Nevermind. I figured out you have to dig a hole first with the hoe to plant a seed. It is working. You might want to explain this in the description. Nice game by the way.
It's very bare-bones. Got the most powerful upgrade in under five minutes. After that, there's nothing left to do. Try turning it into a proper game with more upgrades (fertilizer, grow speed, different levels, for example) and a prestige mechanism.