Cypress-pines are small- to medium-sized trees, although a few species reach heights in excess of 100 feet. Although they resemble junipers (Juniperus spp.) in general appearance and by virtue of possessing two different types of leaves, cypress-pines bear both needle-like and scaly leaves throughout their lives.
Name and Classification
The genus name of cypress-pines comes from the Greek words meaning “beautiful” and “three,” which refers to the thrice-whorled leaves and cones that adorn the trees.
Although they are somewhat similar to pine trees, cypress-pines have no special allegiance to the pine tree clade (Pinus spp.). Instead, they are firmly nested within the cypress family (Cupressaaceae). Accordingly, many tree professionals are beginning to drop the “pine” portion of their name, instead simply referring to them as cypresses.
Fifteen species comprise the genus Callitris; two are native to New Caledonia, while the remaining species inhabit Australia. They are relatively rare outside of the South Pacific, although they have established themselves in some portions of Florida, where they now grow wild.
Reproduction and Ecology
Cypress-pines produce small, woody cones that bear about 30 to 40 seeds. As monoecious plants, cypress-pines produce both male and female cones occur on the same tree. All but one species grow in arid habitats; the outlier — Callitris macleayana — is native to Australia’s eastern rainforests.
Although most cypress-pine species grow in areas plagued by fire, they exhibit very little fire tolerance. After fires pass through an area and kill the majority of the mature plants, the next generation occurs as seeds, buried in the ground. Like some native California conifers, cypress-pine cones remain closed until a fire heats them enough to cause them to open and release their seeds. This way, the seeds usually land on a bare patch of ground, where they will experience limited – if any – competition.
Commercial Uses and Cultivation
The hard, compact bark of cypress-pines covers and protects the lightweight, aromatic wood underneath, which is the hardest wood among all softwood species. The wood has many useful commercial properties, and the wood of many species resists both termites and decay, even when not chemically treated. This makes the timber useful for outdoor applications, such as landscape timbers and playground equipment.
Gardeners often plant cypress-pines as ornamental plants, but they are extremely susceptible to brush fires. They prefer sandy soils and full sun, although the young will continue to grow – albeit slowly – when they sprout under the forest canopy. Most of the cypress-pines are more frost tolerant than other conifers of the southern hemisphere.
South Esk pines (Callitris oblonga) are the only members of the genus adapted for riparian habitats. Consequently, they are perhaps the most flood-tolerant members of the genus, although even though they strongly prefer well-drained soils. South Esk pines usually grow as large shrubs, but occasional specimens take on a tree-like form and reach 30 feet in height. Like most other representatives of the genus, South Esk pines are rarely cultivated in the United States, however a few botanical parks in California maintain specimens, and you may be able to find seedlings or seeds via commercial avenues.
White cypress pines (Callitris glaucophylla) are handsome trees that grow to about 90 feet in height. These plants are allelopathic, meaning they release chemicals into the soil that inhibit the growth of competitors. Accordingly, these trees rarely form pure stands. These trees are rather drought and frost tolerant, and thrive best in sandy, well-drained soil. Although the tree produces very shallow roots (which make it unsuitable for growing near other plants) it makes an excellent windbreak and helps to stop substrate erosion.
White cypress-pines are the most commercially important members of the genus, as they are harvested for their timber, as well as resin, oils and tannins. Northern cypress-pines also go by the scientific name Callitris glaucophylla.
The scrubby cypress-pine (Callitris canescens) is a drought-tolerant species, suitable for USDA Hardiness Zones 9a through 11. They are moderately drought tolerant, making them suitable for planting in parched environments. The largest member of the species, the stringy bark cypress-pine (Callitris macleayana) grows to incredible heights – occasionally exceeding 150 feet, making them largely unsuitable for private cultivation.