In Utah there is a Quaking Aspen that is the largest single organism in the world.

Pando is believed to be the largest, most dense organism ever found at nearly 13 million pounds. The clone spreads over 106 acres, consisting of over 40,000 individual trees. The exact age of the clone and its root system is difficult to calculate, but it is estimated to have started at the end of the last ice age (2.6 million years ago). Some of the trees are over 130 years old. It was first recognized by researchers in the 1970s and more recently proven by geneticists. Its massive size, weight, and prehistoric age have caused worldwide fame.