Botany in a Day by Thomas J. Elpel is a popular plant identification guide that teaches the "patterns method," focusing on recognizing plant families rather than individual species. It helps users quickly identify thousands of plants by learning the common characteristics and uses of major plant families, making it a valuable took for herbalists, naturalists, and students. The book is used as a textbook in many schools and is praised for its practical, pattern-based approach to learning about edible and medicinal plants.