Effects of Growth Regulators and Propagation Systems on the Growth of Lavender (Lavandula angustifolia) Cuttings

This study evaluated the effects of the growth retardants daminozide and paclobutrazol on the production of propagation material of Lavandula angustifolia under controlled greenhouse conditions. Cuttings were propagated using three systems (mist, aeroponics, and float) combined with growth regulator treatments and two rooting hormone formulations (powder vs. gel). Shoot height and root traits were assessed as indicators of propagation performance. The results are reported as estimated marginal means (±SE) derived from a fitted general linear model. Overall, the float system was associated with greater shoot elongation, whereas aeroponics consistently promoted longer and more highly branched root systems, resulting in the highest root length and branching among the three propagation systems. Compared with mist and float systems, aeroponic propagation was associated with approximately 20–30% higher estimated root length and a consistently greater degree of root branching across growth regulator treatments. Gel-based rooting formulations further enhanced root length and branching compared with powder formulations across propagation systems. Growth regulator treatments generally reduced shoot height relative to controls, while daminozide showed system-dependent trends for shoot and root traits.