Effect of auxin rate, basal wounding, auxin application method, and substrate on propagation of sweetbay magnolia, Magnolia virginiana L.

Authors: RYALS, JENNY - Mississippi State University; BOWDEN, ANTHONY - Mississippi State University; KNIGHT, PATRICIA - Mississippi State University; LANGLOIS, SCOTT - Mississippi State University; COKER, CHRISTINE - Mississippi State University; DRACKETT, PATRICIA - Mississippi State University

Submitted to: Native Plants Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2023
Publication Date: 9/21/2023
Citation: Ryals, J., Bowden, A., Knight, P., Langlois, S., Coker, C., Drackett, P. 2023. Effect of auxin rate, basal wounding, auxin application method, and substrate on propagation of sweetbay magnolia, Magnolia virginiana L.. Native Plants Journal. 24(3):225–232. https://doi.org/10.3368/npj.24.3.225.
DOI: https://doi.org/10.3368/npj.24.3.225

Interpretive Summary: Sweetbay magnolia is one of our native U.S. magnolias. There are few cultivars available in the nursery trade. Much of the commercial propagation is via seed. Development and marketing of cultivars with desirable landscape traits requires development of reliable cutting propagation techniques. This research indicates that dipping sweetbay magnolia cuttings into Hortus IBA solutions at rates of 5000, 7500, or 10000 ppm produced adequately rooted cuttings. Basal wounding of cuttings was not necessary. In an additional study, using a propagation medium of 100% pine bark combined with 10000 ppm Hortus IBA resulted in the highest quality liner.

Technical Abstract: Success of propagating sweetbay magnolia (Magnolia virginiana L. [Magnoliaceae]) from cuttings varies considerably. Results presented in the literature are generally conflicting as to which hormone type, concentration, or combination of concentrations and types work best. With labor shortages and labor costs on the rise, growers are looking at more efficient and economical ways to apply auxin. With potential to reduce production costs and increase efficiency, foliar auxin application is a novel and financially viable application method for the nursery and greenhouse industry. Two studies were conducted to assess the best way to propagate sweetbay magnolia commercially using stem cuttings. The first study examined basal wounding and auxin use as methods to improve rooting of sweetbay cuttings. Overall, dipping sweetbay magnolia cuttings in Hortus IBA at 5000, 7500, or 10,000 ppm, regardless of basal wounding, resulted in a higher quality liner. The second study investigated auxin application method and propagation substrate for further improvement of rooting success. Results indicated that sweetbay magnolia cuttings propagated into 100% pine bark with Hortus IBA at 10,000 ppm applied as a basal quick dip resulted in a higher quality liner. While foliar sprays may have the potential to reduce labor cost when propagating some plant species from cuttings, this method was not the most effective in successful cutting propagation of sweetbay magnolias. Overall, sweetbay magnolias rooted best in 100% pine bark after being dipped in 10,000 ppm Hortus IBA.