Abstract: Compost, e.g. hardwood bark, is rendered suppressive to plant pathogens, such as Rhizoctonia solani, Pythium ultimum and Fusarium, and/or diseases caused thereby by adding to the compost, desirably after peak heating has been achieved but before substantial recolonization of the compost by mesophilic microorganisms has occurred, one or more microorganisms antagonistic to the plant pathogen. Container media also is rendered suppressive to plant pathogens and/or diseases caused thereby by amending the media with the just-described prepared suppressive compost or, alternatively, by amending separately with the compost and with Trichoderma fungus and antagonistic bacterium separately or mixed together. Desirably, the inoculated antagonistic microorganisms comprise Trichoderma hamatum species A.T.C.C. No. 20765 or 20764, together with Xanthomonas maltophilia bacterium species A.T.C.C. No. 53199 or a Flavobacterium balustinum isolate 299, A.T.C.C. No. 53198 species, A.T.C.C. No. 53198.