Author: Philip A. Munz

This is my favorite field guide to the vascular plants of southern California. It's out of print, but used copies are usually available at Amazon. It's especially effective if used with the Jepson Manual. Like the Jepson, it requires knowing how to use a key, and familiarity with plant identification terminology. It has no photos, but many line drawings.
The Jepson Manual: Higher Plants of California

First published in 1925, then updated in 1993, the taxonomy is more up to date than in Munz, and it is the standard reference for the vascular plants of California. It has a lot more drawings than the Munz, but is also much heavier, and therefore not quite as suitable as a field guide.
Plant Identification Terminology: An Illustrated Glossary

This has become an indispensable companion to the Munz and Jepson. It is well organized, and every term is illustrated. I've found every unfamiliar term I've encountered in Munz or Jepson.
The Jepson Desert Manual: Vascular Plants of Southeastern California

Published in 2001. This book is based on the Jepson Manual, but even if you already own the Jepson Manual, it is worth getting if you are interested in the flora of California deserts. It is more portable than the Jepson Manual, and has 128 excellent photos.

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