Citrus trees that are planted outdoors require watering about once a week, according to Gardening Know How. Soak the ground deeply and thoroughly if the area surrounding the tree has good drainage. For citrus trees planted in areas of poor drainage, reduce the watering schedule to avoid over-watering the tree.
Watch carefully to ensure that container citrus trees do not become overly dry. Water right away when the soil becomes dry or barely damp. It is very important that container citrus trees never become dry for more than a day or so. Trees that receive insufficient water may lose their leaves.