Aspens, Populus tremuloides, are generally small, beautiful trees known for their quaking leaves, intense yellow fall color, and beautiful white bark. They generally prefer moist areas and are found in the Sierra and the Rockies, as well as other areas. Something few people know about aspens is that they reproduce almost entirely underground by 'suckers' and 'cloning'. If you see a large stand of aspen, they may in fact be one genetically identical organism, connected underground via roots. Some of these clones cover many acres and are considered to be among the biggest life forms on Earth.