The 2009 ASHS Annual Conference

Hydrangea macrophylla ‘Merritt’s Supreme’ plants were used to study the effects of foliar sprays of Def-6 (Def, 2500, 5000, 7500 and 10000ppm), giberellic acid, (GA, 50ppm), copper-EDTA (CuEDTA, 0.5% and 1.0%), Florel (F, 2000ppm) and urea (U, 3%) on defoliation in the autumn, and growth and flowering performance during forcing. Compared to controls, spraying plants with U or GA alone had no influence on defoliation or plant performance during forcing, and spraying plants with Florel alone had no influence on defoliation but decreased total flower dry weight during forcing. Combining urea with Florel sprays decreased the adverse effects of Florel on plant quality and combining GA with Florel improved defoliation. Increased concentrations of Def and CuEDTA increased defoliation. Compared to controls, plants sprayed with CuEDTA were more defoliated, had necrosis to buds and leaves, and produced less flower dry weight during forcing. Combining urea with CuEDTA sprays decreased the adverse effects of CuEDTA on plant quality. Compared to controls, spraying plants with Def increased defoliation, caused no visible damage to plants, and had no adverse effects on plant quality during forcing. Adding urea to sprays containing Def decreased or had no influence on the efficiency of defoliation and improved plant quality compared to Def alone. Adding GA to sprays containing Def increased the efficiency of defoliation without adversely influencing plant quality.