The proportion of spurs flowering on apple trees (Malus domestica Borkh. cv Golden Delicious) displaying a high degree of alternate-year flowering was increased in the off year by gibberellin A₄ (GA₄) and C-3 epi-GA₄ applied in the previous year. When applied 4.5 weeks after anthesis amounts of GA₄ ranging from 3 to 300 g per spur and 25 or 50 g of C-3 epi-GA₄ per spur were effective. Treatments with GA₄ made seven weeks after anthesis were less effective. A combination of 30 g GA₄ and 30 g zeatin (6-(4-hydroxy-3-methylbut-trans-2-enylamino)purine) promoted flowering at both treatment times, and tended to be more effective than GA₄ alone.