The aim of this paper was to evaluate winterhardiness of different cultivars of Lolium perenne L. in pasture and meadow swards on peat-muck soil. The studies were carried out over 1996-2000 in two parallel experiments. Five Polish cultivars, one Polish line and three Dutch cultivars of Lolium perenne L. were involved in eleven mixtures. The cultivars of Lolium perenne L. constituted 35% of the mixtures tested and the other 65% was made up by Dactylis glomerata L., Phleum pratense L. and Trifolium repens L.; also additionally in meadow mixtures – by Trifolium pratense L. The sward species composition was determined by the botanical-and-gravimetric analysis. Winterhardiness of Lolium perenne was limited by unfavorable thermal conditions during winters, especially when used for hay production, however over the vegetation period it was followed by a fast regeneration. Mean share of Lolium perenne L. in pasture sward ranged from 45.6 to 57.8% and in meadow sward – from 24.2 to 45%. The results obtained confirm a high meadow applicability of most of the perennial ryegrass cultivars investigated on peat-muck soils of Eastern Poland and of some cultivars also to be used for hay production.

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