In the Garden: Dinosaur Trees
by Charles Kidder
If you’ve seen dioramas or CGI movies of dinosaurs roaming through a prehistoric landscape, you may have noticed tall, gaunt pine-like trees in the background. This potential dinosaur dinner, the genus Araucaria, was widely distributed and reached its maximum diversity some 200 million to 60 million years ago, but today is restricted to isolated populations in the Southern Hemisphere. Some of the herbivorous dinosaurs were the largest of their tribe, and some scientists posit that they evolved even longer necks to browse the foliage of these trees. Today, the dinosaurs are gone, but 19 species of Araucaria hang on, with 13 of those endemic to the island of New Caledonia east of Australia. Despite common names like Chilean Pine or Moreton Bay Pine for particular species, they are only distantly related to the true pines.
Most of us are probably familiar with one species, the Norfolk Island Pine, Araucaria heterophylla. Native to a tiny subtropical island of the same name a thousand miles east of Australia, we know it as a houseplant, often transformed with decorations at Christmas. It is also planted in gardens in warmer climates, where it can grow to 170 feet in height. The Cook Pine, A. columnaris, is widely planted in warmer climates, and it’s likely you would have seen it when visiting South Florida or Hawaii. It closely resembles the Norfolk Island Pine, but has denser branching and a very tight, columnar habit. This “Christmas Tree” shape, more akin to the spruces and firs of northerly latitudes, looks out of place in the tropics, where we are used to seeing either tall palms or wide-spreading trees like banyans.
The bunya-bunya, A. bidwillii, hails from Queensland, Australia and is planted in both the tropics and warm temperate climates. Perhaps its most distinguishing feature is its huge cones, over a foot in diameter and weighing more than ten pounds. For obvious reasons, botanical gardens cordon off the areas underneath these trees when they are dropping their cones. Imagine something bigger than a pineapple dropping on your head from eighty feet!
Among a clan of weird plants, the Monkey Puzzle tree (A. araucana) may be the most bizarre. Young plants have an open, pyramidal shape of preternatural symmetry; I have seen artificial Christmas trees that look more real. The branches, covered with “leaves” that are more like daggers or box-cutter blades, droop downward, then arch up toward the tip. Mature trees lose the pyramid shape and most of their lower branches; a flat top of foliage on a bare trunk gives an umbrella effect. Monkey Puzzles were popular with Victorian collectors, with their penchant for the unusual. When one British gent was showing his new acquisition to friends, one commented that, “It would puzzle a monkey to climb that!” These trees do not actually have to contend with monkeys in the wild, although some claim that their extreme spininess was a defense against those long-necked dinosaurs. Luckily for indigenous peoples of South America, it is not necessary to climb the trees to harvest its seeds. The cones drop and reveal large “pine nuts” that can comprise up to 15 percent of their diet during harvest time. The large quantity of nuts from a mature tree could offer potential as crop in the regions where it can be planted, although it does require a Monkey Puzzle thirty to forty years to mature.
Indigenous to a small stretch of the Chilean and Argentine Andes, Monkey Puzzles are also widely planted in cool temperate climates. You’re likely to see them in the Pacific Northwest, the UK and milder areas of Continental Europe. (Although I have observed them in the latter locations, I was disappointed at missing them in their native range on a recent trip across South America. An excuse to return?) But what about growing them in the Southeast? For us, cold should not be the issue, since Monkey Puzzles live in an area with cold, snowy winters; the real issue may be summer heat and humidity, along with poor drainage in clay soils. I have occasionally seen them in Southern arboreta, only to return a few years later, the Monkey Puzzle conspicuous by its absence. The best example I have seen in the East was at the gardens of the Barnes Foundation near Philadelphia. That was a good fifteen years ago, but a check of their website seemed to indicate that the tree was still there in late 2010.
Many of the Araucaria species’ natural ranges have been considerably reduced in recent times and some are classified as endangered. Their tall straight trunks were useful for masts and lumber, and nut harvesting limited reproduction. Fortunately some species now receive protection in national parks. Consider yourself lucky indeed if you can see any of the Araucarias in the wild, as you are witness to plants descended from the forests that dinosaurs roamed.