Very relaxing game although there isn't much to it. Some suggestions:
Display the movement controls at the start (or atleast in the game's description). You can run in this game with shift but I only discovered that because I instinctively press it to run in other games. Other people might not discover and would think the game is slow.
The shop UI's cost numbers should be in a colour other than black. Since the background of the shop is also dark, it's hard to see what every plant costs.
The later plants take too much time to grow so that the most optimal way to farm is probably to only potatos and onions as they are fast to grow and give a bigger percent return on their cost.
The tomato plant doesn't seem to have a visible model while growing.
Add some kind of relaxing music to help the mood of the game. The occasional chicken sound effect and others are nice though.