At least a couple classes are visiting arboretums, gardens, and malls and photographing lots of plants. Nearly all are cultivated and aren’t marked as such. I’ve gone through many to mark them cultivated (and sometimes identify) but there are hundreds. If some of you would be willing to check more, that would be useful. Identifications are simpler than they might be because some of the plants are labeled and because multiple people photo some of the same individual plants.
EDIT: Wait a week or two before fixing things. The massive project includes a planned time to “clean up” observations. See below.