We evaluated the allelopathic potential of two selected Eucalyptus species (Eucalyptus salubris F. Muell. and E. brockwayii C.A. Gardner) on noxious perennial weed prairie ground cherry (Physalis hederifolia A. Gray). Steam distillation of eucalyptus leaves produced two bioactive fractions: essential oil fraction and the aqueous volatile fractions (AVFs). Both the essential oils and the AVFs inhibited the germination and growth of prairie ground cherry, however, the essential oils of E. salubris and E. brockwayii was more inhibitory than commercial eucalyptus essential oil. In addition, the inhibitory effects of E. salubris on the germination and growth of weed were higher than E. brockwayii. At 0.15 ml/L oil concentration, E. salubris inhibited the germination and seedling growth of prairie ground cherry by 94-95% and completely suppressed these at concentrations > 0.45 ml/L. The AVFs of both eucalyptus species also completely inhibited the germination and seedling growth at 75% AVF concentration. In glass house, the foliar application of essential oils severely damaged the seedlings of prairie ground cherry. At 21 days after foliar application, the E. salubris essential oil at 20% concentrations complete killed 5-leaf old seedlings. Thus eucalyptus essential oils could be further exploited to control weeds in integrated weed management.