Bootsma, A. 2011.Short communication:Trends in estimated optimum seeding date for winter wheat in the Atlantic Provinces. Can. J. Plant Sci. 91: 1101-1103. Seeding date is an important management factor affecting the performance of winter wheat (Triticum aestivum L.) in the Atlantic region of Canada. In this study, decadal trends in estimated optimum seeding dates were estimated from air temperature in September and October at nine locations in the Atlantic region of Canada from as early as 1899. The optimum seeding period averaged over all locations was delayed by 8 d for the past 10 yr compared with earlier decadal periods. If the warming trend continues, producers will be able to seed winter wheat successfully at dates later than previously recommended.