TIP: Oyster Mushrooms (Pleurotus ostreatus) are wildly delicious, wood-loving mushrooms that can be found throughout Illinois from early spring until early winter. Mushroom hunters often find them at their peak during late autumn, sprouting in clusters on trees and fallen logs. Oyster Mushrooms can appear right up until bitter cold weather sets in. Different varieties of Oyster Mushrooms are easily cultivated today--but nothing beats the wild and free rewards of foraging in nature.