Field experiments were conducted during two growing seasons to investigate the effect of different Common thorn-apple (Datura stramoniumL.) densities on seed production of this specie. Maize (Zea maysL.) was planted in 2.1 m rows with a plant population of 16000 plants. ha−1.D. stramoniumwas planted at five densities in association with maize. The time of weed seed production, total seed production of eachD. stramoniumplant and of each plant population were determined. Seed production ofD. stramoniumdecreased with increasing density stress, with a substantially greater effect during an unfavourable season. The study provided information on timing of weed control and the implications of weed seed contamination in the absence of weed control. This may contribute to more effective, economic and environmentally friendly weed control.