The autoallelopathic effects of date palm leaflets and seed aqueous extracts, with -0.05, -0.1 and -0.2 mPa osmotic potentials, on seed germination and carly scedling growth were investigated. Final seed germination percentage, seed germination rate, the time of radicle appearance, and plumule length were not affected. In contrast, the cotyledonary sheath and radicle lengths were significantly retarded, whereas the time of plumule appearance was significantly increased by most of the extracts in comparison with the distilled water control. Mannitol solutions, with the same osmotic potential and pH as the extracts, resulted in significantly longer cotyledonary sheaths and radicles and an earlier plumule appearance than their corresponding extracts. Thus, it could be deduced that date palm leaflets and seeds contain water-soluble allelochemicals that could substantially retard early seedling growth of the same species.