Botanical Category

• Aspen groves have a distinct sound due to their mobile, rustling leaves.Jupiterimages/Photos.com/Getty Images
  
  Quaking aspen is a specific species of poplar, while birch is an entire family of trees. Common birches include the river birch (B. nigra), a fast-growing native of the eastern United States, and the European white birch (B. pendula), a non-native tree with ghostly pale bark. Quaking aspen, on the other hand, is a single variety native to the western United States.
  
  

Leaves

• Quaking aspen leaves are round with minute, rounded serrations along the margins and a slightly pointed tip. They have long, flattened petioles, or stems, that act as airfoils and cause the leaves to tremble in the softest breeze. In fall, they turn a bright, clear yellow in frosty weather, but often simply fade to tan or mottled yellow at lower elevations. Birch species also turn yellow in the fall, but their leaves are more elongated than quaking aspens' and come to a distinct point. The leaf margins are finely but sharply serrated and the petiole is round.
  
  

Bark

• Many birches have peeling bark, while aspen bark is relatively smooth.Jupiterimages/Photos.com/Getty Images
  
  Young quaking aspen bark is smooth and powdery white. Knots and scars stand out in dark relief against the bark, and it contrasts strikingly against darker backgrounds. Birch bark varies from a rich brown to white, depending on the species. Paperbark birch (Betula papyrifera) has ivory to white bark that peels in large sheets. European white birch (B. pendula) also has white bark on its trunk and older limbs, but smaller branches are golden brown. River birch (B. nigra) has rosy young growth, but older bark is a golden brown that peels attractively as the tree ages, creating horizontal curls.
  
  

Growth Habit

• Quaking aspen prefer higher elevations and usually grow alongside mountain conifers.Comstock/Comstock/Getty Images
  
  Although they do produce seed, quaking aspen commonly spread through underground roots to create a genetically identical grove of trees -- a single clone may spread over 100 acres. They adapt to a wide range of growing conditions but are short-lived in warm climates. Aspen need little care and may become invasive. Birch, in contrast, are well-mannered but require regular moisture and protection from bronze birch borer, an insect that decimates birch trees. Both, however, often grow in dense groves.