Back in the early 2000s, we grew the spiral ginger, Costus speciosus for many years, before finally loosing it in a very cold winter, but its potential hardiness has always fascinated us. In 2013, Georgia plantsman Ozzie Johnson collected a specimen near the border of North Vietnam and Southern China at 3,900′ elevation. Below is Ozzie’s collection this week at JLBG, after our recent winter of 11 degrees F. The same plant, growing in Atlanta, survived 5 degrees F this winter without protection, so I think we can safely say we have a Zone 7b hardy form. This exceptional clone has been named Costus speciosus ‘Wizard of Oz’. It will take a few years to build up stock, but we’ll get this one ready as fast as possible.
Good morning JLBG. How timely is this post as I give a tour of my garden this morning to a group of visiting botanical friends from Vietnam forestry who work with our group’s effort to study the plants of Vietnam such as this collection of Costus. It’s in full flower.
Fantastic…great connections yield great plants!
A few years back, Costus speciosus had been reclassified to Cheilocostus speciosus.
Great point. When we have plants that are in the midst of a taxonomic tug of war, we prefer to hold off on making name changes, so we don’t add to the confusion by changing names back and forth. Indeed, Costus taxonomy has been in a state of flux for several decades. First, the genus was moved from the Zingiberaceae family into its own family, Costaceae. Then DNA showed that the genus Costus was actually comprised of several different genera, with three main evolutionary groups, one in the Americas, one in Africa, and one in Asia. Due to early DNA work, many of the Asian plants, including Costus speciosus, were moved into the genus Cheilocostus. Unfortunately, it was determined afterwards that there was actually an early published name (Hellenia) from 1791 that took priority, so our plant became Hellenia speciosa. Further sampling within the Hellenia group found it to be polyphyletic. In other words, the genus didn’t just contain brothers and sisters, but it had a bunch of distant cousins, who needed to be kicked out. In the world of taxonomy, this kind of non-sibling fraternization is a no-no. A 2022 DNA study showed that some of these members of the genus Hellenia actually belong to a new genus, Parahellenia. Fortunately, our plant, Hellenia speciosa was allowed to remain in the genus Hellenia. There is a complete phylogeny for the family Costaceae scheduled shortly, and we hope to avoid another genus change for the plant formerly known as Costus speciosus.