Gossip Articles

The search for true Hosta sieboldiana

By Bob Solberg

     I now give an everchanging lecture entitled “Travels with Bob”. I like to put you in the vacant front seat of my old truck and just go where we go, see what we see, and talk hostas and whatever else we run across. Frequently it is visits to hosta hybridizers and photos of hostas without names that may or may not ever see the rooting jars of a tissue culture lab. Sometimes it is hosta conventions displaying perfectly grown clumps of rare hostas that I have never seen.
This time it is a trip to Japan to see hostas in the wild!
     Now before we get started, just a short aside. How do you feel about spending an evening with friends just back from a visit to Tuscany when suddenly they ask, “Would you like to see our photos of the trip?” I will pause while your emotions subside…
     Before digital cameras this usually meant removing a photo album from the end table drawer and slowing looking at each photo with appropriate commentary. Today, it means hours of HD pics on the big screen TV and a short nap.
     Without the limitation and expense of film, every detail of every trip is recorded in at least triplicate. And so, it was on our Japan trip. Between Mark Zilis, his son Andy, and myself we took maybe 4500 photos, not to mention the 15-minute video Mark took as we climbed a very narrow winding road in our rental car along a raging river to the top of a mountain to see H. kikutii var. kikutii in the pouring rain. We photographed strange animal crossing road signs, little
trucks, tunnels, roof tiles, you get the idea. Why not, the film is free.
     Personally, I have yet to see all of Mark’s photos and I went on the trip. I’m sure you would be satisfied seeing just a couple of the wonderful photos of the probably 500 he took of the vine Campsis grandiflora in full bloom. Me too, but remember I saw all this live and in person. The point of this aside is that I realize reliving where you have been, slowing down the time that flew by so quickly with photos when you return, is much more interesting for the traveler than his guest. A little goes a long way. To that end I will not share with you the French fry tale that became a reoccurring joke for the rest of the trip.
     So, let’s go to Japan. This was not just a sightseeing adventure for me, it was a scientific mission, a quest for the Holy Grail of hostas Hosta sieboldiana. As I wrote in my article in the last issue of The Hosta Journal:
    “The focus (of the trip) was on Japan’s largest hostas, all closely related species, H. montana, H. sieboldiana, and H. fluctuans. We also saw H. sieboldiana glabra at the northernmost end of its range.
     That said, there were several questions that all of Hostadom would like answered about these hosta species and their relationship. In recent times there has been some question as to whether these are really separate species or maybe all forms of one big species that is still in the
process of evolving. In addition, even the actual existence in the wild of what we call H. sieboldiana and to a lesser extent, H. fluctuans has been doubted. We wanted to learn what Japanese collectors thought about their existence. I have always felt the best way to attack these questions was with boots on the ground. Herbarium specimens tell one side of the story but seeing hostas at home is believing.
     My goal was threefold. First, I wanted to study the relationship between these three species and to a lesser extent, H. sieboldiana var. glabra. Are they biologically isolated or do they freely hybridize? Second, to see the plant the Japanese refer to as To Giboshi. And finally,

to see if there are hostas in Japan that look like the European plants named H. sieboldiana. Is the H. sieboldiana we know in our mind’s eye found in the wild?”
     To make a long story short, yes, we did find true Hosta sieboldiana in the wild, at least one large clump that looked all the world just like the ones in Europe and in our gardens. We saw H. montana, H. fluctuans and H. sieboldiana var. glabra in different habitats in northwestern Honshu. Six months removed from then and having spent my winter reading about the speciation of Darwin’s finches and the 40-year study of Peter and Rosemary Grant, I wonder how all this came to be. Huge hostas on rocks similar but different enough to have separate names in
Japanese and Latin.
     Based on the work of N. Fugita in the 1970’s in Japan this group of “species” are all lumped into a single species, called H. sieboldiana, because of the group it is the oldest name. Our guide and now my friend Hiroshi Abe believes like most Japanese that they are all populations of one very large species that virtually extends the entire length and width of Japan. Their Japanese names, H. montana is Oba Giboshi, the “large-leafed hosta”, H. sieboldiana is To Giboshi, “hosta of old”, and H. fluctuans is Kuronami Giboshi, “dark, wavy hosta” are still used to distinguish the differences in those hostas.
     Let’s just close our eyes and think of it happening this way. First there was Oba Giboshi, a widespread hosta that colonized the islands of Japan. As time went by different populations of this single species began to become different along the edges of its range as they adapted to local
habitats and became biologically isolated in different river valleys. Their gene pools became different enough that we could see them as different hostas, phenotypically different, having distinct characteristics, so we gave them separate names, To Giboshi and Kuronami Giboshi.
     We have all heard of Charles Darwin theory of survival of the fittest, the driving force behind the evolution of plants and animals. The question that puzzled him most was the origin of species. In our case, why are there 40 something hosta species in the wild and how did they arise. Darwin’s idea is that all speciation, the formation of new species, follows the pattern of a tree. The first hosta to appear, (we think this happened by the chance crossing of two different ancient plant species in nature, because of the very high chromosome number in hostas), then “branched” out to become many different species as it spread to new islands and habitats. Adaption or specialization to their new homes created different plant sizes, bloom times, leaf shapes and many other processes unseen within the plants.
     It is thought that this process of speciation is currently continuing today in Japan and in hundreds or thousands of years maybe H. montana and H. sieboldiana will be very distinct. And then maybe not. What we have learned from Darwin’s finches is that sometimes distinct populations genetically drift back toward each other and even fuse into a single species again. Then if environmental conditions change, they may start to drift apart again. In other words, speciation, evolution, is an ongoing process driven by adaption to changes in habitat. We have also seen that these changes can occur, at least with finches in tens of years not thousands.
     Now I wonder, is this group of hostas steadily moving apart from each other, continually becoming more distinct with each new yearly crop of seeds or are the moving back closer together, looking more like each other every year in response to habitats becoming more similar in those river valleys instead of different. Large storms with intense rain will wash these hostas from their rocky perches allowing for a rapid turnover in the population which is recreated from the few remaining individuals. Change can be radical. If you believe that the climate is changing and now storms are more intense then you might deduce that hosta speciation might diverge or fuse at a faster pace now and in the future.

     Darwin’s theory of adaption is well known and accepted generally by most who study evolutionary biology and can be demonstrated by species on islands like Darwin’s finches readily in real time. His second theory that drives speciation is less widely held. It is that “beauty”, Darwin’s term, may also be a powerful force that selects for certain decorative genes that may not provide increase adaption to habitats or increase fitness. Think of a peacock’s tail. Female peacocks are attracted to the pattern of the tail, how it is displayed and the mating dance.
The female drives this selection part of evolution. It is sexual. (Remember male birds are usually the most decorated of the species not females.) This may or may not be driven by fitness.
     Hostas do not have separate sexes, both are found in every hosta flower, so sexual attraction between hostas probably does not exist, but it might with their pollinators, the bees. It is thought that H. plantaginea is the hosta nearest the base of the trunk on Darwin’s evolutionary tree. It also has the most different flowers of any hosta species. Their fragrant flowers are unique to hostas, the flowers are very large, and they are white without stripes, and open at night. They are designed to attract, not bees that pollinate during the day but moths that appear at night. Their attraction is fragrance and a big shiny, white target.
     As hostas moved from the Asian continent to the peninsula of Korea and down to the islands of Japan, (and out the branches of Darwin’s tree) somewhere along the way they became bee pollinated. Maybe moths were not present in these new lands, maybe there were lots of bees nosing around all the time. Hosta flowers evolved to be bee size, with purple stripes to attract them and opened during the day. This change was so successful that all hosta flowers became sexually attractive to bees only and the flowers no longer needed to produce the oils that produce fragrance saving that genetic cost, a production cost.
     This savings of energy by not producing fragrant oils and the change to new pollinators, most evolutionary biologists would see this as adaptive change. These hosta are fitter, in that in theory, they produce more seeds and do it at a lower cost. They are more efficient. But maybe the bees just like purple striped flowers and think they are pretty.
     Hosta flowers do vary within a species in the wild. Not all are light lavender with darker stripes. Some are darker purple, some have extra petals, some have no stripes. Some are even different colors, green, yellow or even brown. These mutations are rare and usually deleterious, not advantageous. But who decides this? Not the hostas themselves, but the bees. It is sexual selection, certainly in this case.
     As a hosta hybridizer, these flower mutations excite me. Even if the bees are not, I am attracted to them. I would like to see hostas with as many different and colorful forms of flowers as have been hybridized in daylilies from just a few yellow and orange forms. This too is selecting for “beauty” in the form of human selection. I have taken on the role of the bee pollinator and select seedlings that will able to reproduce the new flower colors I desire. The hostas are no longer selected for fitness first, how well they grow, but for the flowers alone. Think of the yellow-flowered ‘Miracle Lemony’ as an example of a less fit hosta that is selected for beauty.
     So, back to the question at hand. Are H. montana, H. sieboldiana, and H. fluctuans separate species at this point in time or are they still one large variable species in the process of fusing or diverging? It is hard to say. They do have traits that differentiate them from each other.
H. montana has its typical star arrangement of bracts on its inflorescence, H. sieboldiana has a high number of vein pairs, 16-18 as opposed to 12-13 pairs to H. montana, and H fluctuans has a more upright habit than H. montana with straighter scapes that also lack the star arrangement of