Botany in a Day, 6th ed.
Thomas J. Elpel
My go-to reference for identifying plant families. This is the book that got me started on plant identification!
Sagebrush Country: A Wildflower Sanctuary
Ronald J. Taylor
The first book I used to identify wildflowers around our campsite outside of Zion National Park. It was published in 1992, so some plant families and scientific names have since changed, but it’s a great resource.
Wildflowers of the Rocky Mountain Region
Denver Botanic Gardens
One of the first books I used regularly to identify wildflowers.
Plants of the Rocky Mountains
Linda Kershaw, Andy MacKinnon, Jim Pojar
I find the organization to be a little weird, but I love the thumbnails at the beginning of each section, and the dichotomous keys are great.
Zion National Park Common Plants
National Park Service
Very helpful reference for park plants, but it does not include pictures of most of the plants.
Bryce Canyon National Park Wildflowers Web Page
National Park Service
Decent reference for plants in the park because it has pictures of the flowers; however, there are a limited number of plants shown on the site
Plant Identification Terminology: An Illustrated Glossary, 2nd ed.
James G. Harris, Melinda Woolf Harris
Although not a reference for identifying plants, this has been and invaluable resource for understanding the terms in plant descriptions since I am new to botany and plant identification.