Effect of gibberellic acid spraying and soaking of rhizomes on the growth and flowering of calla lily (Zantedeschia Spreng.)

Rhizomes of Zantedeschia, 15-18 cm in circumference with leaf buds 0.5-1 cm in length, were planted into 20-cm pots on 15 May 2006 into a medium consisting of peat with a pH of 6.2, enriched with a slow-release fertiliser Osmocote Plus (3-4M) and mixed with fresh shredded pine bark at a rate of 3:1 (v:v). Before planting, the rhizomes were soaked for 20 minutes in a water solution of gibberellic acid at a concentration of 150 mg x dm-3, or sprayed with the same concentration once, twice or three times, each time after thorough drying. For each round of spraying, 100 ml of the solution were used. Gibrescol 10 MG was applied. Gibberellic acid had a similar effect, whether applied in the form of a solution for soaking or spraying of rhizomes. The number of sprayings of rhizomes had no effect on the effectiveness of gibberellic acid. In the cultivar ‘Black Magic’, rhizome spraying caused earlier flowering, while in ‘Cameo’ a similar effect was obtained by soaking the rhizomes in gibberellic acid. Gibberellic acid had no effect on the quality of flowers and the number of leaves. Gibberellic acid had a good effect on the index of leaf greenness in the cultivars under study.