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PLANTS OF YELLOWSTONE NATIONAL PARK 
Quaking aspen ( Populus tremuloides) —This is the most common 
broad-leaved tree in the park. It often develops abundantly after a 
forest fire and forms dense groves, especially in moist places. The 
leaves are rather small and roundish heart-shaped with a short, sharp 
point and small regular teeth. The petiole is flattened laterally 
and this causes the leaf to tremble with the slightest breeze. The 
bark of this tree is the favorite food of the beaver. 
Figure 32.—Quaking aspen. Photograph hy George Grant, National Park Service. 
Balsam poplar ( Populus balsamifera) .—Leaves ovate with heart- 
shaped base, dark green above and pale beneath, and with small, 
rounded teeth. The buds are fragrant and sticky. 
Narrowleaf cottonwood {Populus angustifolia,) has narrowly lance¬ 
shaped leaves which are rounded at the base and have fine rounded 
teeth along the entire margin. 
Sargent cottonwood {Populus sargentii) has also been reported as 
occurring in the park. 
Willow {Salix). —There are several kinds in the park but they are 
rather difficult to distinguish, and most park visitors are not 
