We are in the situation, where game blocking you from planting trees during ~20-23 days, when the trees don't have seeds during winter, spring, and few first days of summer, and this is the one side. The other side is that common sense will never allow you to make it so, that trees will have seeds during these seasons.
Moreover, game came to the state, when you have multiple ways to plant tree, and i think we can consider a new way for planting trees - tree cuttings. As i know, literally any tree can be cloned with pruned branch being placed in certain conditions.
By having certain skill, Foresty for example, you will be able to strike 1-2 cuttings from a tree any season. This cuttings can be planted in treeplanters pots, just like other tree seeds. Tree cuttings cant be planted directly in the ground.