Container grown photinia plants treated with 6-benzylamino purine (BA) or dikegulac (Atrinal) had 3 to 4 times as many branches as untreated plants. Branching was greatly increased by applying 10 to 15 gm (2-3 tsp) of Osmocote 18N-2.6P-10K (18-6-12) to supplement the fertilizer in the container mix. Application of Atrinal increased branching an additional 100% at the highest fertilizer level. Hand pinching the day before the first Atrinal application increased branching in one experiment, but hand pinching 11 days before the first Atrinal application had no effect on the response to Atrinal in another experiment. BA and N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (Accel) increased branching when applied with Off-Shoot-O (OSO), and had less effect or no effect without OSO. Adding a phosphate buffer (Buffer-X) to prevent precipitation of BA further increased the response to the BA plus OSO treatment.

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Author notes

Scientific Paper No. 6826. Washington State Univ. Agric. Res. Center. Project No. 0085.

2Horticulturist, retired July, 1983. The technical assistance of J.M. Wetherington is gratefully acknowledged.