771 PB 351 VARIATION IN FLORICULTURAL PERFORMANCE OF `GLORIA' AZALEA AFTER DORMANCY-BREAKING TEMPERATURE TREATMENTS

in HortScience

Commercially-produced, endodormant `Gloria' azaleas were placed into temperature × duration dormancy-breaking treatments at 2 month intervals to characterize seasonal variation in floricultural performance. Given the standard industry practice to break bud dormancy is 6 weeks at 3.5 to 7.2 C, three temperatures (3.5, 7.5, 11.5 C) and four durations (2, 4, 6, 8 weeks), plus a non-chilled control, were used to examine the contribution of each dormancy-breaking factor to subsequent floricultural quality. Treatment-Induced leaf abscission and flowering were quantitated, including days to Initial flowering and 50% flowering. Flowering response of dormant-budded azaleas produced during late spring and early summer (chilled during summer and early fall, respectively) was primarily and positively related to chilling duration, with only a minor influence of chilling temperature. In contrast, flowering of fall-produced endodormant plants (chilled during late fall) was best at 3.5 C, regardless of duration. Across all intervals, control plants averaged a leaf loss rate of 3 to 4 per day, suggesting a steady-state turnover rate. While leaf abscission was higher in all chilling-treated plants, those produced during fall and given the standard (or longer) chilling treatment exhibited about twice the total abscission (averaging as much as 20 leaves per day) as plants produced at other times, resulting in a clear reduction in plant foliar quality.

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