Many different types of evergreens---trees that retain foliage when deciduous ones becomes barren, adding color, beauty and form to the landscape---are naturally found in alpine settings through Northern United States. These trees are naturally adapted to the cold temperatures and poor-quality soil filled with tiny stones and rocks synonymous with alpine settings. Alpine evergreens include hemlock, firs, pines and junipers.
Commonly found pine tree varieties in the alpines of United States include foxtail pine, knobcone pine, whitebark pine, limber pine and bristlecone. Spruces that thrive in alpine settings include Engelmann spruce and Brewer's spruce, while Noble fir, mountain hemlock, California red fir, rocky mountain juniper and subalpine fir are also common in high altitudes.
The majority of alpine evergreens are spread across the western half of North America where most of the significant mountain ranges exist. One of the largest collections of alpine evergreens grows from areas in Central Mexico northward to southern parts of British Columbia. In the West, most of the spruces, pines and firs are native to the Cascade Ranges, Sierra Nevada, the Rocky Mountain states and the mountains of Alaska and Canada. The Carolina Hemlock in the East grows in heights of up to 4,000 feet found in the Blue Ridge chain.
Evergreens found in alpine settings do not grow too large in size due to a combination of factors such as strong winds and poor quality soils. At the highest points, most of these trees that otherwise grow very tall are as big as large shrubs. For instance, foxtail pine that otherwise grows to heights of 50 to 60 feet struggles to grow up to 20 feet tall in mountains. A sheltered spot that is away from strong winds and enriched with good-quality soil encourages whitebark pine to reach 50 to 60 feet tall, but on a mountain it resembles a large shrub with a twisted trunk.
Alpine evergreens are exposed to less-than-ideal conditions that stunt their growth. According to "Trees of America", the whitebark pine takes 200 years to mature in an alpine setting. According to the National Park Service website, documented evidence shows that species of the bristlecone pine have attained ages of over 4,000 years in the White Mountains of California, thus making it the oldest tree species known.
Evergreen conifers are important for the wildlife found at these elevations. For instance, the Clark's nutcracker feeds on the seeds of the whitebark pine and spreads some to other areas, assisting in distribution. Animals such as squirrels and bears thrive on cones that contain seeds. The whitebark pine also deters soil erosion.