Effect of Calcarisporium arbuscula on adventitious root development in leaf-bud cuttings of two elepidote rhododendron cultivars was studied. Guaiacol peroxidase activity was determined and anatomical study was performed in untreated cuttings (control), and cuttings treated with 1% indole-3-butyric acid (IBA) or C. arbuscula . In rhododendron cv. ‘Babītes Lavanda’ both IBA and C. arbuscula treatment slightly delayed adventitious root formation; the overall rooting percentage remained high (94 and 92%, respectively) but lower than in the control (96%). IBA and C. arbuscula treatments had a strongly positive effect on long term survival of rooted cuttings (73 and 70%) compared to the control (58%). There was no difference in peroxidase activity between the treatments. In rhododendron cv. ‘Nova Zembla’, IBA and C. arbuscula treatments promoted formation of adventitious root initials and primordia as well as strongly increased rooting percentage (63 and 70%) compared to the control (38%). In addition, peroxidase activity was significantly higher in C. arbuscula treated cuttings during the whole experiment.