Salix humilis Marshall
Family: Salicaceae
prairie willow, upland willow
Salix humilis image
from USDA Plants website  
Etymology: Salix: Latin name for the willow and meaning "to leap or spring" in reference to its fast growth
Plants: perennial shrub 3 1/2'-10' tall, forming clones
Leaves: obovate to obovate-lance-like, edges slightly in-rolled, underside whitened
Flowers: mostly stalkless, curving catkins
Habitat: dry, medium moisture to wet; open woods, barrens, prairies
Conservation Status: Native