True Cypresses

Although many different tree species include the word “cypress” in their common name, the true cypresses are a closely related subgroup of these trees.

Historically, the term “true” cypresses referred to conifers of the genus Cupressus. However, the classification scheme for these trees and their close relatives has been revised several times, and different authorities often present conflicting taxonomic arrangements.

Taxonomy and Species

Using the most inclusive definition, the genus contains about 26 species. These form several sub-groups, which some scientists recognize as either genera or subgenera. Most of the modern work conducted to illuminate the relationships among the various members of the group has relied on DNA analysis.

  • One group is comprised of all but one Old World Species. Some researchers call this group the genus or subgenus Cupressus.

  • Another group is comprised of all but one New World species. This group often goes by the genus or subgenus Hesperocyparis.

  • The Vietnam cypress (C. vietnamensis) is sometimes placed in its own genus or subgenus, named Xanthocyparis.

  • The Alaskan yellow cedar (C. nootkatensis) is sometimes assigned to the genus or subgenus Callitropsis.

Many members of the genus occur in small, isolated geographic areas. The differences between these populations are often subtle, leading different workers to reach different classification-oriented conclusions.

Description and Variation

Regardless of the taxonomic scheme in use, true cypresses bear several obvious physical similarities, although they may grow as either shrubs or trees. A few species are capable of attaining very large sizes — the Alaskan yellow cedar may approach 200 feet in height.

While the various forms often share a similar appearance and form, others grow uniquely. For example, the Monterey cypress (Cupressus macrocarpa) often develops a flat-topped canopy, courtesy of the strong winds that dominate in their cliff-side habitats. Conversely, the Arizona cypress (Cupressus arizonica) a close relative found a few hundred miles inland, produces a conical canopy, as it is not subject to intense, constant winds. Additionally, being better adapted to the hot summers of its homeland, the Arizona cypress is not as susceptible to cypress canker, which often afflicts Monterey cypresses forced to cope with hot summers.

The Mexican cypress (Cupressus lusitanica) is a popular ornamental species, which tolerates hot temperatures and droughts. The Gowen cypress (Cupressus goveniana) and the Mendocino cypress (Cupressus pigmaea) are two California natives, but various authorities classify these enigmatic forms differently. Both forms are closely related, variable and often grow in the same locations.

The Alaskan yellow cedar is found along the Pacific Coast as far south as northern California. The pendulous branches of these graceful cypresses make them popular ornamental specimens. Many of the trees growing at northern latitudes require a thick layer of snow to shield the roots from the bitter cold of Alaska’s winters. Because the amount of snow has decreased in recent years, these trees have begun suffering from frost damage.

Ecology

The true cypresses are native to several different regions of the world. They live from the temperate forests of Canada and the United States, down along the western portion of the continent into Mexico and Central America. They are also found in the Middle East and Northern Africa, and throughout the Himalayan region to China and as far south as Vietnam.

The tree’s globular seed cones develop over a period of 1 to 2 years, and many only open and release their seeds after the parent tree has been killed in a fire. The evergreen leaves are scale-like, and are superficially reminiscent of arborvitae leaves. Like some other conifers, the young leaves may be awl-shaped and pointed.

Cultivation

The widely planted Leland cypress (Cupressus × leylandii) is a hybrid tree created by the crossing of the Monterey cypress and the Nootka cypress (Cupressus nootkatensis). While the weak-wooded tree has largely fallen out of favor among arborists, the tree is still valuable in some cases, as it grown remarkably fast and is tolerant of a wide variety of soil types.