Each photo saved in the ATP Plant Database has a copyright/license category.
If you find a photo in the ATP Plant Database that you want to use, expand it by clicking on it.
Then click on
"More Photo Details"
Look at the row "License".
I don't care who re-uses my photos, so I clicked on a box that seemed to mean "anyone use this freely, but give me credit".
License: Creative Commons (cc-by-3.0) (Attribution)
I forget what the other categories are, but one was "do not re-use" and something else was somewhere in-between.
Here are two I found by spot-checking:
License: All rights reserved
License: Creative Commons (cc-by-nc-3.0) (Attribution, NonCommercial)
If the "License" row says "(Attribution)" or "(Attribution, NonCommercial)", maybe you can just use them without contacting anyone?
@Dave? Can Ps40Life (the original poster) use Plant Database photos that have License = "(Attribution)" or "(Attribution, NonCommercial)" in a garden newsletter for a non-profit group without contacting the photos' owners?