Gardening in high deserts and mountains of the Southwest presents some unique challenges because the growing season is short with cool nights, hot days and plenty of wind. In Northern Arizona, Northern and South-Central mountains of New Mexico, and most areas of Colorado and Utah, elevation plays a role in selecting the best plants for a landscape. Plants native to high-altitude conditions usually survive better in a landscape than do plants you might love but simply have trouble growing in extreme climates. Native plants also can support local wildlife and often use less water than non-natives.
Plant breeders like to make Southwest gardening more fun and successful for all of us by breeding the best qualities of our native plants with other characteristics – such as more or larger flowers – to give us plenty of choice in our gardens. Here are some of the best native and native hybrids for higher elevation Southwest gardens.
Growing trees native to the Southwest mountains, and even to your specific state’s mountains, helps you find success, uses less water, and helps native wildlife. The Gambel Oak (Quercus gambelii) grows at elevations of 4,500 to 8,500 feet. In full sun and with little water, the member of the Beech family can grow to nearly 30 feet high and 20 feet across. It grows faster if watered deeply on a regular basis, but can handle dry spells. Its leaves turn from dark green in summer to a copper/bronze in fall before dropping. This is a good choice for a shade tree to cool a home or patio in summer but let some sun through in winter. Also called Scrub Oak, the Gambel is native to mountains of New Mexico and Colorado.
The Quaking Aspen (Populus tremuloides) is a favorite mountain tree thriving at up to 10,000 feet, but it needs more water than many natives, especially if grown at lower altitudes (about 4,000 to 5,500 feet). The Valley Cottonwood (Populus deltoides) is tall with one of the most attractive canopies, favoring river valleys but with roots that can invade sewer and water lines. A few shorter trees can grow like tall shrubs or multitrunked trees. An example is New Mexico Olive (Foresteria pubescens) with twisting branches. The Rocky Mountain Maple (Acer glabrum) grows more like a tree, but also is considered a tall native shrub.
Native shrubs also provide shelter or food for native insects and wildlife. As urbanization spreads, adding native shrubs into local landscapes can help provide habitat for birds, butterflies and mammals. The Serviceberry (Amelanchier alnifolia) grows at altitudes of 5,000 to 10,000 feet and provides color in spring when it flowers, green in summer, blue-black fruit for wildlife, and orange-red leaves in fall. The shrub grows to nearly 12 feet high, depending on the cultivar. They have low to moderate watering requirements.
Snowberry (Symphoricarpos albus) and Buffaloberry (Shepherdia canadensis) also grow in foothills or mountains of about 5,000 to 8,500 feet for serviceberry and 11,500 feet for buffaloberry, and provide berries for birds and small mammals.
Although native to plains, Agastache (A. foeniculum) grows well in Southwest intermountain gardens. The plant, often called hyssop, anise hyssop, or hummingbird mint, is a perennial member of the mint family. It is not prone to disease and is cold hardy down to zone 4 and summer hardy to zone 8 (with a few taking the heat of zone 9). Hyssops are attractive to hummingbirds, but not to deer, so they are big-plus perennials in high altitude gardens.
Although truly native hyssops feature mostly mint-like leaves and purple flowers, hybridizers have cultivated various colors and needle-like leaves. Most hyssop leaves are fragrant, and the plants bloom in late summer to early fall. They love full sun, but need a little afternoon shade in warmer climates of the Southwest. This might affect flowering, but not enough for anyone to avoid this versatile perennial.
Other members of the mint family, such as Nepeta (catmint) and Cuban oregano often do well in high-altitude gardens. Just beware that some mint relatives, such as horehound, can become invasive. Additional perennials for the high-altitude Southwest garden are sages, either culinary or salvia species.
You’ve no doubt seen us tout many penstemon varieties for hot Southwest gardens. Scarlet penstemon is a pretty native of Texas Hill Country and similar to a wild one that just appeared in my yard. Others are native to cooler or higher regions, like Rocky Mountain penstemon. My favorite is pineleaf penstemon (P. pinifolius), also called Pineleaf Beardtongue. Bees and hummingbirds love the trumpet-shaped flowers of penstemons, which grow best in full sun or in morning sun with some afternoon shade.
Pineleaf penstemon requires a little more water than some to maintain its lush carpet of orange flowers above pine-like leaves. It begins blooming in late spring and needs little care, just shearing of spent flower stalks in early spring. Give it soil that drains well. One reason it is such a great groundcover is its propensity to spread. The plant becomes larger, but it also makes baby plants nearby. We have dug them up and transplanted them with good success. High Country Gardens sells tall and compact pineleaf penstemons, one with a redder flower.
Feather Reed Grass (specifically Calamagrostis arundinacea ‘Karl Foerster’) is a hardy and beautiful ornamental grass for high-elevation gardens of the Southwest. It grows pretty green blades that add flower stems in summer that can rise nearly two feet above the blades. The wheat-like stems are favorites of birds and look elegant but natural blowing in the breeze, even through winter.
In higher elevations of 7,500 feet or more, the plant does best when planted in spring. Warmer climates can plant feather reed grass in fall, just being sure to give its roots time to grow before the first frost hits. It needs a little more deep water than some native grasses to grow and develop a flush of flower stalks. Other than that, care is easy. Just cut the entire leaf base close to the ground in early spring and it will regrow.
Some plants are not native to your state or altitude but have adapted to the climate or have qualities that make them good choices. You don’t have to plant only natives; find other plants that grow well in your state and at your altitude to complement native plants by mixing up color, bloom time, height or texture. And don’t be afraid to try native hybrids; they should work as well as native plants you see growing naturally nearby.
Teresa Odle is the editor of African Violet Magazine, a freelance editor for BobVila.com, and author of a blog on low-water gardening in the Southwest. Teresa trained as a Master Gardener in Albuquerque, N.M. She grew up in the Phoenix area, and has lived in the mountains of northern New Mexico. Teresa and her husband now attempt to manage four acres of land in zone 6B of southeastern New Mexico. The land includes a large xeric garden, herbs and vegetables, and a small orchard that borders the Rio Ruidoso in Lincoln County. Teresa’s blog, Gardening in a Drought, won a 2016 national award for best writing in digital media from the Association for Garden Communicators.