Pando (or The Trembling Giant) is a clonal colony of a single male Quaking Aspen (Populus tremuloides) located in the U.S. state of Utah, all determined to be part of a single living organism by identical genetic markers and one massive underground root system, although whether it is a single tree is disputed, as it depends on one's definition of an individual tree. The plant is estimated to weigh collectively 6,000 tonnes (6,615 short tons), making it the heaviest known organism. The root system of Pando is claimed by some to be among the oldest known living organisms in existence at 80,000 years of age.
Pando is located in the Fishlake National Forest, near Fish Lake on the Fish Lake Plateau located at the western edge of the Colorado Plateau in South-central Utah. The name "Pando" was chosen because it is Latin for "I spread."
Pando is thought to have grown for much of its lifetime under ideal circumstances: frequent forest fires have prevented its main competitor, conifers, from colonizing the area, and climate change, transitioning from a wet and humid weather pattern to semi-arid, has obstructed widespread seedling establishment and the accompanying rivalry from younger aspens.
Pando was discovered by Burton V. Barnes of the University of Michigan in the 1970s. Barnes was widely considered an expert on North American aspen at the time, having been one of the first to describe the clonal growth of aspen from an extensive root system as part of his dissertation at Michigan in the late 1950s. Barnes had described Pando as a single organism based on its morphological characteristics. Building off of Barnes's earlier work, Michael Grant of the University of Colorado at Boulder re-examined Pando and claimed it to be the world's most massive organism in 1992.
In 2006 the United States Postal Service made a stamp in commemoration of the aspen, calling it one of the forty "Wonders of America."