Pleurotus euosmus, also known as tarragon oyster mushroom, is a species of edible fungus in the genus Pleurotus, It is quite similar to the better-known Pleurotus ostreatus, but it is distinguished by its strong smell reminiscent of tarragon and substantially larger spores.
This mushroom is saprotrophic and can also be a weak parasite. It occurs in stumps and fallen trunks, preferring elms. It is fairly rare, limited to the British Isles, reported only in England and Scotland.
Pleurotus euosmus is quite similar to the well-known food mushroom Pleurotus ostreatus, to the point of Watling & Gregory having considered P. euosmus a variety of P. ostreatus. However, later phylogenetic research has shown it is more closely related to Pleurotus citrinopileatus and Pleurotus cornucopiae, belonging to their intersterility group in P. djamor-cornucopiae clade.
This mushroom is edible and it can be cultivated in a manner similar to P. ostreatus. It is cultivated by individual hobbyists, but not cultivated on a wide/commercial scale.