We've discussed this a few times in the past.
I'm not opposed to having it in the database and I think it could be somewhat useful, but the native plants issue brings along with it invasive plant discussions which brings emotions into the mix. Some people are unable to discuss invasive plants without resorting to emotionally charged arguments and that's bad for a community. Thankfully we have evaded that problem here at ATP and I want it to remain that way.
So, if we do add this into the database, you'd have to know that I'll pull it back out later if it becomes a problem.