Pleurotus populinus

Pleurotus populinus, the aspen oyster mushroom, is a gilled fungus native to North America. It is found on dead wood of aspen and cottonwood trees (genus Populus). Although morphologically similar to Pleurotus ostreatus and Pleurotus pulmonarius, it has been shown to be a distinct species incapable of cross-breeding. P. populinus is reported to be edible. Unlike P. ostreatus, which fruits in the autumn and winter, P. populinus fruits in late spring and summer....read more on Wikipedia.