Optimizing Rooting and Growth of Salvia rosmarinus Cuttings in Soilless Systems Affected by Growth Regulators

TL;DR

This study explores how different propagation systems and growth regulators affect the rooting and growth of rosemary cuttings, offering practical guidelines for commercial nurseries.

Contribution

The study identifies optimal combinations of propagation systems, hormone types, and growth regulator concentrations for rosemary cuttings.

Findings

The float system with powder hormone and no retardants achieved the highest shoot height (16.7 cm).

Aeroponics with powder hormone and daminozide 1000 ppm promoted the most root branching (12.2 lateral roots per cutting).

High doses of growth regulators negatively impacted all growth parameters across systems.

Abstract

This study investigated how propagation systems, growth regulators, and hormone formulations interactively affect the rooting and subsequent growth of rosemary (Salvia rosmarinus Spenn) cuttings. A three factorial (3 × 2 × 7) experiment was conducted under a fully controlled greenhouse environment, incorporating three soilless propagation systems (mist, float, aeroponics), two rooting hormone formulations (powder and gel-based IBA), and two growth regulators (paclobutrazol and daminozide) at three concentrations each. Significant differences (p < 0.001) were found in shoot height, root length, and number of lateral roots. The float system combined with powder hormone and no retardants achieved the highest shoot height (mean = 16.7 cm), while aeroponics with powder hormone and daminozide 1000 ppm promoted the greatest root branching (mean = 12.2 lateral roots per cutting). Root length was maximized (mean = 15.9 cm) under float systems with daminozide 1000 ppm. High doses of both growth regulators negatively affected all parameters across systems. Post-transplantation monitoring confirmed that cuttings from float and mist systems treated with powder hormone and low or no growth retardants exhibited superior establishment and net growth over 60 days. These findings demonstrate the critical importance of pairing hormone type, regulator concentration, and propagation system, providing actionable protocols for nursery managers aiming to enhance Salvia rosmarinus propagation in commercial practice.

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