Fun game, great art, and a good concept, but I feel the progression is too slow early game because of how long it takes trees to spawn, even with upgrades. You could definitely introduce some new skills in the tree to influence spawn rate other than straight spawn rate (eg. double spawn chance, chance for immidiate full forest spawn).
More chest tree upgrades would be cool as well (more loot, etc.) I also think this game could benefit from a second phase of gameplay like processing the logs into boards or something to that effect. I think implementing some of these ideas could help the progression and help the game feel less monotonous and more developed.