There ought to be a list of plants named, in with the parcel of up to limit of a dozen plants. Each individual plant should be clearly marked, with the use of an attached label, to identify it...
They aren't actually interested in what cultivar it is ( but you are.) For example, if the parcel contents are all "historic Iris", then " Iris germanica hybrid " ought to be adequate, ( the genus & species names,) noted 12 times,on the paper list of contents, within said parcel..
This exception is mainly for the "home gardener" & not really meant for "Commercial Business" & therefore the exception limit, was set at a dozen plants. Thus, not requiring the Import Permit.