Bigtooth or canyon maple is a small tree native to the intermountain western United States and possesses characteristics valued by the nursery and landscape industries (Barker, 1974; Kuhns, 2003; Tankersley and Emino, 1980), including a deciduous habit (Eastmond, 1968), adaptability to a wide range of temperatures (−30 to 100 °F) (Kuhns, 2003), drought tolerance (15–20 inches of annual precipitation), and adaptability to a wide range of soils and habitats. It produces a winged-samara and has leaves with deep, simple, tooth-like lobes. The fall foliage ranges in color from yellow to orange to red while samaras can be green to red. Bigtooth maple exhibits a wide variety of tree forms (including columnar, pyramidal, and oval). Moreover, in its native habitat, it exhibits an even more remarkable range from single stem trees to short, multistemmed shrubs.
Bigtooth maple is uncommon in both the nursery trade and in urban landscapes, with Rocky Mountain Glow® (‘Schmidt’) being the primary cultivar and the cultivars Manzano™ and Western Torch Wasatch Maple having limited availability. Propagation of cultivars is primarily done by budding on sugar maple (Acer saccharum) rootstocks. While these budded plants have been successfully grown in Utah, there is some concern in the industry that sugar maple rootstocks are not the best option for Utah soils because of the potential for iron chlorosis with alkaline soils. Bigtooth maple is easily and commonly grown from seed for reclamation, but the genetic diversity in color, size, and especially growth habit make it difficult to market seedling plants as performing within known parameters. With the exception of budding, vegetative propagation has been so difficult as to be commercially unfeasible (Donnelly and Yawney, 1972; Tankersley, 1981). If asexual propagation were easier to accomplish, it is reasonable to expect that superior specimens would be more readily available to the landscape industry and would provide utility in landscaping.
Past efforts in asexual propagation of bigtooth maple have resulted in limited success. Bigtooth maple propagates itself naturally by layering when lower branches come in contact with the soil and form roots (Christensen, 1962). Tankersley (1981) observed rooting on 20% of mound layered and 71% of trench layered 1-year-old maple seedlings. Although trench layering had a higher rooting percentage, it is a very labor intensive propagation technique. Micropropagation of bigtooth maple resulted in 15% rooting (Bowen-O’Connor et al., 2007) of juvenile material, but has not been shown effective in propagating mature specimens. Asexual propagation by cuttings has been even less successful with Tankersley achieving only 0.8% rooting (1981). If this plant is to be used as a landscape ornamental, methods of asexual propagation must be improved to meet the needs of the nursery and landscape industries (Bowen-O’Connor et al., 2007).
A review of past research on stem cuttings reveals that juvenility, auxins, girdling, wounding, tissue carbohydrate levels, hedging, selection of cutting material, etiolation, and/or other factors can improve rooting in hard-to-root woody species (Griffin and Bassuk, 1996; Hartmann et al., 2011; Herman and Hess, 1963; Maynard and Bassuk, 1987). It has long been known that etiolation enhances root formation and relatively recent research has shown that etiolation and banding techniques can dramatically improve rooting of many woody plants (Maynard and Bassuk, 1987). Adventitious root formation and uniformity are also increased in hard-to-root cuttings when wounded and treated with an auxin, such as IBA (Alsup et al., 2003; Griffin and Bassuk, 1996).
Propagation via cuttings is a cheap, simple, and effective method that will allow propagators to produce commercial quantities of selected specimens if it can be effective with bigtooth maple (Griffin and Bassuk, 1996). Our objective was to determine if etiolation would improve a cutting propagation system using coppiced stock plants, wounding, supplemental auxin, bottom heat, shading, and intermittent mist to increase rooting of bigtooth maple cuttings to economically acceptable levels.
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