Picea engelmannii, with common names Engelmann spruce, white spruce, mountain spruce, or silver spruce, is a species of spruce native to western North America, from central British Columbia and southwest Alberta, southwest to northern California and southeast to Arizona and New Mexico; there are also two isolated populations in northern Mexico. It is mostly a high altitude mountain tree, growing at 900 metres (3,000 ft) β 3,650 metres (11,980 ft) altitude, rarely lower in the northwest of the range; in many areas it reaches the alpine tree line.
The cones are longer than most other North American spruces, pendulous, cylindrical, 8β15 cm long and 2 cm broad when closed, opening to 3β4 cm broad. They have smoothly rounded, thin, flexible scales 2 cm long. The immature cones are dark purple, maturing red-brown 5β7 months after pollination. The seeds are black, 3β4 mm long, with a slender, 12β18 mm long pale brown wing.
Picea breweriana grows very slowly, typically less than 20 cm (8 in) per year. It occurs mainly on ridgetop sites with very heavy winter snow to provide a steady source of meltwater through the spring, but dry in the summer. The harsh ridgetop conditions minimize competition from other much faster-growing trees like Douglas-fir. It is very well adapted to cope with heavy snow and ice loads, with tough branches, and the drooping branchlets shedding snow readily.