By Doug Nichols
Have you met one of Colorado’s oldest living residents? No, it is not that cranky, old guy down the street; it is the bristlecone pine. They are among the oldest living organisms anywhere in the world. There are some bristlecone pines in Berthoud, but they are just youngsters. The really old ones — some more than 1,500 years old — live in the Rocky Mountains.
The Colorado bristlecone pine (Pinus aristata) is sometimes known by the common name foxtail pine. The oldest bristlecone pine in our state lives on Mount Evans and is reported to be at least 2,435 years old, based on its number of annual tree rings sampled using a coring device. Bristlecone pines have dark green to blue-green needles in bundles of five, and there are characteristic white resin flecks on the needles. The bundles of needles grow densely along the branches giving them a form reminiscent of a fox’s tail.
The cones that give the tree its name are ovoid-cylindrical in shape, 2 to 4 inches (5-10 cm) long by 1 to 1.5 inches (3-4 cm) when closed and more than 2 inches wide when mature and open. They have numerous thin scales, and each scale has a bristle-like spine. The winged seeds, which are released when the cones open, are less than an inch long. Most seeds are dispersed by the wind, but Clark’s Nutcrackers (birds of the crow family also living in the Rockies) pluck some from the cones for food. These birds also store seeds for later use, but some uneaten seeds, along with those dispersed by the wind, can possibly grow into bristlecone pine seedlings to begin exceptionally long lives.
In cultivation, bristlecone pines can grow to 20 feet tall and up to 10 feet wide. Cultivated trees rarely live more than 100 years before being killed by root decay in the warm, moist conditions of yards and gardens. Bristlecone pines do not require much water, which seems to be one of their secrets of longevity.
The really old specimens living high in the mountains tend to be gnarled and twisted. Because of cold temperatures, dry soil, high winds, and short growing seasons in the Rockies, bristlecone pines grow very slowly. They dwell in an environment where practically nothing else can survive, so they have little competition for water and nutrients. They are exceptionally drought-resistant, and have dense, highly resinous wood that is a barrier to invasion by insects, fungi, and bacteria. Sparse ground cover reduces the threat of fire. Thus, they cling to the rocky soil in isolated groves at and just below the tree line and patiently endure for hundreds or thousands of years.
In addition to Colorado, Pinus aristata is native to the Rockies of northern New Mexico and the San Francisco Peaks of northern Arizona. Another species of bristlecone pine, Pinus longaeva, is found in the White Mountains of eastern California, and this species lives even longer than our Colorado bristlecone. The oldest surviving member of that species is 4,841 years old this year.
Doug Nichols is a Scientist Emeritus with the U.S. Geological Survey and a Research Associate with the Denver Museum of Nature & Science. He is a resident of Berthoud. Send comments to Recorder.Science.Guy@gmail.com.