Effects of cutting time, cutting position and auxin application on rooting of stem cuttings of lemon verbena (Lippia citriodora (Palau) Kunth)

Lemonverbena(Lippia citriodora (Palau) Kunth) is a medicinal plant belonging to the Verbenaceae family. Propagation of lemon verbena is commonly performed using stem cutting. In order to study the effects of cutting time (autumn, winter and spring), cutting position (apical, medial and basal) and different concentrations of indole butyric acid (ABA) (0, 2000 and 4000 ppm) on rooting of stem cuttings of lemon verbena, a factorial experiment based on a three-replicated completely randomized design was performed in a greenhouse in Kavar (Fars province) in 2016-2017. According to the results, the autumn taken cuttings showed better rooting compared with both winter and spring taken cuttings. Regardless of auxin application and cutting time, the highest rooting percentage, root number, root dry weight and shoot length were observed in the basal cuttings of larger diameters. The medial cuttings showed higher rooting percentage than apical ones. The rooting-related characteristics including rooting percentage, root number, and dry weight improved as the concentration of IBA increased up to 2000 ppm. While at the highest concentration of IBA (4000 ppm), most rooting-related characteristics showed no significant increase in comparison to 2000 ppm, the length of the newly emerged shoots on cuttings decreased.