Effect of Indole-3-Butyric Acid and A-Naphthaleneacetic Acid on Rooting of Bottle Brush [Callistemon lanceolatus (Sm.) Sweet] Cuttings

Background: Callistemon lanceolatus (bottle brush) is a popular woody ornamental tree valued for its bright inflorescences and adaptability to urban landscapes. However, propagation through cuttings is limited by poor rooting and delayed establishment. This study evaluated the effect of cutting type and auxin concentration on root and shoot development in C. lanceolatus to enhance clonal propagation efficiency. Methods: The experiment was conducted (April 2024 - May 2025) at VISTAS, Chennai, using a factorial completely randomized design (FCRD). Hardwood, semi-hardwood and cuttings formed in the previous season (CFPS) were treated with IBA (1000, 1500, 2000 mg L-1) and NAA (500, 1000, 1500 mg L-1), along with a control. Cuttings were planted in sterilized sand under mist chamber conditions (28-32°C; 80-90% RH). Data on rooting percentage, number of roots, root length and shoot growth were analysed statistically. Result: Significant variations were observed among treatments. CFPS treated with 1000 mg L-1 IBA showed the highest rooting (88.5%), maximum roots (15.6), root length (23.9 cm) and shoot length (20.8 cm), outperforming all other combinations. IBA proved more effective than NAA and moderate concentrations were superior to higher levels. The study concludes that CFPS with 1000 mg L-1 IBA provides optimum rooting and sprouting, offering a simple and reliable method for vegetative propagation of Callistemon lanceolatus.