Canyon Maple: A Tree for the Interior West
by Michael Kuhns, Extension Forestry Specialist
Wouldn't it be great if there was a tree-sized maple to plant in our landscapes that was native to the interior West (Rocky Mountain /Intermountain area)? What if this maple had fall color to rival a sugar maple (Acer saccharum), extreme cold tolerance, good drought resistance, tolerance of fairly high soil pH, and could even be tapped for maple syrup production? Well, such a tree does exist. It's called canyon maple or bigtooth maple (Acer grandidentatum) and it has great potential for landscape use in the West.
Canyon maple is a native of moist, mountainous sites from southeastern Idaho, throughout Utah, western Colorado, portions of Arizona and New Mexico, and scattered locations in northern Mexico, southwestern Texas, and western Oklahoma. It is especially common in Utah's Wasatch mountains, where it grows at elevations from 4,500 to 7,500 feet. It tends to grow on lower slopes and canyon bottoms in the mountains in association with Douglas-fir and junipers, but below aspen and subalpine fir.
Though canyon maple grows best on moist sites with good soils, it can do well on poorer soils and drier sites, making it a good candidate for many landscape situations. It is moderately shade tolerant and tolerant of fairly alkaline (high pH) soils. It is quite cold tolerant, with a likely minimum USDA Plant Hardiness Zone of 4 to possibly 3. It may have some problem, however, with fluctuating winter temperatures if planted at lower elevations.
Canyon maple is a small- to medium-sized tree, reaching 30 to 40 feet in height and 10 inches in trunk diameter (I think it could get larger in cultivation). It's native growth rate is fairly slow, though I have seen a tree in a yard in Logan, Utah that was about 30 feet tall and 20 years old or less. The form of native trees is variable and ranges from shrubby to a multi-stemmed tree to an upright, single-stemmed tree. The crown shape is oval to round. At this point I am not sure how much of this native tree form is genetically determined and how much is caused by environmental factors, though I suspect that most of it is environmental.
Leaves of canyon maple look much like sugar maple leaves, with three to five lobes and a dark green color. Fall color is spectacular, varying from yellow to orange to red and lasting quite a while. This fall color variation may be partly genetically controlled and partly dependent on environmental conditions.
Canyon maple is relatively free of serious insect and disease problems. It is wind-firm and strong-wooded and should stand-up well to storms. Its general toughness and durability make it a fairly long-lived tree.
Landscape Use in the Interior West
Canyon maple can be a valuable addition to our landscapes. Currently the most commonly planted maples in landscapes in the interior West are Norway maple (Acer platanoides) and silver maple (Acer saccharinum). Both trees can be good choices in the correct location, but both have their problems. Norway maple is becoming over-planted in some areas, northern Utah in particular. Silver maple grows very fast and can quickly overwhelm a landscape. It also turns yellow due to low iron or manganese availability in high pH soil. Canyon maple can be planted to add variation in our landscapes and will not have many of the problems of other non-native maples.
Canyon maple's tolerance of moderate drought, high soil pH, and cold mean that it should be usable in most landscape situations in our area. It is likely to do best and grow fastest with plenty of moisture and good soil, but it also should do fine on drier sites and rockier soils. It requires full sun or partial shade for good growth.
I have seen canyon maple effectively used as a solitary specimen tree or in a dense mass planting. Single trees grow tall and straight with a form like a Norway or sugar maple. When used in clumps or masses its form will depend on pruning. It can be developed into an effective, natural-looking hedge with occasional pruning and periodic cutting-back (renewal pruning).
Its medium size makes canyon maple a good tree for small- or large-scale residential landscapes, parks or other open areas, and street plantings where the parking strip width is at least four feet (six feet is better). If it gets enough water expect it to get as big or bigger than it does in native situations, though it shouldn't get much taller than 40 to 50 feet with a 20 to 30 foot crown spread. The growth rate of canyon maple on a good site will be adequate but not fast.
As with other trees, seed source or geographic origin may be an important consideration when planting canyon maple. Few named cultivars exist and certainly much screening and selection work could be done with this species. The only cultivar I know of is Acer grandidentatum 'Schmidt', also called Rocky Mountain Glow maple. This cultivar is under trial at Colorado State University's W.D. Holley Plant Environmental Research Center in Fort Collins, though results have not yet been published. Chris Hartung of the Denver Botanic Gardens also is working on propagation and selection of this species. Canyon maple is available in several nurseries along Utah's Wasatch Front, though it's likely that many people obtain trees by digging small native trees.
As interest in native plant species and low-input, reduced maintenance landscapes grows in the West, trees like canyon maple will get more attention. With its toughness and better adaptability relative to non-native maples, canyon maple has great landscape potential. Using such species, in combination with species that are non-native but well-adapted, will result in more sustainable landscapes. And, instead of our landscapes being second-rate models of those found in the eastern U.S., Asia, or Europe, we will create landscapes with a true western feel.