2018 ASHS Annual Conference

Crape myrtles provide a reliable source of color for many southern landscapes, often flowering for more than 100 days. Mississippi State University has released six new crape myrtle selections, including Shumaka™. Shumaka™ is a hybrid resulting from the cross of Lagerstroemia ‘Arapaho’ and an unknown pollen donor. Shumaka™ has a unique very light pink flower color and large growth habit. Three-year-old plants in a research setting are 20+ feet and have flowered from early June through late August. The bark is smooth to exfoliating, with outer bark that is grayish brown in color. The objective of this research was to evaluate ease of rooting and determine optimal commercial auxin formulation and concentration for hardwood cutting propagation of Shumaka™. Five-inch (12.7-cm) medial cuttings were harvested from the parent plant and inserted to a depth of 1 inch (2.5 cm) in propagation medium on 1 Feb. 2017. Propagation medium was 100% perlite placed in 3-inch (7.6-cm) containers. Treatments included two basal wounding treatments (wounded or non-wounded), three auxin formulations [Hortus IBA (Hortus IBA Water Soluble Salts™), Dip’N Grow® (IBA + NAA at 50% the rate of IBA), or Hortus IBA + KNAA (Hortus IBA Water Soluble Salts™ + NAA potassium salt at 50% the rate of IBA)], and three levels of auxin (0, 1000, or 5000 ppm IBA). Data collected after 60 days included rooting percentage, growth index (new shoots), cutting quality (0-5, with 0 = dead and 5 = transplant-ready cutting), total root number, average root length (of three longest roots), and root quality (0-5, with 0=no roots and 5=healthy, vigorous root system). Results showed that rooting percentage, number of roots, average length of the three longest roots, and growth indices were similar among treatment combinations. No benefits were observed from wounding of the cutting. Cuttings dipped in Hortus IBA did have better root quality compared to cuttings dipped in DNG; when Hortus IBA concentration was increased, root and cutting quality and root number increased. Overall, the results suggested that dipping Shumaka™ hardwood cuttings in Hortus IBA at 5000 ppm resulted in a higher quality liner.