also i think that there should be a sun that moves across the sky and the tree should change the direction that it grows in based on where the sun is by growing towards it like an actual tree or any plant really would do in real life. and i think that there should be a night time as well and the tree should slow its growth or stop it completely during this time.
personally i really like it but i agree with the top comments that there is definitely some thing missing to this game. there is a lot of room for improvement but i think you have the basis of something truly great beginning to shoot upward instead of just a tree!