Effects of Synthetic and Natural Root-Promoting Substances on Adventitious Rooting of Syzygium campanulatum Korth. Softwood Cuttings

Syzygium campanulatum Korth., commonly known as Christina is an ornamental shrub widely used in landscape horticulture. Its propagation through stem cuttings is limited by low rooting efficiency and prolonged root initiation. This study evaluated the effects of synthetic and natural root-promoting substances on adventitious rooting in softwood cuttings. A pot experiment was conducted following a completely randomized design (CRD) with 12 treatments and three replicates. Treatments included a synthetic auxin (indole-3-butyric acid, IBA), natural biostimulants (aloe vera gel, aloe vera pieces, bee honey, cinnamon powder, aspirin solution, and coconut water), combinations of selected natural substances, and water-only control. The rooting medium was a sterilized mixture of river sand and coir dust (2:1 v/v). The highest survival (92.3%) and rooting percentage (66.7%) were recorded in IBA-treated cuttings, followed by aloe vera pieces (83.3% survival; 33.3% rooting). The synthetic auxin IBA significantly outperformed other treatments in terms of root number, total root length, and fresh root biomass. Among natural substances, aloe vera pieces were the most effective, even though they were inferior to IBA. The coconut water–based combinations promoted high callus elongation, while only callus formation occurred in other treatments. Cost analysis showed that aloe vera pieces (LKR 6.50 per surviving cutting) were more economical than IBA (LKR 7.87 per surviving cutting). These results indicate that IBA is the most effective rooting agent, while aloe vera pieces offer a cost-effective natural alternative. Further research is recommended to optimize concentrations, application methods, and combinations of natural substances and to evaluate their effectiveness under varying environmental conditions.