The response to drought within regions of the United States has revealed a tendency to reduce the quality of landscaping in the name of water conservation (Hartin et al., 2017; Kuznia, 2015; Reid and Oki, 2013). Given that in many urban areas, landscaping is the de facto environment; it would seem shortsighted to replace live plant materials with artificial turf or other hardscapes. This conversion also risks reducing amenities that society may take for granted. These amenities are clearly illustrated by the reaction of a young Wallace Stegner when he first saw a lawn: “I was nearly 12 before I saw either a bathtub or a water closet; and when I walked past my first lawn, … I stooped down and touched its cool nap in awe and unbelief. I think I held my breath - I had not known that people anywhere lived with such grace” (Stegner, 1948).
Stegner saw his first lawn in Great Falls, MT, after being raised on a homestead with a yard “bare as an alkali flat.” His account illustrates a common experience in the dry interior western and southwestern states where amenity landscaping can offer a welcome respite from often harsh environments. In the last century, the states of Colorado, Idaho, and Utah averaged 18, 24, and 14 inches of annual precipitation, respectively (National Oceanic and Atmospheric Administration, 2015). Preserving the quality of life gained from amenity landscapes in these and surrounding states often requires supplemental irrigation. Unfortunately, a desire to preserve landscapes does not address the very real need to conserve water use in these areas. Water conservation is a complex issue and a successful campaign requires multiple approaches. One approach is the use of drought-tolerant plants. The full spectrum of drought-tolerant landscape plants includes both exotic plants (plants not present before western colonization and adapted to the landscaped environment) and/or native plants [for the purposes of this article, species originating anywhere within the Intermountain West region of the United States that are sufficiently adapted to the intended planting environment as to be sustainable with limited supplemental irrigation (Fig. 1)]. Native plants hold the promise of tolerance to local environments, reduced potential for invasiveness, and the ability to support pollinators and other native wildlife (Dole, 2016). It might also be surmised that such plants can be effectively propagated and produced in their native environment. It is further worth noting that local or regional adaptation is necessary in the Intermountain West where tremendous geographic variation can render a plant native to one region of a state (such as high elevation mountain meadows) ineffective in other regions (such as low elevation urban landscapes).
Native plants have been produced and sold for decades for use in reclamation and other applications (Monsen, 2004). Selection of some native plant species for the landscape industry has also occurred for hundreds of years. A good example is redosier dogwood (Cornus sericea), which has been cultivated since 1656 (Dirr, 1975). Most native plants currently grown for the landscape industry are relatively well adapted to nursery production—and to mesic habitats—making them excellent candidates for planting in traditional irrigated landscapes. With the impetus of water conservation and probable future restrictions, the landscape industry is looking at plants that may be more drought and stress tolerant. But, such plants may also require specific soil conditions, unspecified symbiotic microorganisms, and protection from irrigation-induced diseases (Dumroese et al., 2008; Swiecki and Bernhardt, 2017). In Utah, native plants can be highly uniform [such as the quaking aspen (Populus tremuloides) clone Pando that occupies 106 acres and ≈47,000 stems], or they can be genetically very diverse, as is expressed in sagebrush (Artemisia) species and varieties (DeWoody et al., 2008). Diversity is key to successful wildland reclamation, but is often contrary to the goals of landscape horticulture where uniformity of nursery production and landscape performance is critical to customer satisfaction. To be successful, plant development programs must meet multiple coincidental objectives, such as matching desirable horticultural characteristics with product uniformity. Several different plant development and release program models have arisen in the interior western states to support the selection, production, evaluation, and marketing of native plants.
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