BLUE SPRUCE

The 'Blue Spruce' or 'Colorado Spruce' (''Picea pungens'') is a medium-sized evergreen tree growing to 25-30 m (82-98 ft) tall, exceptionally to 46 m (151 ft) tall, and with a trunk diameter of up to 1.5 m (5 ft). It is native to western North America, from southeast Idaho and southwest Wyoming, south through Utah and Colorado to Arizona and New Mexico. It grows at high altitudes from 1800-3000 m (5900-9800 ft) altitude, though unlike Engelmann Spruce in the same area, it does not reach the alpine tree line. It is most commonly found growing along streamsides in mountain valleys, where moisture levels in the soil are greater than the often low rainfall in the area would suggest.

The bark is thin and scaly, flaking off in small circular plates 5-10 cm (1.9-3.9 in) across. The crown is conic in young trees, becoming cylindric in older trees. The shoots are stout, orange-brown, usually glabrous, and with prominent pulvini. The leaves are needle-like, 15-30 mm (0.6-1.2 in) long, stout, rhombic in cross-section, dull gray-green to bright glaucous blue (very variable from tree to tree in wild populations), with several lines of stomata; the tip is viciously sharp.
The cones are pendulous, slender cylindrical, 6-11 cm (2.3-4.3 in) long and 2 cm (0.78 in) broad when closed, opening to 4 cm (1.5 in) broad. They have thin, flexible scales 20-24 (0.78-0.94 in) mm long, with a wavy margin. They are reddish to violet, maturing pale brown 5-7 months after pollination. The seeds are black, 3-4 mm (1.18-1.5 in) long, with a slender, 10-13 mm (0.3-0.5 in) long pale brown wing.
Blue Spruce does not normally hybridize with other spruces, though hybrids with Engelmann Spruce have been found very rarely.

Contents

Uses

Notes

References and external links

Uses

Blue Spruce is one of the most popular garden conifers, grown for its strongly glaucous foliage. Numerous cultivars selected for particularly bright blue foliage have been selected by the horticultural trade, some of them also slow-growing dwarf forms suitable for planting in small gardens. It is also sometimes used as a Christmas tree, though the very sharp needles make it a poor choice for families with children.
Blue Spruce trees are often used by homeowners and landscape architects for home security purposes.^[1] The sharp needles of many species deter unauthorized persons from entering private properties, and may prevent break-ins if planted under windows and near drainpipes. The aesthetic characteristics of the Blue Spruce, in conjunction with its home security qualities, makes it a considerable alternative to artificial fences and walls.^[2]
The National Christmas Tree in Washington, D.C. is a 40-foot (12 m) Blue Spruce planted on the Ellipse in 1978.
Blue Spruce is the State Tree of Colorado (where it is commonly known as Colorado Spruce) and Utah.

Notes

1. Colorado Spruce, an article from homesecurityguru.com
2. Yard Protection: Your First Line of Defense, an article from homesecurityguru.com

References and external links

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★ Gymnosperm Database

★ Flora of North America

★ Arboretum de Villardebelle - photos of cones of ''Picea pungens'' and related spruces

★ Colorado Blue Spruce Seeds (Picea pungens)