Lantana camara, a terrestrial plant, was screened for allelopathic impact on water hyacinth (Eichhornia crassipes). Water hyacinth was allowed to grow in experimental pots containing 3% aqueous leachate (w/v) of Lantana twigs. The leachate was allelopathic to the growth of water hyacinth, and killed water hyacinth after 21 days under the experimental conditions. Leachate concentrations from 1–3% of Lantana were highly toxic to water hyacinth plants. Leachate from young Lantana twigs with prickly orange, pink, and yellow flowers (multicolored) was more toxic than leachate from mature twigs. This study indicates the potential for utilization of terrestrial allelopathic species such as Lantana camara to suppress the growth of water hyacinth.