an anti-herbivore defense. If the plant is infected with herbivorous insects, the release of methyl salicylate may function as an aid in the recruitment of beneficial insects to kill the herbivorous insects.[1] Aside from its toxicity, methyl salicylate may also be used by plants as a pheromone to warn other plants of pathogens such as tobacco mosaic virus.[2] Numerous plants produce methyl salicylate in very small amounts."
"Plants producing it in significant amounts (readily detected by scent) include:
- most species of the family Pyrolaceae, particularly those in the genus Pyrola;
- some species of the genus Gaultheria in the family Ericaceae, including Gaultheria procumbens, the wintergreen or eastern teaberry;
- some species of the genus Betula in the family Betulaceae, particularly those in the subgenus Betulenta such as B. lenta, the black birch;
- all species of the genus Spiraea in the family Rosaceae, also called the meadowsweets."