The spruce tree, genus Picea, is a common evergreen tree that grows in northern climates. Native to the North American continent, there are 35 different types of spruce trees around the world. These trees prefer the cool, seasonal climates and acidic soils of the earth's boreal forests and temperate biomes, although some rare spruce trees have adapted to the warmer regions in northwest Mexico and central Japan regions. The scientific names for individual spruce trees are associated with their Latinized genus name, Picea, and the species name in Greek. For example, Picea likiangensis is the scientific name for the Likiang spruce that grows in southwest China.
Most spruce trees are so named for the region in which they grow. Picea abies, or Norway spruce, grows abundantly in northern Europe. The Picea ocovata, or Siberian spruce, endures one of the harshest climates in the world, in the northern fringes of Siberia. The blue spruce, commonly called the Colorado spruce, or Picea pungens, populates the densely forested regions of the Rocky Mountains in North America. Spruce trees grow all over the world, including Taiwan, Burma, Canada, Korea, Serbia, in the Himalayas, and in the Caucasus Mountains of Turkey.
Despite the wide variety of species, all the different types of spruce trees have several characteristics in common. They are all gymnosperms, reproducing through the formation and development of spruce seeds within cones. All produce short, stiff needles within a compact pyramidal or conical form. All types of spruce prefer full sun, cool temperatures and moist soil. They will grow in heavy clay soil but cannot tolerate arid climates or heavy pollution.
Gardeners appreciate the easy care and low maintenance of spruce trees. Planting spruce requires little soil preparation, but the trees do require a large space in which to grow. Most trees reach heights of 60 feet (18 m), although some types of spruce may reach only half that height. Dwarf varieties are best for the small garden. Caring for all types of spruce trees is easy, requiring little more than occasional pruning and watering during dry seasons.
Spruce trees are planted for their pleasant pyramidal shape and longevity. Planted in rows or groups, the trees provide an excellent wind break from cold north winds. Their yearlong color lends a visual appeal from winter's gray and gloomy environment. Researchers from Sweden discovered an ancient Norway spruce tree estimated to be over 9,000 years old. The slow-growing spruce sports an attractive symmetrical, conical habit and is a popular choice for Christmas trees.