Fun game! I really like how if you cut a flower you loose all of the bonus points you've been given. That's not something I see to often and it creates a nice incentive not to just spam everyone on the screen.
If you wanted to improve, an in-game tutorial could be more useful then the text guide. Additionally, instead of power-ups you could implement an in-game shop where you can buy upgrades. Doing this plus making the levels shorter could condense the primary game-play loop into a cycle of always trying to get that next upgrade to make your self just a little more efficient. Furthermore, more types of flower could be nice, maybe a flower that grows for a bit then dies and you have to cut it out.
Overall, fun game!