To harvest your crops, all you have to do is click on them when they are ready.

As your crops are harvested, they will pop up off the farm plot, and bounce around near where they were planted. To gather the crops into your Inventory you can just swipe your mouse pointer over them, or wait a few moments and they will automatically go to your Inventory.

Tip: You can quickly plant, water and harvest crops by clicking and dragging your cursor over plots.