Paclobutrazol, Gibberellic Acid, and Rhizome Size Affect Growth and Flowering of Zantedeschia

Growth and flowering of Zantedeschia elliottiana W. Wats. and Z. rehmannii Engl. were studied. Rhizomes of both species were produced either in a glasshouse or outdoors in California. Plants grown from glasshouse-produced rhizomes flowered within 90 days only when a preplant rhizome soak of 500 ppm GA, was applied. Control plants of both species flowered when grown from field-produced rhizomes, but a GA 3 preplant rhizome soak significantly increased the number of flowers (spathe and spadix) produced. Paclobutrazol, applied as a preplant rhizome soak or as a soil drench when shoots were 2 to 3 cm long, significantly limited plant height of Z. rehmannii from either source if not treated with GA,. Paclobutrazol and GA, treatments interacted significantly to affect height and number of flowers of Z. rehmannii grown from field-produced rhizomes. Treatment with GA 3 overcame the dwarfing effect of paclobutrazol, while paclobutrazol treatment limited flower production. Z. rehmannii rhizomes >6.5 cm in diameter produced more shoots and leaves than smaller rhizomes, regardless of GA 3 treatment. Emergence, number of shoots, and number of leaves from Z. elliottiana were not significantly affected by the rhizome size-GA 3 variable combination. Production of normal flowers was increased by GA 3 treatment of all sizes of Z. rehmannii rhizomes except the smallest, with the most flowers being produced by plants from the largest rhizomes. Production of deformed flowers was greatest from rhizomes treated with 500 ppm GA 3 , with no deformed flowers on control plants.