This unusual citrus tree is a cross between kumquats and mandarin oranges. This gives the fruit a slightly sour taste, but the skins are sweet. A ready to harvest calamondin has a firm feel and should snap easily off the tree’s branch. When grown indoors, pot the tree in a large container filled with potting soil, organic compost, and vermiculite. Water the tree as needed to keep the soil moist and provide direct sunlight for at least several hours daily.