The result seems to be my earlier confusion of what the plants tag was supposed to be for, in which new users just pick the first tag they can think of, in this case a generic plants tag.
My thought is that maybe we don't need to organize identification requests like this. Does it really matter if an identification request is about a plant, or an insect, or anything else for that matter? Perhaps all that really matters is that it's an identification request. Both the question title and body should describe what's being asked about identifying.
That way, we can burninate the plants tag, and in the worst case scenario where a new user doesn't know what to use for a tag, they'll just pick a random tag and it will be obvious that it will need to be fixed.
Another option could maybe be combining the terms, and making two identification tags. One for plant-identification and one for animal-identification. That way typing in plant would show that option in the list.