Plant Images & Clipart

Plant Images

Calphotos: Plants
https://calphotos.berkeley.edu/flora/
Database of 116,00 plant images, searchable by color, location, name, and photographer. Most photos are available for non-profit use. See usage and permissions page
elib.cs.berkeley.edu/photos/use.html for more information. 

Henriette's Herbal 
www.henriettes-herb.com
16,000 images:
www.henriettesherbal.com/pictures/index.html#fine-print

USDA Plants Gallery
https://plants.usda.gov/gallery.html
Most information presented on the USDA Web site is considered public domain information. Public domain information may be freely distributed or copied, but use of appropriate byline/photo/image credits is requested. Attribution may be cited as follows: "U.S. Department of Agriculture."
Some materials on the USDA Web site are protected by copyright, trademark, or patent. These materials should be clearly marked and permission must be obtained for use beyond personal use.

Pixabay
https://pixabay.com/
Royalty and copyright free images that have been placed in the public domain.  Credit to the creator of the image is suggested. There are some images that are available only for purchase. They are clearly marked.

Wikimedia Commons
https://commons.wikimedia.org/wiki/Main_Page
Many images are in the public domain. Read licensing information for each image.