Seeds of two perennial ryegrass (Lolium perenne L.) cultivars (diploid ‘Bartwingo’ and tetraploid ‘Calibra’) were stored in hermetically sealed glass jars at four different temperatures (-80, -20, 10 and 20°C) for five years. After the storage period the seeds were sowed in containers filled with commercial substrate. Initial growth and development occurred under natural sunlight and manual watering to maintain optimum substrate moisture. After 60 days of vegetation plants were taken from the substrate, developed plants were counted, their roots were washed and whole plants were measured for shoot and root dry-weight and total biomass.Stems and leaves per plant were counted too. The research has revealed significant effects (p<0.01) of storage temperature, cultivar and their interaction to all of the investigated traits. When averaged over cultivars the highest values were observed upon storage temperature of -20°C for all the traits except root dry-weight which did not differ between -20 and -80°C. The lowest values of all investigated traits were observed upon storage at 20°C. When averaged over storage temperatures, diploid cultivar had greater number of stems and leaves and the tetraploid one had greater root dry-weight, shoot dry-weight and total biomass. Sjeme dva kultivara (diploidni 'Bartwingo' i tetraploidni 'Calibra') engleskog ljulja (Lolium perenne L.) je bilo uskladišteno u hermetički zatvorenim staklenkama na četiri različite temperature (-80, -20, 10 i 20°C) tijekom pet godina. Nakon razdoblja skladištenja sjeme je zasijano u kontejnere s komercijalnim supstratom. Početni rast i razvoj odvijali su se pod prirodnim svjetlom i uz ručno zalijevanje radi održavanja optimalne vlažnosti supstrata. Nakon 60 dana vegetacije razvijene biljke su uzete iz supstrata, prebrojene su, korijenje im je oprano i potom su im izmjerene suhe mase izdanka, korijena i cijelih biljčica. Izbrojan je i broj stabljika i listova po biljci. Istraživanje je pokazalo značajne učinke (p<0.01) temperature skladištenja, kultivara i njihovih interakcija na sva ispitivana svojstva. U prosjeku po kultivarima, najveće vrijednosti svojstava ustanovljene su nakon skladištenja na -20°C, osim za svojstvo suhe mase korijena koja se nije razlikovala između -20 i -80°C. Najniže vrijednosti svih ispitivanih svojstava ustanovljene su nakon skladištenja na 20°C. S obzirom na temperature skladištenja diploidni kultivar je u prosjeku imao veći broj stabljika i listova po biljci, a tetraploidni je imao veću suhu masu korijena, suhu masu izdanka i ukupnu biomasu.