A Gardening Journal
Really Must Have: Monkey Puzzle Tree
- Published: December 28 2015
In August, I introduced this singular tree after discovering that an individual was surviving, improbably, near Buffalo. "Surely," my inner plant geek taunted me, "you can establish one of your own in Rhode Island. Are you the plant geek or not?"
Then, during a holiday visit to Washington, D.C., I paid a visit to another. Finally, one of these trees was, literally, right at hand.
Even free-standing out by the street—in other words, completely unsheltered—it was going gangbusters in this sunny spot in Zone 7. In such a benign climate, it wasn't just surviving, it was thriving: Even Winter's worst (cue the Winter of 2014 - 2015) wasn't severe enough to damage the tree's thick, stiletto-sharp needles.
Look at the shot, below, of a section of the tree's upper trunk. Each new stem of Araucaria araucana emerges tightly sheathed by needles. For some years as that stem matures and thickens, its initial complement of needles persists. Those needles are remarkably durable.
See the segment of trunk in the middle of the picture above? The increasing girth of the trunk has spread the needles apart—but evenly so: They still maintain their defensive encirclement. Notice, also, that the needles point upward. On an emerging stem, the tips of the young needles will of course be formed such that they point forward. As that stem becomes old enough that you'd call it a branch, that forward orientation also becomes outward.
Think back for a moment to this tree's common name, monkey puzzle. The thought is that these countless sharp-tipped needles would frustrate any climbing animal that would be drawn to the tree's coconut-sized cones and the large, tasty nuts they contain.
Is this plausible? Because the needles encasing the stems and branches point outward or even, on older branches, downward, if that animal were able to grasp the stems firmly between where one rank of needle points were and the emerging section of the next youngest rank, that pressure would depress those needles and, thereby smooth them out. A handhold or, rather, pawhold might be established on the resulting band of now-flesh-friendly stem. And then another. A clever, strong, and persistent animal might be able to ascend through the tree's branches.
Even so, eventually the trunk itself would be reached, and there the orientation of those forward-then-outward needles changes again, and for the worse: Then the needles are pointing upward. Plus, a slender stem that might have been fully graspable would now, as a major limb or trunk itself, be too thick. Although there is more space between the needles that persist on these thicker branches and so, potentially at least, that much more unprickly purchase for toes and fingers, the force of gravity ensures defeat. To make any upward progress, the animal would need to rest its toe pads atop the upward-pointing needles. Unless those pads were armor-plated, would such a perch be bearable?
And further upward progress would seem quite impossible: If one paw were released to grasp the next higher spot, the other three must support the animal's full weight for a moment—but while resting on those needle-sharp tips.
So, then, this conifer's treacherous foliage keeps its nuts safely out of reach at the top of the tree. Monkey puzzle tree: QED? Not likely. The name was proposed in England in the 1850s, when Araucaria was still a rare oddity in British gardens. This ancient tree's success through countless millennia in the Andes mountains of what are now Chile and Argentina didn't depend on puzzling—or pleasing—monkeys at all: None are native to the Andes.
Here's an entirely different explanation for this tree's aggressive self-protection, and how the tree as well as its nuts successfully interacted with wildlife ages ago when the species was assuming its current habits. Then, South America was home to quite a sideshow of "megafauna," such as species of sloth as tall as giraffes and armadillos the size of Volkswagen Beetles. These enormous animals' symbiosis with the avocado is now understood: They could gulp those fruits down whole—and excrete the enormous pits easily, and far enough away from the parent tree that the pits had access to sun and water.
Next, consider that Araucaria makes its nuts fully available to any creature wandering by—and when they are the ripest and most tasty, too. Yes, the cones are at the top of the tree, but when they are mature, they split open and release the now-ripe nuts, which drop easily to the ground. No one ever needs to climb a monkey puzzle to harvest the nuts. Just pick them up.
Plus, the just-fallen nuts are not only not poisonous, they are fully edible. But first you need to free them from their shells. If that ground sloth were scarfing down nuts by the pawful, the only way some of them would escape becoming digested is if the animal were eating so many at a time that some of the nuts didn't get chewed in the process but, instead, were swallowed whole. (Remember, these are large animals with correspondingly large gullets.) These uncracked nuts' shells would have protected them from digestion so that they could be excreted whole. As with the avocados, these megafaunal foragers acted as mobile seed distributors that also, conveniently, deposited those excreted pits, seeds, and nuts in piles of high-nutrient manure.
And what about those Araucaria needles? They encircle otherwise soft young shoots completely, and their painfully sharp tips all point forward. A browser with large enough claws—cue the giant sloth!—might be able to rip them from the trees, but how could they be swallowed? Wouldn't it be as painful as swallowing a porcupine? So wouldn't the probable purpose of the needles be to frustrate browsing, not climbing?
Perhaps the needles prevent browsing and climbing. Monkey puzzles don't reach sexual maturity until they are about twenty years old. Only if they were free from browsing when they were young would trees have a hope of growing long enough to bear nuts. And only if the trees were tall enough and forbiddingly armed enough—especially at the upper portions of the trunk, which is the only place the cones are produced—would the young nuts be impossible to reach by climbing, too.
A twenty-year-old monkey puzzle in its native habitat is likely to be even taller than the one I just visited in Washington: so tall, in fact, that its young cones would be too high for even megafauna to reach from the ground. No wonder current monkey puzzles don't start bearing for twenty years: The nuts of any that began bearing when the trees were younger—and, therefore, shorter—would probably have still been reachable. Few cones would have matured enough to be able to release viable nuts because they could all have been eaten right on the vine, as it were.
One of my garden goals for 2016 is to welcome Araucaria araucana to my garden. Because the climate here isn't quite Zone 7, I'll be espaliering my monkey puzzle against the west wall of my house. Stay tuned
Here's a look at some other monkey puzzle trees thriving in northeast North America as well as in their native habit in South America. I'm looking forward to profiling this sui generis conifer after it's performing well in my own gardens.