Woody Plant Trials on Colorado’s Western Slope

By James E. Klett, Ph.D. Professor & Landscape Horticultural Specialist Colorado State University

As part of our multi-site woody plant trials throughout Colorado, one site is at Orchard Mesa Research Station, now called Colorado State University – West Campus. This site has had woody plant coalition trials for 19 years, and the climatic and soil conditions are quite different from sites along the Front Range of Colorado. This research has been sponsored for years by the Colorado Research and Education Foundation (CHREF) and Plant Select®.

In this short article, I would like to talk about some real winners from this trial site, which have been growing for close to 20 years. Many have also proven to be winners at our other research sites on the Front Range. The following are seven woody plants that have performed well in western Colorado and should be planted more not only in landscapes in that area, but also in many other locations in the state and beyond, adding diversity to our woody plant canopy.

Acer tataricum, ‘GarAnn’ pp 15023 (2007 Plant Select®) – Hot Wings® Tatarian Maple

This smaller maple can be grown single stem or multi-stem, maturing to about 18 to 20 feet in height and 15 to 20 feet in width. It will grow in clay, loam or sandy soil with higher soil pH. The brilliant red samaras look like flaming flowers throughout the summer. It is a very attractive tree with more showy orange-red fall colors. It is cold hardy to zone 4.

Cotoneaster racemiflorus soongoricus (2017 Plant Select®) – Sungari Cotoneaster

This shrub matures to about 6 to 9 feet in height and width, prefers sun, and has a low-water requirement. The small white flowers blanket this broad, rounded shrub during late spring. It then produces showy red fruit in late summer along with some nice orange-red fall colors. It is quite cold hardy to zone 4 and up to 7,000 feet elevation.

Cupressus arizonica ‘Fandango’ – Fandango Cypress

This evergreen has a more upright to pyramidal growth habit with more blue in its overlapping, scale-like foliage. It prefers sun and adapts to dryer, well-drained, more clay-like soils. It can grow 20 to 25 feet tall and 10 to 15 feet wide. It is hardy to zones 4 or 5 and up to 6,000 feet or more.

Juniperus scopulorum ‘Woodard’ – Woodward Columnar Rocky Mountain Juniper

This easy-care Rocky Mountain native evergreen has soft-textured, dark green foliage, which turns grey-blue in winter. It grows 15 to 20 feet tall and only 2 to 4 feet wide. It has a single leader with short side branches allowing the plant to retain its narrow upright shape without spreading outward from wind or snow loads. It is a very low-water plant and hardy to zones 3 or 4 and up to 8,500 feet in elevation.

Quercus muhlenbergii – Chinkapin Oak

This oak is proving itself adaptable both in western Colorado and along the Front Range. It can mature to about 35 to 50 feet in height and width, and is hardy to zones 4 or 5 and up to 6,500 feet in elevation. The sharply toothed leaves are dull green above, with a pale silvery lower surface. Fall color can vary from yellow to red to brown. It requires low water and is quite adaptable to our various soil types.

Sorbus hybrid – Oakleaf Mountain Ash

This more medium-size tree matures to about 25 to 35 feet tall with a spread of up to 15 to 20 feet, and will grow well in sun to filtered shade. The leaves are deep green, lobed and resemble those of an oak. Clusters of white flowers are produced in spring, leading to deep red fruits in summer and fall. It has a more upright to oval growth habit as it matures. It is cold hardy to zones 4 or 5 and about 6,000 feet in elevation.

Xanthoceras sorbifolium – Yellowhorn – Popcorn Shrub

Generally grown as a larger multi-stem shrub with attractive flowers that are white with yellow centers, which resemble popcorn and eventually turn red in late spring to summer. It grows about 15 to 25 feet tall and about 15 to 25 feet wide. It is tolerant of our more alkaline soils and moderate drought. The leaves are a dull dark green and resemble that of a mountain ash. It is hardy to zone 5 and prefers full sun.