Spruce trees (Picea spp.) are coniferous evergreens. Both the needles and seed cones of spruce trees are attractive to children, but care should be taken when handling spruce branches. Not only is the sap sticky, but the needles can be rough on soft skin. This is especially true of the the Colorado spruce (Picea pungens), which has very stiff, rather sharp needles that can reach lengths of 1 1/4 inches.
Colorado spruce trees have the longest needles of any spruce, according to the Ohio Department of Natural Resources Division of Forestry. Stiff and sharp, these needles mimic the tree's equally stiff, horizontal branches, although some cultivars have a weeping form. The needles range in color from bright blue to grayish-blue or bluish-green. The cylindrical seed cones taper to a point on each end, and can reach lengths of 5 inches. Depending on the cultivar, Colorado spruce trees vary in profile from narrow and columnar to pyramidal with a wide base. They can reach heights of more than 75 feet in the wild, but usually remain at a more manageable height of between 30 and 50 feet in the home landscape.
The Colorado spruce is a cold-hardy tree that is suitable for U.S. Department of Agriculture plant hardiness zones 4 through 7. It thrives in full or partial sunlight, and grows best in moist, organic soil, although it adapts to a wide range of soil types. The Colorado spruce is drought-tolerant and also tolerates growing in areas that collect standing water for brief periods of time.
Selected cultivars of the Colorado spruce are often used in landscaping and as Christmas trees. The long, stiff needles can easily support heavy ornaments, and the striking blue-green color of many of the cultivars adds instant appeal to any landscape. "Glauca" is the most common cultivar, and is often simply referred to as the "Colorado blue spruce." "Montgomery" is a popular variety that features silver-blue needles. "'Thompsenii" not only has bright-blue needles, but the needles are very thick, giving the tree a lush, dense texture.
It is sometimes difficult for the casual observer to tell the difference between a spruce, fir (Abies spp.) and pine tree (Pinus spp.). In fact, the needles are so similar that they are sometimes all referred to as "pine needles," even if the tree is a spruce or fir. This could be because there are more pine species than spruce or fir species. A close look at the needles, however, reveals some key differences. Pine needles grow in bundled clusters of two, three or five. Fir and spruce tree branches bear individual needles. Fir tree needles are flatter than spruce and do not roll easily. If a tree has single needles that roll smoothly between your thumb and forefinger, it likely is a spruce.