A plant growth support medium is described to enhance soil characteristics and provide where required, improved water, or nutrient contents. La addition the medium can be inoculated with microorganisms to aid soil characteristics and provide interactions within micron-scale environment between plant roots, water, nutrients and where applicable, bacteria and root exudates. This micro-environment provides direct delivery of active ingredients to the plant roots. The medium comprises a polymeric material having a primary pore size of greater than 30 micron. The walls of the pores are elastic, enabling the pore to swell in size to retain water, solutes or other biologically useful components and allow root penetration through them. Sulphonation of the walls renders the walls more hydrophilic so attracting water into the pores and also increasing the wall elasticity. Capillaries can be provided to interconnect pores and allow root penetration into the medium. The pore walls can be granular in character to allow water, nutrient and where applicable, bacterial metabolites and messenger molecules passage between adjacent pores and plant roots.