The genus Juniperus contains between 50 and 68 different species, depending on the authority consulted.
Juniper trees inhabit much of the world’s land area, including parts of North America, Europe, Asia and Africa. Junipers are common plants and trees across arid regions of the American southwest; in many places, they are the primary tree species present.
Most individual species have fairly restricted ranges, but one species – the common juniper (Juniperus communis) – is the world’s most widely ranging conifer. It is the only member of the genus to live in both Europe and North America.
Description and Form
Junipers have awl- or scale-like leaves; some species possess only one type of leaf, while others bear both types. For example, common junipers possess only the awl-like leaves, while Chinese junipers (Juniperus chinensis) produce both awl-like and scale-like leaves. The leaves are typically dark green in color.
Like many other members of the family Cuppressaceae, some junipers live very long lives. Some Rocky Mountain junipers (Juniperus scopulorum) are known to have lived for over 2,000 years. The trees produce very narrow growth rings, which makes them a coveted timber species.
California’s own juniper species – the California juniper (Juniperus californica) – lives primarily within the state’s borders. Usually growing as a shrub, the plant also grows as a short tree, reaching about 25 feet in height.
Odd, But Useful Cones
Junipers have odd cones, whose scales grow together around the seeds. They look like, and are often mistaken for, berries. Inside the blue (rarely orange) flesh, the cones hold up to a dozen tiny seeds. They rely heavily on the seed dispersal activities of birds, which leads them to grow in places under which birds congregate, such as fencerows and under utility lines.
Humans use the cones in a variety of culinary applications. Perhaps best known as the primary flavoring agent in gin, juniper berries are also used in spices, sauces and to flavor some beers. The very word “gin” is a corruption of the word “genever” – the Dutch word for juniper. Primitive cultures have used the berries for a variety of medicinal purposes (to varying degrees of efficacy), such as inducing labor or miscarriage, treating diabetes and relieving the symptoms of asthma.
Use and Cultivation
Juniper wood is extremely resistant to decay and insects, which make is very useful for outdoor construction. Humans use junipers extensively for ornamental plantings, and because they often tolerate arid conditions and are unpalatable to many foraging animals, they are helpful for soil stabilization projects. Numerous cultivars have been produced, some of which grow as sprawling ground covers while others form upright, single-trunked trees.
Junipers typically adapt well to a variety of different well-drained soils, but most require full sun exposure or light shade to grow. However, they form coarse root systems, which make them very difficult to transplant, except while they remain young. Many junipers — especially the improperly named red cedar (Juniperus virginiana) — produce very dense foliage, which makes them useful for windscreens or providing privacy. Although they are not common street trees, their hardy nature, ability to adapt to varying soil conditions, strong wood and lack of maintenance problems make them excellent candidates in some areas.
Despite their many positive traits, some Junipers are susceptible to a variety of pest and pathogens. For example, bark beetles, aphids and mites frequently feast on the trees, cedar-apple rust and various heartwood rots represent threats to the trees. Additionally, some forms produce prickly foliage, which some people may find undesirable.