Picea rubens

Spruces

About 35 species make up the genus Picea – the spruces. Like other members of the family Pinaceae, they are evergreen conifers, related to the hemlocks (Tsuga spp.), firs (Abies spp.) and Douglas firs (Pseudotsuga spp.); however, their closest relatives are the pines (Pinus spp.). Botanists generally agree that the group originated in western North America (the earliest fossilized material from the group was found in Montana), but they currently grow throughout portions of Asia and Europe as well.

Challenging Identifications

Determining that a given tree belongs to the genus Picea is relatively easy. Most spruces have short, sharp, stiff needles that are rarely longer than 1 inch. Each needle attaches singly to the branch via a small, peg-like structure called a pulvinus. These pulvini provide one of the most obvious clues to identify the trees as spruces: They cause the branches of mature trees to feel bumpy.

Spruces typically have scaly bark, and pendulous cones, rather than the upright cones that typify true firs. Additionally, their cones are usually covered in paper-thin scales, rather than the thick scales characteristic of pines and some other conifers. However, like the cones of pines, the base of each scale bears two seeds (although not all scales have seeds – those near the top and bottom of the cone are often sterile).

However, while it is relatively easy to identify a tree as a spruce, it is often challenging to identify the tree to species level. Location provides perhaps the best clues, but it is usually necessary to examine the details of the cones and flowers to identify specimens to species level.

Description and Distribution

Spruces have a conical growth habit, although several cultivars are available that may display a number of different forms, including ground hugging, globular and weeping. Some spruces reach very impressive sizes – a few reach 200 feet in height, but most are between 60 and 120 feet tall.

Spruces are limited to regions with cool climates. Some forms grow in subtropical mountain ranges, but the bulk of the species are at home in the boreal forests of the Northern Hemisphere. In fact, spruces are the dominant forest species throughout much of Asia, Scandinavia and Canada.

Aging Gracefully

Like many other conifers, most spruces have long lifespans; many species are capable of living for at least 800 years. However, some are much older than this — scientists currently consider a 10,000-year-old spruce living in Sweden to be the oldest living tree. However, this particular tree is a clone that sprouted from the original tree in a process called layering; therefore, while the wood of this current tree is not 10,000 years old, the tree (in its various iterations) has lived for this entire time period.

Because of the harsh climate of the location, this particular spruce lived as a shrub for the last several decades or centuries. However, rising global temperatures have recently allowed it to begin taking on a single-trunked, tree-like form.

Commercial Uses

While they may not be quite as commercially important as the pines are, spruces do provide humans with several important resources. One of the most important uses of spruce wood is the manufacturer of paper, as the long fibers of the wood make for exceptionally strong, high-quality paper. The wood is also used in construction, but because it has poor resistance to insects and decay, it is primarily used for interior applications. Spruce wood is also prized for the construction of some musical instruments, especially guitars, violins and other stringed instruments.

Spruce trees also function well as ornamental trees, and a few species are popularly used as Christmas trees. Most firs appreciate cool temperatures, protection from the wind and full sun to partial shade. A few cultivars are known for being drought-resistant, although most require regular irrigation in well-drained soils.