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.

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.

Background: For the cultivation of hemp ( Cannabis sativa L.), topping (the removal of the apical meristem) is a key cultivation practice, affecting plant morphology, physiological function, biomass allocation, and the yield of inflorescences and cannabinoids. The present study investigated the effect of topping on two monoecious industrial hemp cultivars (‘Enectaliana’ and ‘Santhica 70’). Methods: The experiment was conducted from April to June 2024 in a greenhouse using 10 L pots, following a completely randomized design with four treatments: no topping and topping above the 4th, 5th, and 6th node from the base of the main stem. During the experimental period, the mean daily air temperature was 26.0 °C and the mean relative humidity was 54.4%. Agronomic and physiological growth characteristics, biomass production, and cannabidiol (CBD) and cannabigerol (CBG) yield were evaluated. Cannabinoid analysis of the female inflorescence extracts was performed using liquid chromatography coupled with mass spectrometry (LC-MS). Results: The results showed that topping caused a significant reduction in plant height and an increase in the length of secondary shoots, with a stronger effect observed in the cultivar ‘Santhica 70’. The diameter of the main shoot was not significantly affected by the topping treatment. Topping led to a significant increase in both fresh and dry biomass, with the highest values recorded in plants topped above the 4th and 5th nodes. Regarding physiological parameters, topping at the 4th node was associated with an increased photosynthetic rate, transpiration rate, and stomatal conductance. Regarding cannabinoid composition, an increase in CBD content was observed in ‘Enectaliana’ and in CBG content, in ‘Santhica 70’, indicating that topping may act as a morphogenetic and physiological stress factor that enhances the biosynthesis of secondary metabolites. Conclusions: Topping significantly altered plant architecture, suppressing height and promoting branching, which increased biomass, particularly at the 4th and 5th nodes. These morphological changes were accompanied by enhanced physiological performance and secondary metabolism, elevating CBD in ‘Enectaliana’ and CBG in ‘Santhica 70’. Therefore, topping at the 4th or 5th node is recommended to maximize yield and phytochemical quality. Trial registration: Not applicable.