Simple and relaxing game. The weeds to indeed get out of control as the level progresses.
The powerups spice things up. However, their effects could be more clear. I don't know what the scythe powerups do. Increased damage? Weeds seem get cut in one hit regardless though. Perhaps increase weed durability and/or cut range.
Weeds grow if you leave them which is a nice touch. Perhaps they could also block the player's way when up to a certain height. Or they might turn into monster plants. You can do a lot with this.
You might also want to have a combo system to reward good players.
Overall, this is a very solid entry with cure pixel art. Good job!