PRECOCIOUS FLOWERING OF ARIZONA CYPRESS WITH GIBBERELLIN

Abstract

Extremely early flowering (production of staminate strobili 88 days from germination) of Arizona cypress (Cupressus arizonica Greene) was obtained with foliar application of gibberellin A 3 commencing at age 55 days. Trials with differing concentrations of gibberellin at various ages indicated that flower bud differentiation depends on both age and gibberellin concentration, younger seedlings requiring more exogenous gibberellin. Simultaneous application of two growth retardants (AMO-1618 and B-995) had no effect upon the number of flowers, but flower size was increased where B-995 and gibberellin were given together. The period of time between initial spraying and first visible appearance of staminate strobili is 23 to 25 days. On most plants 60 to 80% of the growing vegetative meristems are changed into flower buds within 60 days of the initial treatment, often resulting in over 500 flower buds on one plant. The pollen is viable.