I learned some new science on this trip: the most massive living organism in the world is a grove of quaking aspen trees in central Utah. The grove is made up of thousands of trees, but they are not individual trees; they all share a single root system and are genetically identical. The whole collection is considered a single living organism called Pando (Latin for "I spread.") Read more about it here.
The grove was not easy to find (no address, just directions within a very large park on dirt roads) but worth the search. I've always loved aspen trees, and these were in peak form, leaves shimmering gold in the autumn sun.
Fishlake National Forest, Richfield, Utah