Abstract: A modular, threaded container for growing plants and subsequently increasing size of the container. Modules are arranged to be stacked on one another to increase overall height of the modular assembly. Individual modules include a top module having bottom threading only, intermediate modules open at the top and bottom and having top and bottom threading, and a bottom module having a floor and threading at the top only. The container may optionally include frustoconical modules, a first frustoconical bottom module configured to replace an open intermediate module with a module closed at the bottom, and a second frustoconical module closed at the bottom of dimensions and configuration different from those of the first bottom module. The plant is grown in a container having relatively few modules. After growth has occurred, the bottom module is removed and an intermediate module open at both ends is filled with growing medium and is inserted in series prior to replacing the bottom module.