Cordyline has been in the database for a long time:
Ti (Cordyline)
The plural of genus, by the way, is genera, not genuses.
The parent plant for Plectranthus applies only to Plectranthus scutellarioides and its synonym, Solenostemon scutellarioides, and it actually is the parent plant for the Coleus Database.
Coleus (Coleus scutellarioides)
We really do need a general Plectranthus entry for the other species, I agree. Evan might be able to edit the Coleus Database parent plant so that it doesn't show up just as Plectranthus. I'm not sure of the mechanics for this change.