Colorado's Major Tree Species

Colorado's major tree species include bristlecone pine, Colorado blue spruce, Douglas-fir, Engelmann spruce, limber pine, lodgepole pine, narrowleaf cottonwood, quaking aspen, piñon pine, plains cottonwood, ponderosa pine, Rocky Mountain juniper, subalpine fir and white fir.

Characteristics and Descriptions

Bristlecone Pine

Pinus aristata

Bark: Light gray and smooth when young; red-brown with irregular, scaly ridges when mature.

Leaves: Evergreen needles are dark with white lines, they have white pitch dots on both surfaces; to 1-inch long; crowded in a long, dense mass along the twig; generally 5 in a bundle.

Fruit: Cylindrical, dark purple-brown cones; 2 to 3 inches long; 4-sided cone scales with stiff curved points; brown seeds with black mottling and detachable wing.

Elevation: 9,200 to 11,800 feet

Height: 15 to 30 feet

Habitat: On exposed, cold, dry, rocky slopes and high mountain ridges up to timberline; in pure stands or with limber pine.

Relation to Fire: Fires virtually nonexistent in these areas due to low temperatures and a short growing season.


Blue Spruce

Picea pungens

Bark: Gray-brown with thick scales on mature trees.

Leaves: Evergreen needles are blue or light green with white lines; 1 to 1-1/4 inches long with thin, long, flexible and irregularly toothed scales; contains paired, long-winged seeds.

Fruit: Shiny light brown, cylindrical cones; 2 to 4 inches long with thin, long, flexible and irregularly toothed scales; contains paired, long-winged seeds.

Elevation: 6,700 to 11,500 feet.

Height: 70 to 115 feet.

Habitat: Well-drained, sandy soils; moist sites of narrow bottomlands or along mountains streams; often in pure stands.

Relation to Fire: Easily killed by fire due to thin bark, shallow roots and low branches.


Douglas-fir

Pseudotsuga menziesii

Bark: Gray and smooth with resin blisters on young trees; red-brown, very thick and deeply furrowed with broad, often corky ridges at maturity.

Leaves: Evergreen needles are to 1-inch long with bracts at the base.

Fruit: Light brown, short-stalked cones that hang down from the branches; 1-1/3 to 3 inches long; many thin, rounded cone scales on top of long, 3-pointed, winged seeds that stick out beyond scales.

Elevation: 6,000 to 9,500 feet.

Height: 100 to 130 feet.

Habitat: Rocky soils of moist northern slopes; in pure stands and mixed conifer forests.

Relation to Fire: Thin, resinous bark of young trees makes them highly susceptible to fire; after 40 years, trees have developed a very thick layer of bark to protect them during hot ground and surface fires.


Engelmann Spruce

Picea engelmannii

Bark: Gray-brown, thick, with flaky scales.

Leaves: Evergreen needles are deep blue-green with white lines; 5/8 to 1 inch long; slender, sharp and flexible; skunk-like odor when crushed.

Fruit: Light chestnut-colored, oblong cones; 1 to 2 inches long; in upper part of crown with scales that are paper-thin and ragged along the outer edge. Seeds have a single, long and well-developed wing.

Elevation: 8,000 to 11,000 feet.

Height: 45 to 130 feet.

Habitat: High, cold forest environments on moist, northern slopes; with subalpine fir and other conifers.

Relation to Fire: Generally killed by fire due to thin bark, shallow roots, low growing branches, tendency to grow in dense stands and support heavy lichen growth. Large trees may survive low-intensity fires.


Limber Pine

Pinus flexilis

Bark: Light gray, thin and smooth on young trees; at maturity, dark brown, thick and furrowed into scaly ridges. Young branches are very flexible, hence the name.

Leaves: Slender evergreen needles are blue-green with white lines on all surfaces; 2 to 3 inches long, typically 5 in a bundle.

Fruit: Yellow-brown, egg-shaped cones; thick, rounded cone scales that end in a blunt point; seeds are large with a very short wing.

Elevation: 5,000 - 12,000.

Height: 40 to 50 feet.

Habitat: Nutrient-poor soils on dry, rocky slopes; ridges up to timberline and often pure stands.

Relation to Fire: Young trees can be killed by any fire; mature trees can only survive low-intensity fires, but due to the sparse fuels, late snow-melt and short growing season, this species is rarely affected.


Lodgepole Pine

Pinus contorta

Bark: Light brown, thin with many small scales.

Leaves: Evergreen needles are yellow to dark green; 1 to 3 inches long; sharply pointed, stiff, stout, slightly flattened and often twisted; 2 needles per bundle.

Fruit: Shiny, yellow-brown, egg-shaped, serotinous* cones; to 2 inches long with raised, rounded cone scales and a tiny point.

*Seeds released from cones by exposure to extreme heat.

Elevation: 6,000 to 11,000 feet.

Height: 20 to 80 feet.

Habitat: Mostly well-drained soils in high elevations, often in pure stands.

Relation to Fire: Ground fires kill many trees due to thin bark. New stands quickly establish when cones open and seeds are released.


Narrowleaf Cottonwood

Populus angustifolia

Bark: Yellow-green and smooth on young trees; thick, gray-brown and furrowed with interlacing ridges at maturity.

Leaves: Broad-leaf foliage is shiny green with a pale underside; narrow and 2 to 3 inches long; lance shaped with a fine, serrated edge and a pointed tip.

Fruit: Light brown, hairless fruit; inch long; many broad, egg-shaped capsules that mature in the spring, then split into two parts containing many cotton-like seeds.

Elevation: 5,000 to 8,000 feet.

Height: Up to 60 feet.

Habitat: Moist soils along streams; can often be found with willows and alders in coniferous forests.

Relation to Fire: Severe fires can easily kill both young and mature trees. Young trees are able to sprout from roots and/or branches after a fire.


Quaking Aspen

Populus tremuloides

Bark: Green-white, smooth and thin with raised dark patches; on very large trees, trunk base is often gray, thick and furrowed.

Leaves: Broad-leaf foliage is bright green above and dull green below; rounded with a pointed tip, 1 to 3 inches wide on a flattened leaf head; nearly round and sawtoothed.

Fruit: Fruit are catkins; up to 4 inches long; many light green capsules contain 6 to 8 tiny, cotton-like seeds.

Elevation: 6,500 to 11,500 feet.

Height: 35 to 50 feet.

Habitat: Many soil types, especially on well-drained, sandy and gravelly slopes; often in pure stands.

Relation to Fire: Easily killed by fire, but quick to send out many sucker shoots; readily colonizes after a fire.


Piñon Pine

Pinus edulis

Bark: Gray, smooth and thin when young; red-brown, rough and furrowed into scaly ridges at maturity.

Leaves: Evergreen needles are stout and light green; 1 to 1-1/2 inches long; 2 in a bundle.

Fruit: Cones are yellow-brown, unique, short and squatty; 1 to 2 inches long. Each cone contains 10 to 20 large, edible, oily seeds.

Elevation: 5,200 to 9,000 feet.

Height: 20 to 50 feet.

Habitat: Open woodlands; alone or with junipers on dry rocky foothills, mesas and plateaus.

Relation to Fire: Easily killed by fire due to thin bark, relatively flammable foliage and accumulation of dead lower branches.


Plains Cottonwood

Populus deltoides

Bark: Green-yellow and smooth while young; dark gray, thick, rough and deeply furrowed at maturity.

Leaves: Broad-leafed foliage is glossy and yellow-green; 3 to 6 inches long, 4 to 6 inches wide; toothed margins.

Fruit: Inch long with capsules containing 3 to 4 valves; many tiny, cotton-like seeds inside valves.

Elevation: 3,500 to 6,500 feet.

Height: 36 to 190 feet.

Habitat: Found in floodplains, bordering streams, near springs and in moist woodlands; pure stands or with willows.

Relation to Fire: Generally killed by fire; very poor sprouting response.


Ponderosa Pine

Pinus ponderosa

Bark: Dark on young trees; nearly 3 inches thick, red-orange and furrowed into large, flat scaly plates on mature trees.

Leaves: Evergreen needles are stiff, dark yellow-green; 3 to 7 inches long; typically in bundles of 3 that form tufts near the ends of branches.

Fruit: Light red-brown cones; 3 to 4 inches long; egg-shaped with scales that are tipped by a sharp point; small, long-winged seeds.

Elevation: 6,300 to 9,500 feet.

Height: 40 to 160 feet.

Habitat: Dry, nutrient poor soils in open park-like stands or with Douglas-fir, Rocky Mountain juniper and spruce.

Relation to Fire: Resistant to fire, due to open crowns, thick, insulating bark, self-pruning branches, high moisture content in the leaves and thick bud scales.


Rocky Mountain Juniper

Juniperus scopulorum

Bark: Gray-brown, thin, fibrous; shreds with a red-brown color underneath.

Leaves: Evergreen scalelike needles are small, gray-green or silvery.

Fruit: Blue-gray berries; waxy and juicy; inch in diameter; typically two-seeded.

Elevation: 5,000 to 9,000 feet.

Height: 20 to 50 feet.

Habitat: Grows on rocky soils in the foothills and on the plains; often associated with piñon pines.

Relation to Fire: The resinous wood is very flammable. Low intensity fires easily kill this tree due to its thin bark and compact crown.


Subalpine Fir

Abies lasiocarpa

Bark: Gray and smooth with resin blisters while young; shallow fissures and scaly when mature.

Leaves: Evergreen needles are dark, blue-green with silvery lines on both surfaces; 1 to 1-1/2 inches long; flat and blunt tipped; crowded and curved upward on twigs at nearly right angles.

Fruit: Upright, cylindrical, very dark purple, 2 to 4 inches long in the upper part of the crown; fine, hairy, cone scales; long, broad-winged seeds. These deciduous cones fall apart when mature so they are rarely found on the ground.

Elevation: 8,000 to 12,000 feet.

Height: 60 to 100 feet.

Habitat: Cold, high elevation forests; with Engelmann spruce and other conifers.

Relation to Fire: Generally killed by low-intensity fires because of thin, flammable bark, shallow roots, low-growing branches and dense growing conditions. Seeds readily germinate on recently burned ground.


White Fir

Abies concolor

Bark: Light gray and smooth with resin blisters on young trees; deeply furrowed into corky ridges and orange cracks when mature.

Leaves: Evergreen needles are light blue-green or silvery with white lines on both surfaces; 1 to 3 inches long; flat and rounded.

Fruit: Oblong, olive-green to blue cones; 3 to 5 inches long; upright on topmost twigs; fine, hairy cone scales; paired, long-winged seeds.

Elevation: 7,900 to 10,200 feet.

Height: 60 to 125 feet.

Habitat: Moist soils of high mountain valleys; in pure stands and with other firs.

Relation to Fire: Young are usually killed by low-intensity fires due to thin, resin blistered bark and drooping lower branches; mature trees are moderately fire tolerant.