Remember: the same vegetation zone will occur at a higher elevation to the
south, and a lower elevation to the north, and will change with the aspect
(direction it faces) of the hillside, terrain, and surface or groundwater
availability. Regard the following elevations as approximate! –Jeanne Willson
From the Colorado Native Plant Society website (with some edits):
Vegetation Zones:
Alpine: Above 11,500 feet (tree line). Characterized by tundra: land of thin soil,
rocks, a very short growing season, and frost any day of the year. Annually 30-55
inches of moisture, most from snow (200 to 400 inches per winter). Magnificent carpets
of dwarfed flowering plants in June, July, and August.
Subalpine: From 10,000 to 11,500 feet. Characterized by thick spruce/fir forests.
Aspens grow at lower elevations in this zone. Annually about 25-40 inches of moisture,
most from snow (about 250-350 inches). Lush wildflower growth mid-June through
August.
Montane: From 8,000 to 10,000 feet. Open Aspen forests, sometimes with heavy
undergrowth of shrubs (snowberry, currants, elderberry). Colorado blue spruce in
moist areas. At lower elevations some large stands of Ponderosa Pine with scattered
Douglas fir on north facing slopes. Annually about 18-30 inches of moisture, 1/2 to 3/4
from snow. Moderate to lush wildflower growth from June-August.
Foothills (including Mesas): From 6,500 to 8,000 feet. Pinyon pine, juniper, and
oak forests, often quite thick. Pockets of Douglas firs. Ponderosa pines at higher
elevations and latitudes. Numerous shrubs: serviceberry, mountain mahogany,
snowberry. Annually about 14-25 inches of moisture, about half from snow. Moderate
to very good wildflower growth in May and June, highly dependent on winter and spring
rains.
Plains: From 3,500 to about 6,500 feet covering the eastern third of Colorado. The
plains are, where undisturbed by agriculture, a mixed grass prairie. Sandy hills may
have shrubs such as sagebrush and rabbitbrush mixed with cacti and yucca.
Cottonwoods, willows, and boxelder are found along streams. Percentage of days with
sunshine is very high and humidity is quite low. Annual precipitation is less than 20
inches with about a quarter of that from snow. Wildflowers in undisturbed areas can be
very good from March through June.
Desert and Semi-desert (including Canyons): Typically from 4,000 to 6,500 feet.
Arid. Annually 5-14 inches of moisture, 1/4 or less from snow. Desert and semi-desert
areas are characterized by open, sandy, gravelly flats with scattered shrubs (saltbush,
sagebrush) and boxelder or cottonwoods along washes. Higher semi-desert canyons
have pinyon pine, juniper, and oak with some thick patches of yucca, sagebrush,
mountain mahogany, and other shrubs. Wildflower growth is best from March to June
but is highly dependent on winter moisture.
Habitats:
Some plants bloom only in special, very limited habitats; others tolerate a variety of
growing conditions. The following thirteen categories describe the habitats of Colorado:
Tundra: Land above tree line characterized by a short growing season, intense sun
and wind, thin soils, very high snow fall and high rain fall, and low growing sedges,
grasses, dwarf shrubs, and herbs.
Scree: Fields (often extensive) of small, loose, slab rock. Common below tree line and
very common above tree line. Pockets of endemic (=found only there) wildflowers
where soils accumulate.
Woodlands: Areas forested with Spruce, Fir, Pine, Aspen, Oak, Juniper, Douglas Fir.
Wetlands: Wet meadows, fens, seeps, etc.
Streamsides: Moist areas along streams.
Openings: Small to large clearings in various vegetation zones. The openings are
caused by soil conditions, fire, avalanches, wild animals, or humans.
Meadows: Grass, shrub, and wildflower-filled large open areas with few, if any, trees.
Rocks: Areas of large rock in canyons or mountains.
Canyons: Deep and long depressions with walls of cliffs and slopes. Pinyon pine,
juniper, and sagebrush are common.
Shrublands/Grasslands: Arid lands characterized by shrubs, grasses, and a lack of
trees.
Prairies: Low elevation, gently rising and falling lands of grasses, wildflowers, and few
trees.
Disturbed areas: Roadsides, mined areas, timbered lands.
Semi-deserts: Shrublands, grasslands, Pinyon-Juniper woodlands, or sand and gravel
relatively barren lands.