The “Life Zones” of Colorado
The US Department of Agriculture publishes a list of Plant Hardiness Zones to help gardeners determine which plants are likely to survive in a given geographical location. But these zones are based on average minimum winter temperatures and don’t take other factors like precipitation and soil condition into account. Most of Metro Denver falls in USDA Zones 4-6, but with the wide range of growing conditions facing Coloradans, knowing a climate zone may not be enough information for successful planting.
To improve growing success for Colorado landscapers and gardeners, Colorado State University has developed six zones that take diverse growing conditions into account based on the native plants that thrive in those locations. They call these areas the Life Zones of Colorado. Here they are in order of increasing elevation.
The Plains Life Zone
Located in eastern Colorado, it’s where most of the state’s population resides. The Plains zone ranges from 3,500 to 5,500 feet and is dominated by native grasslands and streamside cottonwoods.
The Foothills Life Zone
Ranging from 5,500 to 8,000 feet, the Foothills Life Zone is dominated by dry land shrubs such as Gambel oak and mountain-mahogany. In southern and western foothills, piñon and juniper woodlands and sagebrush are also native.
The Upper Sonoran Life Zone
This zone is located in western Colorado at altitudes below 7,000 feet and in the San Luis Valley below 8,000 feet. This zone is characterized by semi-desert shrublands with piñon pine and juniper woodlands in its upper reaches.
The Montane Life Zone
This zone, at elevations of 8,000 to 9,500 feet, is where you find Colorado natives ponderosa pine, Douglas-fir, lodgepole pine, and aspen growing in thick forests.
The Subalpine Life Zone
At 9,500 to 11,500 feet dense forests of subalpine fir and Engelmann spruce are the dominant native trees of the Subalpine zone.
The Alpine Life Zone
Above timberline at 11,500 feet and hugher, this zone is made up of hardy native grasslands called tundra.
Zones Are Only Starting Points
Just as with USDA Zones, Colorado Life Zones are general guides to where plants are most likely to survive. Other factors like exposure to sun and wind, locally different soils, and supplemental irrigation can affect a plant’s tolerance to its environment, especially in urban microclimates.
In many landscapes plants native to higher, wetter locations can be planted successfully at lower altitudes with supplemental irrigation, and lowland plants can succeed with protection from the harsh elements of higher elevations.
Questions? Call a Pro
Professional arborists know the trees and shrubs that will thrive in your landscape, staying strong, healthy and beautiful. And they have the right skills and tools to plant them successfully.
Donovan Arborists offers planting, pruning, and shearing services as well as a complete landscape maintenance package for property in the Denver area. And we’re always happy to give free estimates to homeowners and property managers for any services they may need.