Paclobutrazol retards vegetative growth in hydroponically-cultured Leonotis leonurus (L.) R.Br. Lamiaceae for a multipurpose flowering potted plant

• Paclobutrazol at 2 mg a.i.
• retards growth of Leonotis leonurus
• unveils a potted flowering plant

Leonotis leonurus (L.) R.Br.; Lamiaceae is an indigenous southern African plant of commercial interest, which grows up to 3 m tall and 1.5 m wide, thus making it difficult to cultivate for the potted flowering plant industry. We tested different rates of a growth retardant paclobutrazol for retarding vegetative growth of L. leonurus for use as a flowering potted plant. The aim of the study was to determine the ideal rate of paclobutrazol from treatments of 0 (control), 2, 4, 8 and 16 mg active ingredient (a.i.) per plant applied to rooted cuttings of 8 ± 0.5 cm in height. Plants which received 2 mg a.i. were marginally shorter than the untreated control, while those treated with 4, 8, and 16 mg a.i of paclobutrazol were greatly dwarfed. Plants treated with 4, 8 and 16 mg a.i of paclobutrazol were seriously stunted, rosette, with senescing leaves and low fresh and dry weights. The concentration of 4 mg a.i caused the largest dwarfing with plants in this treatment only weighing 32% of the total fresh weight of the control and 31% of the total dry weight of the control plants. We therefore recommend the application of as little as 2 mg a.i. of paclobutrazol as an alternative way of chemically inducing dwarfing in L. leonurus, for producing flowering potted plants.