Aims: To evaluate best concentration of Paclobutrazol (PBZ), a gibberellin biosynthesis inhibitor, on the growth and flowering characteristics of Dendrobium ‘TC 32’ to achieve a compact, sturdy growth habit suitable for commercial pot plant production. Study Design: The experiment utilized a Randomized Complete Block Design (RCBD). It was conducted under glasshouse conditions with 70% shade at the Floriculture Research and Development Unit (FRDU), Department of National Botanic Gardens, Peradeniya, Sri Lanka. Methodology: Two-year-old, sixty tissue-cultured plants (average height 23.25 cm) were treated with four concentrations of PBZ: 0.0 (control), 0.2, 0.4, and 0.6 mg/L (T1–T4). Growth parameters (tiller height, pseudobulb circumference, leaf production and tiller production) were monitored from November 2023 to October 2025. Floral quality (flower count and spike height) was recorded bi-weekly following spike initiation in May 2024. Results: Higher concentrations of PBZ significantly influenced plant architecture (P 0.05) Conclusion: Paclobutrazol effectively induces dwarfism and increases pseudobulb robustness in Dendrobium orchids. To balance growth retardation with overall plant vigor, T2 (0.2 mg/L) is recommended as the most suitable concentration for producing high-quality, compact flowering Dendrobium ‘TC 32’ under local glasshouse conditions in Sri Lanka.
Warigajeshta et al. (Thu,) studied this question.