Oak apples, honeydew and ambrosia galls, witches’ brooms, and fasciations—all are types of plant galls, a commonly observed, yet little-understood botanical phenomenon. Often beautiful and bizarre, galls are growths of various shapes, sizes, and colors produced by host plants in response to invading organisms. This guide, a trove of natural history lore, explores this hidden realm, taking a fascinating look at the world of plant galls, the organisms that initiate them, their host plants, and their intricate behaviors. Focusing on native trees and shrubs, but also discussing several galls that occur on herbaceous and ornamental plants, it illuminates the complex interrelationship between botany and entomology and magnifies our awareness of plant communities in the West.

* Identifies more than 300 species of galls—95 on oaks, 22 on members of the rose family, 60 desert species, and 35 species that are new to science

* Describes plant galls from coastal dunes, the high Sierra, the Great Basin, forests throughout the western states, and the Mojave and Sonoran deserts

* Includes information on host selection, growth and development, predator and parasite defense, and animal and human uses of galls

Ron Russo recently retired as Chief Naturalist with the East Bay Regional Park District in Oakland, California. Among his books are Hawaiian Reefs: A Natural History Guide, Pacific Coast Mammals, Mountain State Mammals, Pacific Coast Fish, and Pacific Intertidal Life.

"This exciting book belongs on every naturalist's bookshelf. The excellent color photos and clear text will endear it to the amateur while the accurate identifications will please the professional. This book is an ideal gift for anyone who enjoys spending time outdoors."—Katherine Schick, Essig Museum of Entomology, University of California, Berkeley

"This identification guide, with its summaries of the science and lore of galls and their causative organisms, engagingly draws one into another barely explored world, one presently known only to a few. With the publication of this book, many more can now appreciate these fascinating plant growths."—Raymond J. Gagné, Systematic Entomology Laboratory, USDA

"This comprehensive, descriptive, and beautifully illustrated guide to plant galls of the West will appeal to both professional and amateur."—Diane M. Erwin, Museum of Paleontology, University of California, Berkeley

"A great book for entomologists, plant pathologists, and would-be naturalists who are curious about the amazing insect-plant relationships illustrated by plant galls."—Charles Dailey, Sierra College

Read Ron Russo's article "Confessions of a Gall Hunter", in Natural History Magazine