Rocky Mountain Maple

Rocky Mountain maple (*Acer glabrum*) is a western North American native that grows as a small tree or upright, often multi-stemmed shrub. Red young shoots, fragrant yellow-green late-spring flowers, summer samaras, and fall foliage ranging from yellow to red create several seasons of interest. Size and performance vary with subspecies, seed source, and climate, so locally adapted nursery stock is useful. ## Form and landscape use This maple can be grown as a large shrub or trained to a small single- or multi-trunk tree. University sources describe a typical range of about 15–30 feet tall and roughly half as wide, while one arboretum specimen is listed at 10–20 feet; the catalog’s 25-by-15-foot estimate fits within those references. Its rounded crown and flexible size suit a native border, woodland edge, or smaller landscape where a tree with seasonal color is wanted. Propagation is difficult, so it may be less available than common landscape maples. ## Site and seasonal performance Utah State’s arboretum lists it for USDA Zones 4–7, with moderate growth and water use. It tolerates full sun to shade, but naturally favors cool mountain sites and protected locations; hot exposures can cause leaf scorch. Choose well-drained soil, ideally deep loam. It tolerates acidic through moderately alkaline soils, dry conditions, and strong winds, though sunny plantings may still need periodic supplemental irrigation after establishment. Small yellow-green flowers appear after the leaves in late spring; winged samaras develop in summer and can remain into fall. Green, deeply lobed leaves turn yellow, orange, or red in autumn. See [USU’s Botanical Center profile](https://extension.usu.edu/botanicalcenter/trees-of-varga-arboretum/rocky-mountain-maple), its [Western Native Plants guide](https://cwelwnp.usu.edu/westernnativeplants/plantlist_view.php?id=102&name=acerglabrum), and [Oregon State’s species account](https://landscapeplants.oregonstate.edu/plants/acer-glabrum). ## Maintenance Low maintenance when the planting site matches its cool-climate preferences. Water through establishment and during extended dry weather, especially in full sun. Keep the root zone well drained. Remove dead or damaged stems and prune only as needed to maintain the chosen single- or multi-stem form; retain the natural rounded outline rather than shearing it into a hedge.