RESEARCH CONCERNING THE EFFECTS OF BULB VERNALIZATION AND PLASTIC FILM COVERS ON TULIP FLOWERING
Results indicate that by gradually lengthening the cold treatment of bulbs from 15 to 60 days, a shortening of the growth cycle is induced, and the date of flowering is advanced. Moreover, as increasingly thick plastic covers are used then, starting with the uncovered control and up to 0,15 mm plastic films, the flowering date is later and less advanced. But 0,20 mm plastic films have not produced any statistically appreciable differences.
In agreement with the observations made by other authors, bulb vernalization induces a gradual improvement of qualitative characteristics, such as stem elongation and increased fresh weight of cut flowers. Conversely, plastic covers have a slight depressing effect on flowers obtained from bulbs that have undergone vernalization for 15 – 30 and 45 days respectively, but induce improved flowers from bulbs vernalized for 60 days.
With respect to flower production per unit surface area, no appreciable differences were observed either between different lengths of vernalization or between different types of plastic film covers.