Development of a Rooting Protocol for Oenothera Spp. Vegetative Cuttings

Oenothera is a genus of brightly colored and phenotypically diverse flowers collectively known as evening primroses. This genus has seen limited cultivar development in commercial horticulture. By inducing genetic diversity through chemical mutation and hybridization, desirable traits can be produced. If a program for production of desirable mutant and hybrid cultivars is to be successful, a protocol for vegetative replication must be attained. When desirable evening primrose individuals are isolated, replication through stem cutting propagation is necessary. An experiment was devised to determine the best rooting media and hormone treatment for root initiation of Oenothera spp. Cuttings were taken from O. speciosa Nuttall and O. missouriensis Hooker. These 14-cm stem segments were put in 98-cell plug trays using either coarse perlite or fine vermiculite. For each media type, three commercially available formulations of indole butyric acid (IBA) were applied at a rate of 1000 ppm. The IBA products included Hortus® water-soluble salts, Dip’nGrow® liquid concentrate, and Hormex® rooting powder. Each treatment also contained a control group of untreated cuttings. Trays were then placed under intermittent mist irrigation set at 8 seconds every 2 minutes until root data was recorded 8 days later for O. speciosa and 2 weeks later for O. drummondii. Results showed a significantly higher average rooting percentage, number of roots, and root length for the vermiculite rooted cuttings. Indole butyric acid treatments had varying results among the media types and two species, as the hormone treatment did not have significantly greater rooting percentages than the control for O. speciosa. No significant difference was found between the IBA products alone, but an interaction was detected using Dip’nGrow for root length and Hortus® for number of roots using vermiculite for O. drummondii.