After researching and building the Forester on the verge of a dense forest, the farmer grows saplings and stores them. However, no villager makes an effort to plant them.
I have even given my apprentice farmer a sapling while he was idle only for him to immediately take it to storage.
I also took the same farmer to a location where trees had been cut AFTER the Forester had been built. Same result; he takes the sapling to storage with no effort to plant.
I've tried different priorities, different settlers, different locations... Nothing.
Hundreds of saplings in storage, no trees to be found.