Forcing Irradiance, Temperature, and Fertilization Affect Quality of `Gloria' Azalea

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  • 1 Environmental Horticulture Department, University of Florida, Gainesville, FL 32611

Dormant-budded `Gloria' azaleas (Rhododendron sp.) were used to observe the effect of forcing irradiance, temperature, and fertilization on postproduction performance after flower bud dormancy had been broken. Four experiments were conducted during forcing, the treatments for each experiment were: Expt. 1, three forcing irradiances (200,460, and 900 μmol·m-2·s-1) and three postproduction irradiances (4, 8, and 16 μmol·m-z·s-1); Expt. 2, three forcing irradiances (320, 560, and 1110 μmol·m-2s-l); Expt. 3, three controlled day/night temperatures (18/16C, 23/21C, and 29/27C); Expt. 4, fertilizer applied for 7, 14, or 28 days at either 150 or 300 mg N/liter (12% nitrate, 8% ammoniacal) 20N-4.8P-16K soluble fertilizer at every watering, control plants did not receive fertilizer. Days to harvest (time until plants had eight individual open flowers) was less at the high forcing irradiances and temperatures and when fertilizer was applied during forcing. Flower color was less intense at the low forcing irradiance levels, high temperatures, and when duration of fertilization was prolonged and concentration was high. There were more open flower inflorescences at week 2 of postproduction at high forcing irradiance levels, but their number was not affected by forcing temperature or fertilization. Postproduction longevity was shorter when forcing was at 29/27C (day/night) and when plants were fertilized for 28 days at 300 mg N/liter, but was not affected by forcing or postproduction irradiance.

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