So maybe it is only a minimal benefit for ID help. But my experience in late May and June with Pleurotus sp. on Populus grandidentata is that the odor is usually much stronger of anise (anisette) than oyster mushrooms on other hosts.

www.bio.utk.edu/mycology/Pleurotus/Species/P_populinus.htm
INTERSTERILITY GROUP III. Pleurotus populinus O. Hilber and O.K. Miller in Vilgalys et al. 1993.

Nomenclatural history: The species epithet is quite recent, and therefore has not been transferred. Although it appears strange to have the authors of the epithet different from authorship of the paper, this is straightforward and in accordance with the ICBN.

Typification: Holotype: UNITED STATES, Idaho, McCall, 27.VI.80, O.K. Miller no. 18812 (VPI).

Taxonomic history: Until recently, two names were used for North American pleurotoid (not strongly stipitate) species of Pleurotus: P. ostreatus and P. sapidus. The latter is better represented by P. pulmonarius. Pleurotus populinus was identified using compatibility tests, when collections chiefly from Populus wood were found to be incompatible with collections under either common-usage name. Morphotaxonomic characters for identification of P. populinus are subtle and difficult, centering on its common host, Populus spp.