AbstractStable hybrids were produced between tetraploid perennial and Italian ryegrasses derived from commercial varieties and germplasm introduced from European collections. Spaced plant characteristics were used to select Fl plants for the production of F2 families which were assessed in small plots for growth and quality traits. Ten of the 19 selected hybrid families were based on perennial ryegrass collected from the Zurich Uplands. The influence of this parental material in improving vegetative growth during early spring, late summer and autumn was demonstrated. Its use in improving feeding value by increasing the water‐soluble carbohydrate content of hybrids was also shown. Consequently, selected hybrid varieties based on this new genetic resource showed considerable improvements in seasonal growth and quality over the older hybrid variety Augusta and Italian ryegrass variety Rv