Blue Spruce: State Tree of Colorado and Utah

The State tree of Colorado and Utah is the Colorado Blue Spruce (Picea pungens). This conifer is also known as blue spruce, Colorado spruce, silver spruce and pino real. The blue spruce is native to the Rocky Mountains and like cool moist climates. It is hardy to -40º and is not susceptible to frost damage. The cold temperature tolerance of the blue spruce, along with its unique blue-gray coloration and overall uniform conical shape, make it a popular specimen tree in the landscape in northern climates. It does well in sun or shade situations. The conifer is also somewhat drought and flood tolerant.

The blue spruce is a slow growing tree. The height tends to be 30-60 feet, but older trees exist that reach 120 feet. The lower branches often touch the ground, and the branch width at the base can be 10-20 feet across.

The dense needle growth makes this conifer a good choice for a shade tree. Blue spruce can be planted in mass groupings, or as part of a tree collections. Cultivars include 'Fat Albert', 'Glauca Pendula', 'Hoopsii', 'Iseli Fastigiata', 'Foxtail', 'Koster', 'Moerheim', 'Montgomery', 'Pendula', and 'Thompsenii".

Blue spruce is monoecious meaning it has both male and female cones. It is not grown for lumber as the wood is weak and full of knots. Trees are grown for Christmas trees. They are sought after because the still branches mean the tree will hold its shape after cutting.

This conifer provides shelter for birds and for foraging animals when planted in the wild. In some areas of its natural growth, the blue spruce is the nesting ground of several endangered and protected birds such as northern goshawks, bald eagles, and flammulated owls.

Blue spruce can be propagated by seed or by grafting soft wood cuttings to understock. Understock refers to trees that are grown specifically to be the host root system for the grafted cutting. A cut is made on the understock and the wood cutting is inserted. The wound is wrapped and a tenting material may be used to prevent the grafting from rapid fluctuations in temperature and humidity.

Blue spruce had several predators. Insect damage can be caused by spruce seed moth, cone cochylid, coneworm, budworm, needle miner, and aphids. Insect damage tends to be minimal. There can be some damage for diseases such as rust, root rot, and snow mold. Cankers and tip blight are usually not fatal but do detract from the tree's general appearance

Sources
Picea pungens, National Forest Service, http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/picea/pungens.htm
Picea pungens, University of Connecticut, http://www.hort.uconn.edu/plants/p/picpun/picpun1.html
Picea pungens, USDA Forest Service, http://www.fs.fed.us/database/feis/plants/tree/picpun/all.html
Grafting and Seed Collecting Tips for Conifers, by Dax Herbst, http://home.att.net/~Conifers/Graftingtips.htm
Picea pungens, Ohio State University, http://www.hcs.ohio-state.edu/hcs/TMI/Plantlist/pi_ngens.html