First, click on the Market button in the lower-right corner of the game.

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Select the crop that you want to plant.

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After selecting a crop, you are back at your Farm and ready to plant. Crops need an empty farm plot in order to be planted. Just click on the empty Plots while the crop is on your mouse pointer and it will be planted.

Tip: Plant crops that fit your schedule. Select a crop with the suitable harvest time. Planning ahead can save you the hassle of withered crops.