While you make a trip to Aspen, you should explore some more in the state of Colorado. Know Before You Go. Please...
Aspen Foliage
Quaking Aspen
Aspen are remarkable and unique trees. In fact they are so different that it may be better not to think of aspens as trees. First of all, a stand of aspen is really only one huge organism where the main life force is underground. Think of aspens as large 1-20 acre systems of roots that remain hidden underground until there's enough sunlight. (source: http://www.nps.gov/)