While many gardeners may be familiar with the more prostrate forms of juniper shrubs, the fact is most species of junipers grow as trees in the wild. Juniper trees (Juniperus spp.) are nonflowering plants that reproduce by producing cones, therefore appropriately called gymnosperms. In North America, juniper trees are often given the vernacular name of "cedar," even though they are not closely related to true cedar trees (belonging to the genus Cedrus).
Juniper trees are native to dry forests and hillsides across much of the Northern Hemisphere. One species does naturally occur in eastern Africa, according to Flora of North America Online. In fact, there are over 10 species native to North America, and over 20 species native to China (10 of which are only found in China).
Overall there are about 60 species of plants in the genus Juniperus, but not all develop into trees. Example of juniper tree species include: West Indian cedar (Juniperus barbadensis), Bermuda cedar (Juniperus bermudiana), Chinese juniper (Juniperus chinensis), eastern red cedar (Juniperus virginiana), western juniper (Juniperus occidentalis), alligator juniper (Juniperus deppeana), Himalayan weeping juniper (Juniperus recurva), Rocky Mountain juniper (Juniperus scopulorum) and single-seed juniper (Juniperus squamata). Horticulturists have selected seedlings or branch mutations of trees and given them variety (cultivar) names for use in gardens because of their more ornate foliage or attractive growth forms or mature sizes.
The spiky, short-needled leaves of juniper trees are evergreen and range in color from dark green to shades of medium to blue-green or grayish green. Crush the juniper's foliage or twigs and a pleasant aroma is emitted. The needles are arrange in an alternate arrangement on branch twig tips, sometimes in four ranks or in whorled clusters of three, according to Flora of North American Online. The bark of juniper trees is often masked by the foliage, but it is generally thin and flakes away in attractive strips. The bark's color varies among species but is usually red-brown to grayish dark brown. Male and female cones occur on separate trees, with female trees producing small cones on branch tips that take one to two years to mature and release seeds.
Juniper trees can attain a wide, spreading canopy or become rather tall, upright trees. Species that are rather wide-spreading include needle juniper (Juniperus rigida), common juniper (Juniperus communis) and Ashe juniper (Juniperus ashei), all of which can grow 20- to 25-feet tall and 20-feet wide. Taller, upright, but narrower juniper trees include Chinese juniper, which grows 70-feet tall and 20-feet wide. Alligator juniper reaches 70-feet tall and 12-feet wide; western juniper, 40-feet tall and 5- to-10 feet wide; and Rocky Mountain juniper, 50-feet tall and 20-feet wide. Larger, more classic-looking trees include the eastern red cedar, which will grow 50- to 100-feet tall and 15- to 30-feet wide and the West Indian cedar, which becomes 65-feet tall and 50-feet wide.
Since juniper trees are well-adapted to dry soils, wind and climates that are both hot in summer and cold in winter, they are often used as garden and landscape plants. Their evergreen boughs block winds, screen unpleasant views and hold the soil on hillsides. The fragrant wood also is used as lumber to make furniture or buildings, or to create wood paneling or firewood. Pyramid-shaped juniper trees can be cut and used for Christmas trees, or their boughs can be shaved and used for garlands and wreaths.