Very cool concept for a game, I like it ^^
The graphic looks pretty polished and there is some sound design so nice work.
The only thing is that it is pretty tough to reach day 60 and beat the game. My high score was around 50 or something but this also can present a challenge. My game was also very hard to balance in such a short time and it turned out to be a little to hard so I know how hard it is.
I really like the idea of other plants growing over time that you have to destroy to get more trees, because this adds a risk-reward system where you have to decide if you going to get energy or destroy some plants.
So all in all a very cool game.