A single 'tree' in Utah that's actually one clonal organism — 47,000 stems sharing a single root system. ~80,000 years old.
From Wikipedia
Pando is the name of a quaking aspen clone located in Sevier County, Utah, United States, in the Fishlake National Forest. A male clonal organism, Pando has an estimated 47,000 stems (ramets) that appear to be individual trees but are genetically identical parts of a single tree connected by a root system that spans 42.8 ha. As a multi-stem tree, Pando is the world's largest tree by measures of weight, landmass and species, and is generally held to be the world's single largest organism by weight.