PURPOSE: To effectively utilize waste coffee grounds as a culture medium composition for cultivating a plant by mixing particles of coffee grounds and those of a a clay mineral having a specified base exchange capacity.
CONSTITUTION: A plant cultivating composition consisting of particles of coffee grounds comprising a coffee extraction residue and particles of a 2:1 type clay mineral having a base exchange capacity (CEC) of at least 60mg equivalent (me). It is desirable that the composition contain the clay mineral in an amount of 1-10 pts.wt. based on 100 pts.wt. air-dried coffee grounds. Representative examples of the clay mineral to be used include montmorillonite, vermiculite, and sericite. It is desirable that the particles of coffee grounds serve to bind those of the clay mineral by the action of moisture contained in the coffee grounds so that the composition presents an appearance of dried particles.