Botanic Superlatives: The Largest Forest of One

Botanic Superlatives: The Largest Forest of One

February 11, 2011
Photo by: Scottks1/Flickr

Pinning a first-place ribbon on a plant can be difficult and an exercise in semantics. In today's case: What constitutes a single tree? If a tree is defined as that which shares a root system, the quaking aspens (Populus tremuloides) of Utah's Fishlake Forest should be awarded 47,000 blue ribbons that read "World's Largest Tree." That's the number of discrete tree stems that constitute Pando (Latin for "I spread"), a colony of genetically identical aspens that converge underground in a single sprawling root system. 

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This changes things, doesn't it? If a tree's allure is derived from its noble solitude, with its admirable "I, against the world" endurance, well then, the aspen is not a tree at all. Think about it. How often have you seen a single aspen tree? Probably rarely—aspens are more like a collective of fraternal siblings whose vitality remains centrally united. The story starts with a single seedling, which grows a root system. Tall trunks emerge from the root when adequate sunlight coaxes new growth, and before long a forest of aspens is born: a striating pattern of thin white lines against a canopy of glossy green leaves that glow golden in the autumn sun. (The significance is more than aesthetic: colonies change color at varying times in the season, providing a way to tell them apart.)

Above ground, each tree can live for a century; below ground, the root system can endure for tens of thousands of years. It endures the death of individual trees, and sets forth new growth when the time is right. An unusually cloudy year? That's okay, the underground aspen roots can lay dormant for a very long time. As it happens, they might prefer to wait until a fire passes through and sweeps bare the landscape. After such a burn, sunlight has an unobscured path to the forest floor, and the aspen roots waiting below.

Photo by: B. Campell; Aspen post-fire regrowth, Fish Lake Forest, Utah

Let's return to Pando, and its superlative metrics. Arborist purists might withhold the award for largest tree, but no matter—Pando is considered the largest known organism. With a footprint surpassing 100 acres, and weighing in at more than 14 million pounds, the graceful congregation is a surprising heavyweight champ. Similarly, its alternate title—The Trembling Giant—is hardly the epithet of a contender. But it is accurate. All quaking aspens are named for their frenetic leaves, audibly fluttering with the slightest breeze (a consequence of their unique leaf structure). Utah's Pando is no different, and the effect is a giant that trembles softly in the forest. 

Anna Laurent is a writer and producer of educational botanical media. Photographs from her forthcoming field guide to Los Angeles are available for exhibition and purchase at the author's shop