Abstract: A soil-less biodegradable and porous rigid foam substrate for cultivating plants that has been formed of a heterogeneous matrix of organic fibers pasteurized with organic matter and natural minerals, and then contacted with a fungus, resulting in a biocomposite foam with excellent capillary dynamics, the whole of which does not compact and whose organic bio-composition favors the proper micro-biological activity upon a plants' rhizosphere. The preferred embodiment is to grow said substrate inside a waxed hexagonal prism shaped box, and around an externally accessible means of internal aeration, for approximately 3-5 days, and then to deactivate the live fungus in said biocomposite foam by exposure to microwave radiation.