Crops are used in recipes and also to create other ingredients (such as chicken and milk) for recipes.
To grow and harvest crops, click on your empty garden plot and a menu of all of the crops that are available to you, together with the times they take to grow, will appear.
After selecting the crop that you want from the list, click on your garden plot to grow it. After the allotted time, your crop will be ready to harvest. Tap on the crop to harvest it. You will harvest 2 crops from every plot.
Once you have unlocked trading (level 7) you can sell crops on the market for coins.
In order to grow new crops, you must have at least one of the crop in your inventory. If you accidentally use your last crop you will be given a free one to plant.
New varieties of crops will become available for you to plant as you advance in the game.