It's pretty easy to remove your own photos from the database. Just click on the picture in question, scroll to the bottom of the page and click the "Propose this image be deleted" link and then click the "Submit the proposal" button.
https://garden.org/plants/prop...
As long as you are proposing to delete YOUR OWN photo I will approve the proposal as soon as I see it, no explanation needed.
Members own the rights to their pictures, even after they have been submitted to the database. They can remove them anytime they want for any reason they might have, or even no reason at all.
Now, if you try to delete someone else's photo, that's a different story. We need a very good reason (clearly incorrect ID most often) if you want to mess with another person's photos.