Fallen leaves can be found under Autumnwood trees in forests.
Once a block of fallen leaves are picked up, there is no way to place a "fallen leaf" back down. Picking up fallen leaves would instead yield Mocha Autumnwood leaves.
Fallen leaves do not respawn naturally. They are part of the current world templates TW 1-8. However, it is possible to "create" fallen leaves by using a plow on any sort of Autumnwood leaf block.
Autumn Leafis may spawn on fallen leaves.As fallen leaves aren't considered "full" leaves, corruption won't effect it.