Many edible and medicinal mushrooms can be grown on a variety of freshly cut trees. Select the right type of tree that is suitable for the type of mushroom you would like to grow.
Most cultivated species, like oyster and shiitake, grow on hardwood logs from deciduous trees such as maple, oak, and alder. A few cultivated species, such as Hericium abietis, grow on coniferous trees.
The logs you inoculate must be from a tree that has freshly fallen or been recently cut down. (Dead wood that is aged more than a couple months will already be colonized by competitor mushroom species.)
The best time to harvest a tree is in the late winter time, because the sugar content is highest and the bark tends to stay on the log longer.