Poplar (Aspen)

Is there a breeze today in this windy city? These trees are sometimes called "quaking aspen" because they have developed leaves with flattened stems, which allow them to "tremble" and flutter in the breeze. 

When broken down, aspen leaves produce "salicylic acid" one of the main ingredients in aspirin. For this reason, aspen trees have been used as painkillers for much of human history. 

Poplar trees don't always reproduce with seeds. If you ever find a group of these trees standing in a grove together, it's possible you've found a single organism of one massive root system that has sprouted up many genetic clones.