We have many users that rely on common names and they often select the wrong taxon when this occurs.
For instance:
California buckwheat, Eriogonum fasciculatum
California buckwheat, Eriogonum fasciculatum fasciculatum
I would recommend removing common names from most subspecies, as they should only be selected by users that read the scientific names. The only case where a subspecies deserves a common name is when that taxon is well recognized, obviously different, or is unlikely to be confused. For instance, the yellow-rumped warbler, as follows:
Yellow-rumped warbler, Setophaga coronata
Myrtle warbler, Setophaga coronata coronata
Audubon's warbler, Setophaga coronata auduboni
In the case of the plant, there is not really a reason to give the subspecies a common name, not even "nominate California buckwheat", in my opinion. I think I started the "nominate" trend so that may be my fault, but looking back I don't think I agree they (plants in this case) need names.