The graphics are really cool. The UI is pretty solid as well.
The gardener's movements were a bit stiff. What you could add to change this would be jump buffering (so you can press SPACE just before landing on the ground) and coyote time (so you can jump a moment after falling of the ledge).
I liked the idea of the thorns, but they had a really huge hitbox, so I kept falling on top of them. I've also found the thorn-destroying flowers nice, but the level introducing them glitched out meaning that I wasn't able to water the topmost left flower.
I didn't really realize that you can fire the water further if you move your cursor further. Maybe getting some indicator, like a ray from the gardener to the cursor would help in showing this. Also maybe hiding the default cursor would be nice.
Getting some music in the levels would help. Also the sprinklers had a really rough looping effect. It stands out quite a bit.
Good job!