Improving rooting of Lobostemon fruticosus L. cuttings with delayed auxin treatment

• Lobostemon fruticosus can be propagated vegetatively using basal stem cuttings.
• Delayed auxin treatment promoted adventitious roots and callus formation on basal stem cuttings of L. fruticosus.
• Delaying auxin treatment stimulated the vascular cambium of L. fruticosus stem cuttings to produce callus tissue.

Lobostemon fruticosus is a semi-woody shrub used medicinally for treating wounds, blood poisoning, ringworms, skin diseases and syphilis. The material used is mostly wild harvested, leading to decline in natural populations. Propagation and cultivation methods to establish commercial production can assist in conservation of the species. The objective of this study was to determine the effect of delaying rooting hormone application on the success of vegetative propagation of L. fruticosus using basal stem cutting, cut at an angle of 30° at the base. It was done in a mist bed at the Agricultural Research Council-Vegetable and Ornamental Plant Institute (ARC-VOPI) (Pretoria, South Africa) in a factorial randomized complete block design with two growth media (cocopeat and cocopeat + potting soil1:1; v/v), rooting hormone (Seradix No. 1 and control) and six application times, with five replications. The parameters assessed were callus development, rooting percentage, shoot and root length, survival rate and stem cutting anatomical analysis. Rooting percentage significantly increased with delaying the application of rooting hormone for one to two weeks from planting, as compared to the control (without hormone) and hormone application at the time of planting (week zero). Cocopeat medium gave the highest rooting percentage (67.1%) and lowest mortality rate (18%), whereas potting soil + cocopeat medium gave the lowest root development (31.5%). Anatomical observations in this study showed that with delayed auxin application up to two weeks after planting, the callus tissue started to develop from the vascular cambium close to the cut end of the cutting. Parenchyma gaps in the phloem fiber ring close to the cut end of the cuttings was also observed. This study concludes that delaying hormone application for two weeks after planting improved rooting of L. fruticosus cuttings.