http://garden.org/plants/propo...
It's pretty straight forward, really.
The Primary Common Name field just needs a common name for the plant. In this case, there are several, but either Rose Mallow or Hibiscus will do. Doesn't matter which, other common names can be added later.
The Accepted Botanical Name field would normally include the Genus name followed by the specific epithet, but since this is a hybrid cultivar, it's just the genus name, Hibiscus.
The site you referenced doesn't list a Trade Name or Series Name, so you can ignore that (if we find either later, they are easily added).
The Cultivar field would be Plum Fantasy.
