Costumed in the Garden

We’ve long been fans of the tropical crepe ginger, Costus speciosus. We’ve trialed it several times, however, with no long term winter hardiness here in Zone 7b…until…a group of friends were botanizing in far Northern Vietnam, near the Chinese border, when plantsman Ozzie Johnson spotted it growing there at 3,900′ elevation. Returning home with a piece, it was trialed, and discovered to be dramatically more winter hardy that the form that’s commonly grown. With a huge native range from India to Australia, it’s surprising someone hadn’t thought to look for a winter hardy form before now. So far, our 6′ tall specimen, which flowers all summer, has survived 11F, and the same plant at the Atlanta Botanic Garden had no trouble with 5F. The plant has now been named in honor of our friend, Ozzie Johnson, who will now be commemorated by his find as Costus speciosus ‘Wizard of Oz’.

The only thing that remains is to figure out what genus name we should use to list it. 2006 DNA work showed that all Costus species, actually weren’t related closely enough to be in the same genus. Consequently, plants related (same clade) to Costus speciosus were kicked out of the genus Costus, and a new genus was created for them, named Cheilocostus. That wasn’t too bad, until it was pointed out that Costus speciosus already had several earlier names, Banksea speciosa (1783), and Hellenia speciosa, published in 1791. Nomenclatural rules of priority require that the earliest published valid name should always take precedent, which would make it
Banksea. In 2013, however, a paper was published, correcting the name to the earlier, Hellenia speciosa, since the even earlier name, Banksea was ruled invalid because it was too close (parahomonym) to the currently valid plant genus, Banksia. If that wasn’t confusing enough, a 2022 proposal put forth the idea of preserving the 2010 name, Cheilocostus, over the 1791 name, Hellenia, since many species that were earlier attributed to the genus Hellenia, actually turned out to be Alpinias. If you enjoy circuitous puzzles, or peeling onion layers, the field of plant taxonomy is certainly for you.