Populus tremuloides is a deciduous tree native to cooler areas of North America. The species is referred to as Quaking Aspen, Trembling Aspen, and Quakies, names deriving from its leaves which flutter in even a slight breeze. The tree can become tall, up to 25 meters, but is more often half that height, with smooth pale bark scarred with black. The glossy green leaves, dull beneath, become golden to yellow, rarely red, in Autumn. The species rarely flowers, often propagating through its roots to form large clonal groves. The quaking or trembling of the leaves is due to its flattened petioles. The specific epithet, tremuloides, is given for this trembling characteristic. Other species of Populus have petioles flattened partially along their length, while the Quaking Aspen's are flattened from side to side along the entire length of the petiole. This quaking of the leaves produces a soft sound that many consider a hallmark of the Quaking Aspen. It can be found in many parts of North America. In California it is most common in the Sierras and other high elevation mountains. Nurseries usually sell only male plants because female plants can produce large amounts of cottony seeds. Unless you have acreage, use caution in planting this tree because it will send out suckers long distances to quickly form a dense grove that will fill in any moist area. There are usually few understory plants in Quaking Aspen groves.