Indigenous plants thrive in appropriate zones

By Laura Atwood
Gardens on Spring Creek

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Gardening with native plants offers the opportunity to first get to know natives in their natural habitats and then apply that knowledge to choice and placement of plants within your landscape.

The Federal Native Plant Conservation Committee defines them as "a plant species that occurs naturally in a particular region, state, ecosystem and habitat without direct or indirect actions of humans."

The most important part of this definition is "without direct or indirect actions of humans." For instance, we can trace the origins of cheat grass (Bromus tectorum) to its entry in North America through ship ballast, contaminated seed crop, and one deliberate introduction as a college experiment in Washington. Although you see cheat grass covering expansive areas and, therefore, may think it is a native, because we know it was introduced through the actions of humans, it is not considered a native.

I use plants indigenous to the western United States, specifically Colorado, northern New Mexico and Arizona, and areas of the Great Basin desert, as these are the U.S. natives that perform best in Front Range gardens.

When selecting native plants, I like to learn in which vegetation zone they grow, what habitats they prefer within that zone, and the climatic conditions to which they are adapted. This information helps me to select plants based on the look I am trying to achieve, as well as the specific cultural conditions of my garden.

A vegetation zone "designates a region of more or less uniform climate in which distinctive types of climax vegetation occur" (from "The Naturalist's Guide to the Southern Rockies" by Audrey DeLella Benedict). Along the Front Range there are five vegetation zones: plains (below 6,000 feet), foothills (6,000 to 8,000 feet), montane (8,000 to 9,500 feet), subalpine (9,500 to 11,000 feet) and alpine (above 11,000 feet).

Climate differs within each of these zones but along the plains and the foothills, where most of us live and garden and where many of our garden-worthy native plants grow, the climate is semi-arid (less than 15 inches of precipitation annually), windy, with high solar radiation and low humidity.

Native plants manage to thrive in these conditions with various adaptations. Leaves tend to be small and linear to expose less surface area to the sun, are silvery-gray in color to reflect sunlight, and often have fine hairs or a waxy coating to reduce moisture loss. Wide, shallow root systems grab moisture from our common short, hard bursts of rain, while long taproots draw moisture from deep in the soil during drought.

Some plants are generalists and grow in many vegetation zones, while others are less adaptable and grow in only one or two zones. For instance, Sedum lanceolatum (stonecrop) can be found growing from the plains to the alpine. Liatris punctata (blazing star) confines itself to the plains and foothills.

Besides knowing the vegetation zone in which a plant grows, it is also helpful to know the habitat it prefers. To use our earlier examples, Sedum lanceolatum grows on rocky ground and Liatris punctata prefers dry, open sites. Knowing this information can guide plant placement within your garden – right plant, right place!

I live in the lower montane, surrounded by ponderosa pine and Douglas fir. When selecting plants, I'm mindful of the aesthetic of my surroundings. For instance, although I love cacti and succulents, I use them sparingly as they are not a dominant feature of the landscape. Yes, I have an agave (Agave parryii) and I will be planting a few yuccas this spring, but they are "accessories" to my other plants that grow naturally in the montane zones: Mahonia repens (creeping barberry), Arctostaphylos uva-ursi (bearberry), Juniperus communis (common juniper), Rhus trilobata (skunkbush), Ericameria nauseosus (rabbitbrush), Eriogonum umbellatum (sulphur buckwheat), Liatris punctata (blazing star), and Geum triflorum (prairie smoke).

Of course, if you live on the plains, I'm not suggesting that you only plant a prairie garden. But by considering your surroundings and focusing on plants that complement them and are adapted to the climatic conditions, you'll have a garden that "belongs" and thrives even during summer's heat and drought.

However, if you love the pines and spruces of the montane zone, use them judiciously in your garden and be mindful that they will require additional irrigation during the hot, dry summers of the plains. (The montane zone receives up to 10 inches more of annual precipitation.)

More cultivated varieties of native plants are available to gardeners than ever before. Cultivated varieties offer consistency in mature size and bloom color while native species are sometimes a bit more "free form." Cultivated varieties also allow the urban gardener to select dwarf varieties of large trees, such as pines and spruces, that are better suited to smaller urban lots.

The best way to get know native plants is to get outside – don't forget your field guide – and see them in their preferred habitats.

Laura Atwood is adult programs and special events coordinator at the Gardens on Spring Creek in Fort Collins. The public gardens are located off Centre Avenue about one-half mile south of Prospect Road.