Provided is an expandable, modular tower planter having an internal vertical composting capability, and a method of assembling and using the same. Provided in various example embodiments is a modular composting garden container system comprising a base and a plurality of stackable rings forming a tower upon the base, including an optional base ring specially sized, shaped, and positioned to connect the tower to the base. A plurality of perforated, stackable tube sections are provided that are removably assembled into a compost tube assembly of selectable height and mounted within the interior of the tower and above the base. A plurality of holding struts are sized, shaped, and positioned to removably connect the compost tube assembly with the tower and to securely locate the compost tube assembly relative to the tower. Means are provided for recovering nutrient-rich drainage and selective recovery of compost material for reintroduction into the system.