"Southern Wild Flowers and Trees." Alice Lounsberry.
For the Botany of the Rocky Mountain region use:
"New Manual of Botany of the Central Rocky Mountains." John M. Coulter; Revised by Aven Nelson.
"Rocky Mountain Wild Flower Studies." Burton O. Longyear.
"The Trees of California." Willis Linn Jepson.
For general information regarding the shrubby plants of the United States use:
"Our Shrubs of the United States." Austin C. Apgar.
"Our Northern Shrubs." Harriet Louise Keeler.
For the wild flowers outside of those already mentioned for the Southern United States and the Rocky Mountain region use:
"Our Garden Flowers." Harriet Louise Keeler.