IBA and Some IBA-Synergist Increases of Root Regeneration of Landscape-Size and Seedling Trees

Abstract

Sprays of 3000 ppm indole-3-butyric acid (IBA) onto the fresh-cut roots of 250-300 cm. tall, fall dug sugar maple (Acer saccharum) and red oak {Quercus rubra) held in cold storage and spring-treated, increased lateral root number. Similar treatments of spring dug sugar maple, European birch (Betula pendula), littleleaf linden (Tilia cordate) and both spring and fall dug green ash (Fraxinus pennsylvanica var lanceolata) did not increase root numbers compared to controls. The addition of auxin synergists (B-naphtol, nicotinic acid and phloroglucinol) with IBA applied to the roots of red oak and littleleaf linden increased root number compared to controls but the increase was no greater than IBA alone. The synergists had no effect on sugar maple. Dipping the roots of one year seedlings of European birch and wild plum {Prunus americana) into IBA plus e-naphtol or nicotinic acid resulted in significantly greater new leaf and root growth compared to IBA alone or controls. Several of the treatments may be commercially feasible.