If you click on "edit data details" on the page for any entry in the database, you'll see a form showing the types of information required.
http://garden.org/plants/propo...
If there is enough information that applies to every single Ziziphus, Dave can turn the genus entry into a parent plant and add that information to every Ziziphus in the database, but it really isn't necessary to have a "parent plant" for every genus.
As for the lack of documentation, that could be a problem as far as our database is concerned. We usually wouldn't add undocumented cultivars to the database unless the cultivar names were accepted by several sources. Typically, people tend to spell the name of an undocumented cultivar in several different ways and may apply the same name to several different plants.
