Picea pungens, first described in 1879 by Georg Engelmann (1809–1884) is commonly known as Blue spruce, Colorado Blue spruce, White spruce, Silver spruce, or Parry spruce; as épinette bleue in French Canadian and as pino real in Spanish. It is the state tree of Colorado.
Description. Colorado spruce is an evergreen coniferous species of tree which will grow to mature heights of 165 feet (50 m) tall with a trunk 5 feet (150 cm) in diameter at breast height.
- Crown is broadly conic in shape.
- Bark is gray-brown in color.
- Branches grow slightly to strongly drooping; non-pendant twigs are stout and yellow-brown in color, usually glabrous.
- Buds are dark orange-brown, 0.24 to 0.48 inch (6 – 12 mm) in size, the apex rounded to acute.
- Foliage is needle-like, 0.6 to 1.2 inches (1.6 – 3 cm) long, 4-angled in cross section, rigid, blue-green in color, bearing stomata on all surfaces, with a spine-tipped apex.
- Pollen cones are red in color, growing in whorls of 3 to 5 at the proximal end of new shoots, primarily borne in upper crown.
- Seed cones are also borne in the tree’s upper crown. They are pale green or red when fresh, ripening to pale buff brown, 2 to 5 inches (5 -12 cm) long with elliptic to diamond-shaped scales, widest below middle. Seed cones mature in August; seed shed is from September into winter.
Distribution. This species is native to USA — the states of Idaho, Wyoming, Utah, Colorado, New Mexico and Arizona, growing in the montane zone at elevations varying from 5800 to 8800 feet (1830 – 2740 m) above sea level in the northern range of the species, and to 6800 to 9800 feet (2130 – 3050 m) in southern areas. It prefers areas where the climate is cool and summer-wet, with mean winter minimum temperatures of 12° to 48°F (-11.1° – 8.9°C) and mean summer maximum temperatures of 70° to 72° F (21.1° – 22.2°C). Average annual precipitation varies from 18 to 24 inches (460 – 610 mm), with half of the annual precipitation falling during the growing season. It is the most drought-tolerant species of Picea in North America. It is hardy to USDA Zone 3 (cold hardiness limit between -40° to -30° (-39.9° to -34.4°C).