Sure, the University of Colorado and the University of Utah may be rivals, but a less-publicized competition is also taking place between the two states. The result of this contest has even more at stake—the right to brag that the winner hosts the planet’s largest living organism.

Many biologists believe that the biggest of all Earth’s living organisms is an aspen grove. The white-barked aspen (populus tremuloides) reproduce through their roots, known as suckers, which send up new chutes that eventually grow up to become trees. In other words: Their root systems are completely interconnected. Entire hillsides can be covered by a single aspen organism. This means all of its leaves appear at the same time in the spring, and they also simultaneously turn gold in the fall, creating incredible foliage displays.

These clonal colonies are enormous; scientists estimate that the Pando grove in Utah’s Fishlake National Forest contains around 47,000 trunks, which collectively weigh more than 13 million pounds. By collecting leaf and bark DNA samples, researchers from Utah State University and the U.S. Forest Service confirmed in 2008 that Pando is a single genetic biomass, and therefore, they argue, holds the current title of largest living organism.

But the prize is up for debate. Aspen groves on Colorado’s Kebler Pass, northwest of Crested Butte, may be even larger. They just haven’t been fully studied yet, according to a 9News story.

Other Pac-12 rivals, including Washington and Oregon, want in on this game, too. In 1992, researchers announced the discovery of a honey fungus in Washington that has spread through 1,500 acres of tree roots. In 2003, Oregon one-upped the Huskies by unearthing an even larger specimen of the same type of fungus, which has spread across nearly 2,400 acres—the equivalent of 1,665 football fields—in eastern Oregon. Since 2008, however, the Utes’ aspen grove has topped the charts.

Enjoy it while you can, Utah, until Colorado swoops in for the win.

(Read more about the geological history of Colorado’s beautiful landscapes)

Terri Cook
Terri Cook
Terri Cook is an award-winning freelance writer based in Boulder. More of her work can be found at