Auxin Concentration Affects Adventitious Rooting of Mound Layered Caddo Sugar Maple (Acer saccharum) and Shantung Maple (Acer truncatum)

Stump sprouts of stooled caddo sugar maple (Acer saccharum Marsh. subsp. saccharum) (caddo maple) and shantung maple (A. truncatum Bunge) were propagated by mound layering. In early summer, shoot bases were wounded and treated with 0, 10,000, 15,000, or 20,000 ppm (0, 1.0, 1.5, or 2.0%) indole-3-butyric acid (IBA) dissolved in 50% ethanol or 0, 5,000, or 10,000 ppm (0, 0.5, or 1.0%) of the potassium (K) salt of IBA (K-IBA) dissolved in water. Shoot bases were covered with a commercial growing substrate containing bark, Sphagnum peat moss, and perlite and retained by plastic rings 38 cm (15 in) in height. Rooted shoots were harvested in fall or late winter. Auxin concentration influenced rooting of caddo maple and shantung maple mound-layered shoots. Rooting peaked at 15,000 ppm (1.5%) IBA for both caddo maple (71%) and shantung maple (34%). Mean root number for caddo maple, but not shantung maple, increased as IBA concentration increased. Differences in mean root length were not significant. Results suggest caddo maple can be successfully propagated by mound layering. For shantung maple propagation, mound layering was less successful, so alternatives such as stem cuttings should be considered.