A foamed glass plant growth support structure, including a foamed glass substrate and a plurality of interconnected pores distributed throughout the substrate. The substrate is characterized by a porosity of at least about 65 percent. The pore size is substantially between about 0.2 and about 2 millimeters and the substrate is sufficiently chemically stable such that water filling the plurality of interconnected pores experiences a pH shift of less than 0.5.
