We studied the effects of aboveground biomass (vegetative shoots) of 6-cultivars of Festuca arundinacea, Festuca ovina and Festuca rubra on growth of other lawn grasses. The shoots were cut and left in the field and determined their effects on the initial growth, root length and seedling height of other lawn grass cultivars-acceptors. The allelopathic properties of donors were assessed in pot culture. The flavonoids and phenolics acids contents were determined in plant samples of each test variety. The F. ovina variety „Pintor? and F. rubra „Olivia? exhibited the highest allelopathic potential. Allelopathic potential of test cultivars depended on the flavonoids and phenolic acids contents in their leaves. Their highest contents were found in leaves of F. rubra cultivar „Olivia?; the highest contents of phenolic acids were found in leaves of cultivars F. ovina „Pintor?, F. rubra „Areta? and „Olivia? and lowest in the leaves of F. ovina „Espro?. Leaving the cut biomass on the lawn surface should be discouraged, because of its adverse effects on the acceptor plants growth. There was no fertiliser effect of cut biomass left in the lawn.