This image has a creative commons license as well as a remark "This image is not copyrighted and may be freely used for any purpose." If the image is really not copyrighted, it's illegal to slap a cc license on it.
This image is not copyrighted and may be freely used for any purpose. Please credit the artist, original publication if applicable, and the USDA-NRCS PLANTS Database. The following format is suggested and will be appreciated: