Aspen
It forms large stands (groups) of genetically identical trees (clones) connected by a single underground root system. These trees form through root sprouts coming off an original parent tree. The largest known fully connected aspen is a grove in Utah nicknamed 'Pando', and some experts call it the largest organism in the world, by mass or volume. It covers 0.43 km2 (106 acres) and is estimated to weigh .