Vegetative propagation of Pelargonium sidoides D.C. (Rabassam) using leaf-bud cuttings

Abstract

Pelagonium sidoides (Rabassam) is an herbaceous plant of the Geraniaceae family used throughout history as a medicine for the people of South Africa which has and recently also been exported to other parts of the world. A number of studies have shown that the plant extracts have anti-microbial, anti-viral and immune boosting properties. Consequently, it has been harvested in the wild for these properties, exposing the species to possible extinction. This scenario can be addressed by artificially mass propagating and producing the species to satisfy demand. One method of propagating the plant is to use leaf-bud cuttings. Unfortunately, vegetative propagation of the species using leaf-bud cuttings is not documented. This study was therefore conducted to investigate the influence of rooting medium (sand and sand + coir), rooting hormone (0.1% indole-butyric acid (IBA), planting depth (1.5 and 3 cm) and season (summer, autumn, winter and spring) on rooting success of leaf-bud cuttings as well as impacts of these treatments on the survival and morphological characteristics of subsequent transplants. The experiments were conducted on a mist bed in a greenhouse located at the Experimental Farm of the University of Pretoria (25o45’S, 28o16’E). A 23 factorial experiment laid out in a randomized complete block design (RCBD) with 3 replicates was carried out. Root length, root number, planting depth, growth media and hormone application, were assessed by destructive sampling at 5 to 25 days after planting (DAP). Results of the study demonstrated that sand medium, compared to a mixture of sand + coir medium, resulted in higher rooting percentage and more roots. However, sand + coir medium produced longer roots on the cuttings. Planting depth of 3 cm resulted in higher rooting percentage and better establishment of cuttings as compared to a depth of 1.5 cm. Application of the rooting hormone 0.1% IBA improved the number of roots but not rooting percentage nor root length. Rooting of cuttings was improved when propagated in autumn (longer roots) and spring (higher number of roots) than in summer or winter. After one month transplanting of cuttings, significant differences (P < 0.05) were noted in survival percentage due to the media initially used. Cuttings initially propagated on sand showed a higher survival percentage (78.6%) and had a higher number of roots, which were longer, compared to cuttings initially propagated in a medium of sand + coir (61.2%). Cuttings initially propagated in sand and treated with hormone had significantly more roots after transplanting. Application of hormone also improved root and shoot length of transplants. Based on observations, cuttings taken from younger mother stock plants had a higher chance of survival than cuttings taken from mature stock plants. In general, leaf-bud cuttings of P. sidoides can be artificially propagated without rooting hormone but the success rate will be low. The ideal regime is to propagate cuttings treated with IBA in a sand medium.