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- Author or Editor: Robert Dalgleish x
Three rose cultivars, Ilona, Mercedes, Sonia, on Rosa multiflora rootstock were grown in a nutrient film technique (NFT) system for 2 years, with root-zone warming (RZW) to 25°C compared with ambient temperature roots. In the 1st season the night air temperatures were 18°, 12°, and no heating (9°); in the 2nd season, 18°, 14°, and 10°. Harvested flowers were graded according to stem length. In the 1st winter seasons RZW increased the proportion of long stemmed roses and increased the total yield, especially in ‘Ilona’. In the 2nd winter season, RZW again increased the proportion of long stemmed roses in ‘Ilona’ but increased the total number of blooms more in the other cultivars. The effects of RZW persisted into the summer period. Prevailing wholesale prices were used to calculate probable gross returns based on yields. Since RZW tended to give longer stemmed roses and more blooms than did ambient conditions, this treatment enhanced returns more than that of the increased air temperature treatments. RZW increased probable returns over the ambient for ‘Ilona’, ‘Mercedes’, and ‘Sonia’ by 49%, 69%, and 78%, respectively.