Clonal Propagation of Stem Cuttings of Spigelia Marilandica, S. Gentianoides Var. Alabamensis, and S. Marilandica × S. Gentianoides Var. Alabamensis F2 and F3 Hybrids

New clonally propagated ornamental cultivars must display high levels of rooting success in order to be commercially viable. Spigelia marilandica (L.) and S. gentianoides Chapm. ex A. DC. var. alabamensis K. Gould are species endemic to the southeastern United States that show potential for development of cultivars for landscape use. The objectives of this study were to determine whether cutting date, indole-3-butyric acid (IBA) level, and genotype impacted rooting percentage, root number, and root length in Spigelia. Stem cuttings were obtained from five genotypes of S. marilandica (SM), one genotype of S. gentianoides var. alabamensis (SGA), three genotypes of SM × SGA F₂ hybrids, and two genotypes of SM × SGA F₃ hybrids. IBA level significantly affected rooting percentage and root number, but not root length of the genotypes. The SM × SGA F₂ and F₃ hybrids successfully rooted through all months evaluated, while SM and SGA genotypes exhibited a decline in rooting in cuttings taken in September. Results suggest that SM and SGA may be successfully propagated by treating stem cuttings taken in May, June, July, or August with 0.3% IBA. Cuttings of SM × SGA hybrids can be taken through September. These protocols provide a basis for rapid propagation of Spigelia and may provide a foundation for other species and hybrids within the genus.