The most comprehensive resource and identification guide to nearly eight thousand varieties of native and naturalized California plants. This thoroughness comes at a cost: the hardcover 1993 edition is over 2 inches think and contains 1424 pages (retails for about US$80). And while the means to identify plants (using key traits and illustrations) is accompanied by special information such as horticultural requirements, endangerment, toxicity, weed status, and notes on the management of sensitive species, it's too heavy and bulky to be used as a pocket manual. However, it has come in useful to members of the California Native Plant Society, who, merely by carrying Jepson manuals with them into the field, have transformed themselves from plant nerds into an elite fighting force. Don't mess with the botanists.

First published in 1925, the Jepson Manual was originally compiled by Willis Linn Jepson. Hundreds of botanists contribute to the modern version. The 1993 edition, edited by James C. Hickman, is published by the University of California Press, ISBN: 0-520-08255-9.