LOGAN, UT--In the semiarid to arid high desert landscape of the intermountain western United States, continued population growth means higher demands on the area's limited water resources. Studies showing that 50% to 60% of the region's municipal water is used for urban landscaping have prompted researchers to find ways to conserve landscape water--especially important during the region’s drought periods. Long-term conservation efforts for the high desert region rely on identification of landscaping strategies that use less water, including hardscaping, improved irrigation scheduling, and the use of drought-tolerant plants.
A new study from scientists at Utah State University says that, although deciduous trees are considered to be essential elements in high desert urban landscapes, few species can tolerate the region's drought, extreme cold temperatures, and alkaline soils. Researchers are working to identify more species of native trees that are drought tolerant, cold hardy, and resistant to insects and diseases. "Aesthetic traits such as small size, unique forms, moderate growth rate, and red fall foliage are also highly desirable in the region," the authors noted. The native bigtooth maple tree meets these desirable environmental and aesthetic criteria.
Bigtooth maple (Acer grandidentatum) is native to 10 western states with a large population found throughout northern Utah and southern Idaho. Its small size, form, and striking fall color make it a natural choice for use in water-conserving western landscapes. "Bigtooth maple has a wide range of forms and fall foliage colors, and while susceptible to a number of disease and insect pests, none appear debilitating enough to reduce the potential for its use as a landscape tree," explained Larry Rupp, Professor of Ornamental Horticulture at Utah State University and corresponding author of the report published in HortTechnology. Despite its many desirable qualities, however, bigtooth maple is uncommon in the nursery trade and urban landscapes. "Given the common use of native trees such as quaking aspen in western landscapes, it is difficult to postulate why bigtooth maple is not used more," Rupp said. "One possibility may be that the trees are propagated by seed and the resulting genetic diversity of color, size, and especially form make it difficult to market seedling plants."
Rupp and colleagues Melody Reed Richards, Roger Kjelgren, and V. Philip Rasmussen used remote sensing of tree fall color to identify potential cultivars of bigtooth maple to use in assessments as commercial candidate selections. They designed follow-up experiments to determine optimal seasonal timing of chip budding of wild bigtooth maples in northern Utah for nursery establishment.
In the study, superior accessions of bigtooth maple were selected based primarily on red fall color. Aerial digital images taken during peak fall color in 2 years were synchronized with flight global positioning system (GPS) track files using digital image editor software and visually compared with corresponding satellite images to locate the selected trees on the ground. "There are several effective ways to select native trees with landscaping potential," Rupp said. "Word of mouth is obviously a very effective means of selection. Aerial photography can also be effective, especially when selecting for a highly visible trait such as red fall color."
From the first 56 trees identified, six were selected for propagation. "We found that while some aerially selected trees were unacceptable, there were often better trees in the immediate vicinity that were overlooked from the air, suggesting that aerial photography might also be used as a means of narrowing down the search area, rather than finding specific trees," explained Rupp.
The team then conducted a series of four experiments to determine the optimum date for chip budding. The time-course experiments showed that the optimum time for chip budding scions of wild accessions in northern Utah was July through mid-August. The results showed that a reasonable window of opportunity exists for successful budding of wild bigtooth maples in northern Utah.
The authors recommend that future research studies be done to determine the capacity of bigtooth maples for commercial propagation and production, as well as their performance in constructed landscapes.
The complete study and abstract are available on the ASHS HortTechnology electronic journal web site: http://horttech.ashspublications.org/content/22/5/669.abstract
Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org
Selection and Budding Propagation of Native Bigtooth Maple for Water-conserving Landscapes
Melody Reed Richards, Larry A. Rupp, Roger Kjelgren, and V. Philip Rasmussen
HortTechnology 22:669–676. [Abstract][Full Text][PDF]