Fourin vitro experiments were set up to verify the colonization potential of ectomycorrhizal (EcM)Cenococcum geophilum Fr. (strain CGE-4), saprotrophicGeomyces pannorum (Link)Sigler & Carmichael (GPA-1) and a frequent root-associated, potentially ericoid mycorrhiza (ErM)-formingMeliniomyces variabilis Hambleton & Sigler (MVA-1) in roots ofRhododendron andVaccinium. A typical ErM fungus,Rhizoscyphus ericae (Read)Zhuang & Korf (RER-1), was included for comparison. All fungal strains intracellularly colonized rootedVaccinium microcuttings: GPA-1 occasionally produced hyphal loops similar to ErM, MVA-1 and RER-1 exhibited a typical ErM colonization pattern. CGE-4 hyphae grew vigorously on and around newly formed roots and rarely penetrated turgescent rhizodermal cells forming intracellular loose loops. Rooting ofRhododendron sp. microcuttings was not promoted by any fungal strain except CGE-4, which also promoted the most vigorous growth ofRhododendron ponticum L. seedlings. The widespread EcM fungusC. geophilum has a potential to colonize non-EcM roots and support their development which may influence overall growth of ericaceous plants. As shown forG. pannorum, structures resembling ErM may be formed by fungi that are to date not regarded as ericoid mycorrhizal.