- Division: Pinophyta
- Class: Pinopsida
- Order: Pinales
- Families: Pinaceae (pines), Araucariaceae (araucarias), Podocarpaceae (podocarpus or yellow-wood), Sciadopityaceae (umbrella pines), Cupressaceae (cypress), Cephalotaxaceae (plum yew), Taxaceae (yew)
- Genera: 68
- Species: 629
Conifers have a long and noble history. They have been around since the days of the dinosaurs—in fact, 150 million years ago they were the most prevalent plants in the landscape, since flowering plants had not yet come into their own. Conifers belong to a large, hardy group of plants that produces seeds in the protected, tightly clustered structures we know as cones, which are actually the tree’s fruit. Although many people think of them as cold-weather plants, conifers can thrive in many different climates, including the tropics.
Both the largest living tree and the oldest living tree are conifers. The General Sherman Tree, a giant sequoia found in California’s Sierra Nevada Mountains, is more than 270 feet (82.3 meters) tall, with a trunk that measures 36 inches (91 centimeters) in diameter at the base. A bristlecone pine Pinus aristata in the Wheeler Peak area of Nevada is more than 4,900 years old—older than most human civilizations. The Safari Park’s Conifer Forest, which displays more than 1,000 plants representing 400 species of conifers, also has an important claim to fame: it is home to one of the few North African cypresses Cupressus dupreziana left in the world.
All but 15 species of conifers are evergreen, one of the familiar characteristics of this group of plants. They grow with a straight, central trunk bearing circles of horizontal branches, and the branching may become increasing complex as the tree gets older. Conifers also have a wide variety of distinctive bark. This outer layer typically starts out smooth, and some species stay that way, like lacebark pine Pinus bungeana or common yew Taxus baccata, with bark that peels or flakes off the older layers. Other species like redwood Sequoia sempervirens and incense cedar Calocedrus decurrens develop fibrous bark that grows in vertical strips. Still other species have thick, rough, blocky bark that can show a variety of colors, such as Douglas fir Pseudotsuga menziesii and Cedar of Lebanon Cedrus libani.
Contemplating Cones: The name conifer means “cone-bearer,” and the classification of conifers is often based on the structure of their cones—or whether they have them, since not all conifer species do. Those with cones have two types, a pollen cone and a seed cone. The pollen cones are soft and small, and they contain pollen sacs filled with pollen grains. Seed cones are the much larger, often woody, and easily recognized female cones that develop the seeds. These cones are usually made up of a spiral arrangement of little plates called scales. Pollination is often achieved by wind or water, carrying pollen grains to a seed cone. At maturity, seed cones may release their seeds by opening up as the scales spread apart; the scales shattering; or being burned by fire and snapping open. There are also species with seed cones that soften and change color to entice animals to eat them and spread the seeds, including podocarpus and juniper.
A Needling Question: Conifers are divided into many subgroups, including pines, firs, larches, and spruces. How can you tell them apart? There are some tricks of the trade to help identify which is which. Pine and larch trees grow needles—which are modified leaves—in bundles. Pines have two to five needles per bundle, while larches have 10 or more needles to a bundle. When needles are removed from a fir tree, a small, round scar remains on the twig. If they are removed from a spruce, a small, woody peg is left standing out from the branch. And then there are the conifers that surprise you, since they have broad leaves instead of needles, like the Kauri pine Agathus robusta and the gingko tree Gingko biloba, which is considered one of the most primitive of the conifers.
About a third of all conifer species are considered threatened or vulnerable throughout their range, and 20 species are critically endangered. The three main categories of threats facing conifers in their natural habitats are loss of the habitat to agriculture and development; deforestation and cutting the trees down for timber, paper, and fuel; and the effects of global climate change, including increased frequency and severity of fires, pollution, and increased losses from pests and disease.
Conservation efforts for conifers include continued protection and maintenance in reserves and national parks; cultivation and propagation in botanical gardens and collections to preserve species and genetic biodiversity; and working against the devastating effects of deforestation and climate change to keep the viable forests that remain.
The San Diego Zoo and Safari Park grow and care for a variety of conifer species on our grounds. Our horticulture staff and researchers also maintain seeds from endangered and threatened conifer species in our Institute for Conservation Research Seed Bank, and are involved in conifer conservation and restoration projects.
North Africa Cypress
In the wild, this rare species is only found in Algeria, on the Edeni plateau of the central Sahara. It is one of the most drought-tolerant and frost-resistant conifers, and yet it is critically endangered, exploited for centuries for its wood. However, efforts to sustain and reintroduce this beautiful cypress began in 1987.
This endangered species is a Southern California native, found only in the Santa Ana Mountains of Orange County and San Diego County, as well as in northern Baja California, Mexico. With its limited range, the species has been severely impacted by wildfires in the past 15 years and is threatened with extinction. It is one of the plant species that San Diego Zoo Global is working to save, storing seeds and propagating and planting seedlings in protected areas.
Found throughout the Mediterranean region, this cypress is drought tolerant and is resistant to dust, sleet, and air pollution. It can live to be 1,000 years old and has frequently been used for archeological dating at sites in Italy and Israel.
The languid silhouette of the bald cypress is famous in the southern United States, where these trees flourish in swampy areas. It has an extensive root system—including lateral roots that combine with the trunk to give it a buttressed appearance—that makes it very stable, even in hurricanes. Ospreys and bald eagles sometimes build their nests in the spreading canopies of older trees. The seed cones are relatively inconspicuous on this species, but clusters of 3- to 5-inch-long (7.6- to 12.7-centimeter) pollen cones drape along the needles like decorative fringe.
Native to Tibet, this beautiful tree has flat sprays of leaves that are blue-gray and hang from graceful, drooping branches, creating the look of a misty waterfall.
If you’ve ever traveled to Northern California’s Muir Woods, you’ve encountered the coast redwood, considered one of the tallest trees in the world. Mature, centuries-old individuals of these forest giants can reach heights of more than 350 feet (107 meters), with fragrant foliage of light green to deep blue-green and the characteristic red-brown trunk. The oldest coast redwood on record was counted by its rings to be 2,200 years old.
The giant sequoia is sometimes confused with the coast redwood, and they share the spotlight in California, where they are both the state tree. Giant sequoias can grow to 325 feet (99 meters) and are hardy against cold, with dense foliage.
Native to China, this endangered conifer species was first described in 1941 only from fossils and was thought to be extinct. Yet in that same year, a forester came across a large living tree but did not connect it to the fossils that had been described. The tree became part of a shrine, and the local villagers called it the “water fir.” It wasn’t until 1946 that the connection was discovered, and in 1948, Harvard University funded an expedition to see the living tree. Seeds were collected, and seedlings and seeds were then distributed to various universities and arboretums, bringing back this ancient species.
Cedar of Lebanon
One of the most famous of the cedar species, this tree is described in the Old Testament as “excellent above all trees of the field.” It is thought that wood from this cedar was used to build King Solomon’s temple, and the most famous grove stands today about 15 miles outside Beirut. The Horsh Ehden nature preserve in Lebanon is also a site where these ancient trees can be admired.
Blue Atlas Cedar
Arranged along the branches in clustered starbursts, the silvery blue needles make this a favorite ornamental tree among gardeners. This true cedar is named after its native range in the Atlas Mountains of Morocco and Algeria. Its unusual, barrel-shaped cones sit on the tops of the branches, looking like glossy brown decorations.
This species is also called the bigcone pine, because its seed cones can be 14 inches (35.6 centimeters) long and weigh up to 4 pounds (1.8 kilograms) each. This tree is native to California and Baja California, Mexico, where it makes its living on dry, rocky slopes and chaparral. It is a fast grower that can reach heights of 90 feet (27.4 meters).
Mexican Weeping Pine
This conifer gets its common name from its long, drooping needles, and one of its local names is pino triste, the sad pine. This species is drought tolerant but is easily killed by fire. Nature remedied that by making sure the scorching opened the cones to release the seeds, which are carried by papery “wings” in the breeze to root elsewhere.
This unusual tree is a tropical species found mainly in Queensland, Australia. It managed to survive through a tumultuous past at the whims of loggers, especially during wartime when the tree was cut down extensively for use in construction. Conflicts arose between those wanting to exploit stands in Queensland's Danbulla State Forest and those wanting to protect them, until the Forestry Department stepped in with girth limits that slowed the logging.
The silhouette of these trees against the ocean sunset is one of the signature sights of the Del Mar and La Jolla coastal communities in San Diego. Yet, this picturesque species is threatened with extinction. Without the protection of a local visionary, Miss Ellen Browning Scripps, the Torrey pines might have disappeared forever. In the early 1900s, she bought the land where the majority of the trees stood, now designated as Torrey Pines State Park, where the pines continue to survive on the windblown, sandstone cliffs.