A porous glass plant growth support structure, including a porous glass substrate and a plurality of interconnected pores distributed throughout the substrate. The substrate is typically formed from foamed glass and/or fused glass spheres and is characterized by a porosity of at least about 80 percent. The pore size is substantially between about 0.2 and about 5 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.
