The effects of GA3 (25 or 100 mg×liter-1) canopy sprays applied to Hass avocado (Persea americana Mill.) trees in a commercial orchard in the months preceding an “off” or “on” bloom year on inflorescence and vegetative shoot number and yield were quantified. GA3 (100 mg×liter-1) applied in September (early stage of inflorescence initiation) reduced inflorescences number both years, but not yield. GA3 (25 or 100 mg×liter-1) applied in November (early stage of inflorescence development) before the “on” bloom reduced inflorescence number with a concomitant increase in vegetative shoot number and a 47 % yield reduction. GA3 in January (initial development of the perianth of apical flowers) or March (cauliflower stage of inflorescence development) caused precocious development of the vegetative shoot apex of indeterminate inflorescences, but had no effect on inflorescence or shoot number either year. GA3 (25 mg×liter-1) applied in March of an “off” bloom year increased production (2-fold) of commercially valuable fruit (213-269 g per fruit) and delayed skin blackening. This paper provides basic information that can be used to develop strategies for manipulating yield and evening out alternate bearing in avocado.

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