Greenhouse studies were conducted to test allelopathic effects ofArtemisia campestrisssp.caudataon seed germination and seedling growth of several sand-dune species and colonization by mycorrhizal fungi. The aqueous extracts ofA.campestrisshowed no inhibitory effect on seed germination, seedling elongation, or dry-weight growth of plants at lower concentrations (10 and 50%), but 100% concentration of the extracts caused varying degrees of inhibition depending on the test species. The mixing of dry leaves of seedlings ofA.campestristo the sand showed severe inhibition ofElymus canadensisseedlings. The percent germination of test species in soil from the rhizosphere ofA.campestriswas significantly lower than that of the control. The leaf area and dry weight were also lower but the differences were not significant. The aqueous extract inhibited mycorrhizal fungal colonization in roots of three sand-dune grasses.Key words: allelopathy,Artemisia campestrisssp.caudata, seed germination, seedling growth, mycorrhizal fungi.