The araucaria family (Araucariaceae) includes some of the most remarkable conifers on earth. They are tall trees native to forested regions of South America and Australia. In majestic size and beauty, they certainly rival the coniferous forests of North America and Eurasia. In fact, they are considered the southern counterpart of our northern pine forests. Fossil evidence indicates that ancestral araucaria forests date back to the age of dinosaurs. In fact, the magnificant trees of Petrified Forest National Park in Arizona came from ancient forests of this plant family that lived more than 200 million years ago. It has been suggested that Baltic amber and the European gemstone called jet originated from ancient araucarian forests, but there is also evidence that other conifer families may have been involved in the formation of these vast deposits.

The Araucariaceae contains three remarkable genera of cone-bearing trees: Araucaria, Agathis and Wollemia. The type genus Araucaria is derived from "Arauco," a region in central Chile where the Araucani Indians live. This is also the land of the "monkey puzzle" tree (A. araucana), so named because the prickly, tangled branches would be difficult for a monkey to climb. Fossil evidence indicates that ancestral araucaria forests resembling the present-day monkey puzzle date back to the age of dinosaurs. In fact, it has been suggested that the tree's armor of daggerlike leaves was designed to discourage enormous South American herbivorous dinosaurs, such as Argentinosaurus weighing an estimated 80 to 100 tons! Another ancient South American species called pino paraná or paraná pine (A. angustifolia) grows in southern Brazil and Argentina. Three species of Arucaria are shown in the image to the right.

There appears to be some disagreement whether we have both Norfolk Island and Cook pines in southern California. In fact, many older references list only the Norfolk Island pine. The Norfolk Island pine typically has well-spaced, tiered, horizontal limbs and a distinctive silouette that is easy to spot from a distance; however, there are also trees with more closely-spaced limbs and a columnar, slender crown resembling the Cook pine. According to Trees of Hawaii by Angela Kepler (1990), most of the trees called Norfolk Island pine in Hawaii are actually Cook pines. They are naturalized throughout the Hawaiian Islands and have been exported as container-grown "Christmas trees" to the U.S. mainland. So it looks like some our southern California Norfolk Island pines are actually Cook pines, particularly if they were imported from Hawaii.

Norfolk Island Pine (Araucaria heterophylla)

Norfolk Island Pine (Araucaria heterophylla)

In general, the interval between tiers of limbs is greater on the Norfolk Island pine, particularly on younger trees. In addition, the horizonal limbs are longer than those of the Cook pine. The Cook pine has a slender, spire-like crown with shorter, more closely-spaced horizontal branches. Throughout southern California, there are trees with branching intermediate between the two previous species. The leaf shape and size is variable and not very useful in separating these two species. Some authors have suggested that the bark of cook pine exfoliates into larger flakes. This appears to hold true in the Palomar College Arboretum; however, I have seen trees with intermediate bark flakes. In fact, trees in southern California with intermediate characteristics between the two species may be hybrids.

Cook pines (Araucaria columnaris) in the northern hemisphere exhibit the peculiar habit of leaning in a southerly direction. In the southern hemisphere the trees commonly lean in a northerly direction. Matt Ritter of California Polytechnic State University, San Luis Obispo and a team of coauthors including Jason W. Johns , Jennifer M. Yost , Dean Nicolle and Boris Igic published an article in Ecology Volume 98 (September 2017) entitled "Worldwide Hemisphere-Dependent Lean In Cook Pines." They studied 256 Cook pines scattered across five continents and collected tree data at 18 locations between latitudes of 7°- 35°north, and 12°- 42°south. The median lean for all trees measured is 2.42 m away from the base, and the median tree height is 18 m, resulting in an 8.05° lean angle. The Leaning Tower of Pisa has a lean angle of 3.99 degrees. Unlike other species of Araucaria, and other conifers in general, their data showed that Cook pines in both hemispheres lean toward the equator. The Ritter team offered several plausible hypotheses for this unusual leaning habit. Cook pines originally come from New Caledonia, a tropical archipelago in the southwest Pacific Ocean. The trees were first classified during Captain James Cook's second voyage to circumnavigate the globe. The leaning habit in cultivated trees is so pronounced that it is often used to separate Cook pines from other similar species of Araucaria. Plant stems exhibit positive phototropism & negative geotropism and tend to grow toward light and away from gravity, while roots exhibit positive geotropism & negative phototropism and grow toward gravity and away from light; however, there are exceptions, such as parasitic mistletoes. Non-vertical shoot growth can be caused by mechanical force from wind or snow. Latitude appears to be a factor in the leaning of Cook pines, the further away the trees grow from the equator, the greater the slant. So possibly leaning has something to do with sunlight. Even if young trees of most species develop a tilt towards the sun, as the tree matures, it tends to correct this asymmetry and grow upwards, unless there's an environmental force preventing this, such as strong prevailing winds in one direction. But for some reason, A. columnaris trees just keep on tilting, no matter how tall they grow. And they even appear to be unique in this regard, because other Araucaria species from New Caledonia can stand up straight no matter where in the world they are planted. According to Ritter, et al (2017), studies on the research plant Arabidopsis thaliana have identified several gene families whose regulation effects phototropic and geotropic growth; however, the mechanisms controlling the expression of these genes are not well understood, especially for woody species. The mechanisms for directional lean in A. columnaris may be related to the incidence angles of annual sunlight, gravity, magnetism, or any combination of these. Another possibility is that the lean is non-adaptive, or even harmful, and may be caused by deleterious alleles in this species. Continued research on this fascinating conifer species may reveal some answers to these perplexing hypotheses, possibly resulting in a new scientific theory on plant growth. Stay tuned!  J.W. Johns, J.M. Yost, D.Nicolle, B. Igic and M.K. Ritter. 2017. Ecology 98 (9): 2482-2484.  Login To The Ecological Society of America: 1850 PDF Download: $49.00  Login For Palomar Staff: Through JSTOR & Palomar College Library

Phylogenetic studies comparing chloroplast DNA in the Araucariaceae show that the Norfolk Island pine's closest relatives are a clade of 13 species of Araucaria endemic to New Caledonia, including the Cook pine (A. columnaris). See: American Journal of Botany Vol. 85 ( No. 11): 1507-1516, 1998. Although New Caledonia is a relatively small island of only 19,000 square kilometers, it contains a rich conifer flora of 43 endemic species. In fact, 13 of the 19 species of Araucaria and five of the 13 species of Agathis are endemic to this island. Other rich conifer areas include New Zealand and the Sichuan Province of Western China. California is also a rich conifer region with 33 species in the pine family (Pinaceae), 2 species in the yew family (Taxaceae), 2 species in the redwood family (Taxodiaceae), and 16 species in the cypress family (Cupressaceae). In fact, 20 of the more than 100 pine species (Pinus) on earth are native to California.

According to M.G. Buck and R.H. Imoto (1982), Norfolk Island and Cook Pines were introduced to Hawaii in 1860. The two species probably hybridized and were subsequently dispersed throughout the islands. All juvenile trees today show A. columnaris traits and should probably be labeled as A. heterophylla x columnaris. The trees are propagated by seedlings, and if these are exported to the mainland, it is possible that some of our cultivated specimens are hybrids. Research forester P.G. Scowcroft (1988) states that Araucaria columnaris is the most abundant Araucaria species in the Hawaiian Islands, and that A. heterophylla is sparsely represented in Hawaii. According to Elbert L. Little, Jr. and R.G. Scolmen (1989), some exported seeds may be hybrids; however, hybridization is unlikely because the two species shed pollen six months apart. in addition, seed and foliage samples sent to Kew Gardens were all identified as A. columnaris. Dr. Little also states that seeds of A. heterophylla are larger, with a "swollen body to one cm thick." The four cotyledons on seedlings are also wider, 3 to 5 mm compared with 1.5 for A. columnaris.

• Buck, Michael G. and Roger H. Imotos. 1982. "Growth of 11 Introduced Tree Species on Selected Forest Sites in Hawaii." Pacific Southwest Forest & Range Experiment Station Research Paper PSW-169. Forest Service, U.S. Department of Agriculture. 12p.

• Little, E.L., Jr., and R.G. Scolmen. 1989. Common Forest Trees of Hawaii. Agriculture Handbook No. 679. Forest Service, U.S. Department of Agriculture.

• Scowcroft, Paul G. 1988. "Germinabiliy of Cook Pine (Araucaria columnaris) Seeds under Different Storage Conditions." USDA Forest Service, Pacific Southwest Forest and Range Experiment Station, Institute of Pacific Islands Forestry, Honolulu, Hi.

A. Tecate cypress (Hesperocyparis forbesii), B. Sargent cypress (H. sargentii), C. Piute cypress (H. nevadensis), D. Cuyamaca cypress (H. stephensonii), E. Santa Cruz cypress (H. abramsiana, F. Monterey cypress (H. macrocarpa), G. Gowen cypress (H. goveniana), H. Mendocino cypress (H. pygmaea), I. Macnab cypress (H. macnabiana), J. Modoc cypress (H. bakeri), K. Smooth-bark Arizona cypress (H. glabra), L. Rough-bark Arizona cypress (H. arizonica), M. San Pedro Martir cypress (H. montana), N. Mexican cypress (H. lusitanica), O. Italian cypress (Cupressus. sempervirens), P. Sahara cypress (C. dupreziana), Q. Kashmir cypress (C. cashmeriana), R. Mourning cypress (C. funebris), S. Port Orford cedar (Chamaecyparis lawsoniana), T. Nootka cypress or Alaska cedar (Xanthocyparis nootkatensis), U. Leyland cypress (Xanthocyparis x leylandii) also listed as Cupressocyparis leylandii and Cuprocyparis leylandii) in nursery trade. Note: The Port Orford cedar (S) remains in the genus Chamaecyparis, while the and Alaska cedar (T) is now placed in the genus Xanthocyparis, while the Leyland cypress (U) becomes Xanthocyparis x leylandii or Cuprocyparis leylandii in some references. Groupings of species, such as Hesperocyparis, Xanthocyparis, Chamaecyparis, Juniperus and Old World Cupressus represent separate branches (clades) in computer-generated phylogenetic trees.