Effects of day-length, radiation, flower thinning and growth regulators on flowering of the vine cacti Hylocereus undatus and Selenicereus megalanthus

To obtain out-of-season cropping and flowering of the tropical vine cacti Selenicereus megalanthus and Hylocereus undatus, the following agricultural manipulations were tested: photoperiodic light applied for 3, 6 or 9 h after sunset; shading (to produce 80%, 60% or 40% of sunlight); flower thinning (when buds were 2-5 cm, 15-25 cm or at anthesis, or by not pollinating the flowers); or separate application of the following growth regulators [N-(2-chloro-4- pyridinyl)-N-phenylurea (CPPU); gibberellic acid (GA₃); a commercial mixture of gibberellins (GA₄ and GA₇) with benzyladenine (BA) known as Perlan™; paclobutrazol (PBZ); or ethephon (Ethrel™)]. Photoperiod and radiation did not alter the pattern of flowering. Maximum flower yields were obtained under 60% sunlight for H. undatus and under 60% or 40% sunlight for S. megalanthus. Removal of young flower buds delayed flowering and late cropping in H. undatus, but with no loss in total flower yield. In both species, CPPU promoted precocious flowering and, in H. undatus, it increased total flower yield, whereas GA₃ delayed flowering and decreased total flower yield. Hence, CPPU can be used to obtain early fruit production, and GA₃ or flower thinning (in H. undatus), to delay cropping.