. 2005. Companion crop establishment of short-lived perennial forage crops in Saskatchewan. Can. J. Plant Sci. 85: 135-146. Short-lived perennial forages may provide producers with a cash hay crop as a viable option to diversify annual grain rotations. Little or no information on alternative annual crops for companion crop establishment of forages is available for Saskatchewan conditions. We evaluated field pea (Pisum sativum), canola (Brassica napus), and Westerwolds ryegrass (Lolium westerwoldicum) as companion crops over 3 yr (1998)(1999)(2000) at three Saskatchewan sites: Swift Current (Brown soil zone), Saskatoon (Dark Brown) and Nipawin (Dark Gray). We also compared three short-lived, vigourous grass species in mixture with two alfalfa (Medicago sativa) cultivars or monoculture. Combinations of precipitation and temperature variables combined with companion crop plant density and biomass explained 90% of the variation in forage yield loss relative to no companion crop forage yield. We conclude that companion crops can be used with low yield reductions at Nipawin, but that all three companion crops significantly reduced forage yield at Swift Current. Forage seedling density was reduced under companion crops but the decline in forage seedling density did not explain the reduction in forage yield. We speculate that yield components rather than plant density must have been affected by companion crop competition. Intermediate wheatgrass (Elytrigia intermedia) produced higher forage yield than Dahurian wildrye (Elymus dahuricus) or slender wheatgrass (Elymus trachycaulus). Grass-alfalfa mixtures produced higher forage yield than grass monoculture. Economic returns were superior if no companion crop was used to establish the forages at Swift Current and Saskatoon; but, at Nipawin economic returns were generally higher with companion crop establishment. The feasibility of companion crops for establishment of short-lived perennial forages in Saskatchewan thus depends on soil zone, with their use best suited to the more humid regions.Key words: Forage yield, plant density, weather, economics Jefferson, P. G., Lyons, G., Pastl, R. et Zentner, R. P. 2005. Les plantes associées dans les cultures de vivaces fourragères de courte pérennité en Saskatchewan. Can. J. Plant Sci. 85: 135-146. Pour les agriculteurs, les vivaces fourragères de courte péren-nité pourraient devenir une option valable comme culture fourragère monnayable pour diversifier les assolements annuels de céréales. Pourtant, on ne sait rien ou pas grand-chose des cultures annuelles qui faciliteraient l'établissement de plantes associées dans les conditions particulières de la Saskatchewan. Les auteurs ont évalué l'utilité du pois de grande culture (Pisum sativum), du canola (Brassica napus) et du ray-grass de type Westerworlds (Lolium westerwoldicum) comme plantes associées pendant trois ans (de 1998 à 2000) à trois endroits de la Saskatchewan : Swift Current (sols bruns), Saskatoon (sols brun foncé) et Nipawin (sols gris foncé). Ils ont aussi comparé troi...