Coulman, B., Loeppky, H. and Entz, M. 2015. The effect of late fall seeding time on the seed production of Italian ryegrass. Can. J. Plant Sci. 95: 641-645. Italian ryegrass (Lolium multiflorum Lam.) is a cool-season grass, which behaves as an annual in the Great Plains region of western Canada and is used as a grazing crop. Italian ryegrass requires vernalization for reproductive development to occur. Late fall (dormant) seedings, which have been used for annual crop species, have often resulted in earlier developing seedlings in the spring and higher yield than spring seedings. For Italian ryegrass, dormant seedings may result in vernalization of early-spring-germinating seedlings, allowing seed production without having to overwinter established plants. The objective of this study was to compare the seed yield and stand establishment of late fall (dormant) and spring seedings of Italian ryegrass at three locations in the Great Plains region of western Canada. Stand establishment was assessed by measuring tiller density in the month of June, and these densities were greater for spring than late fall seedings. Most spring seedings had no reproductive development and, thus, no seed yield; however, most late fall seedings produced seed the following year, indicating that vernalization of early-developing seedlings did occur. There were significant differences in seed yield among the four cultivars tested and among sites. Based on the high variation in seed yield among cultivars and sites and the relatively low yield levels obtained, late fall seedings of Italian ryegrass cannot be recommended in the Great Plains region of western Canada.