Thomas,
Could you please clarify what you are after when you say "plant keys"? It sounds like you are talking about the plant callouts. If this is the case, your verify labels will update anything that may have changed in your drawing. Also, using the group label tool will allow you to redefine or reposition the callout to a certain area. Please see the link below for more on these items. If I have misunderstood what you are after, please let us know and we can go from there.
Updating Plant Label Quantities