A cool game with some fun surreal visuals.
For game balance, one suggestion - there should be a tower that has higher range. Once the tree started growing, it was basically useless to put new plants at the tips of the roots, because there were huge gaps between the "spokes" that the humans could just walk through. So I ended up crowding all my units near the trunk where they were guaranteed to hit the humans.
If we're going to have gaps like that, there should be a longer range (but weaker? more costly?) unit, which could add more strategy on what to build and where.