Cypripedium tibeticum v. amesianum, a mysterious self pollinating slipper orchid

In the mountains of western Sichuan, China there exists a curious dwarf form of Cypripedium tibeticum with self pollinating flowers. For years this plant has been shrouded in mystery, initially being given the name C. amesianum, and more recently has been assigned to at least two different accepted species, C. yunnanense and C. ludlowii, by two different authors. Hopefully, I can shed light on this diminutive little plant – what makes it distinct and perhaps even delineating its logical position within the known species of the region. It should be noted that there is no clear name for this plant at the moment, nevertheless I will refer to it as C. tibeticum v. amesianum.

This plant is an herbaceous terrestrial deciduous orchid of sparse woodlands and shrub thickets in high mountains. The plant’s habit is very similar to the more typical forms of C. tibeticum except in stature – often standing no more than 20 cm tall. Beyond that, its most salient feature are the flowers, which are borne one to a stem, and rarely exceed 4-5 cm in natural spread. Their color is fairly normal for a yellow based flower of C. tibeticum, with the lip evenly suffused with a wine red color and striated sepals and petals with a similar hue. The lip tends to be a bit more round than most C. tibeticum, rather than laterally compressed. The lip orifice is lightly toothed as well.

Other than size their most distinctive feature is that the flowers are obligate self pollinators. The reason is easily seen when looking at the pollinia which grow directly onto the stigmatic surface of the column. The result is 100% of the flowers forming pods, though of course not all necessarily come to full term.

It appears that this odd little plant is confined to the Hengduan Mountains of western Sichuan Province, and adjacent areas of extreme northeastern Yunnan at elevations between 3000-3500 meters. Here it is found growing in open woodlands, shrub thickets, scree slopes, and travertine formations throughout the region often alongside other Cyps including C. bardolphianum, C. calcicola, C. farreri, C. flavum, C. guttatum, C. shanxiense, and C. tibeticum v. tibeticum. When vigorous it can form large clumps, but also grows singly.

The existence of v. amesianum has been known for nearly a 100 years. It was first described as Cypripedium amesianum by Rudolf Schlechter in 1919 based on material from two collections made by another famous plant collector of the time, Ernest Henry Wilson, in the vicinity of Wenchuan in Sichuan. Since then plants fitting this type have been found throughout the high mountain valleys of western Sichuan and just over the border in neighboring Yunnan.

Unfortunately, the confusion surrounding its taxonomic status has had a more sorted history. After looking at the AMES herbarium specimen, Phillip Cribb (1998) considered it conspecific with C. yunnanense, another diminutive species with C. tibeticum like flowers from the same general region. Then in 2009 Wolfgang Eccarius published it under the name C. tibeticum ssp. ludlowii, thus reassigning the accepted species C. ludlowii, to this varietal status.

To date the plant’s identity remains in flux. Holger Perner (pers. comm.) feels this plant is distinct and deserves at least varietal status under C. tibeticum. He bases this on the consistency of this variety’s self pollinating flowers, dwarf stature, and its natural range. C. yunnanense is not known from any part of northern Sichuan where the type material of C. amesianum was collected and so considering this plant conspecific with C. yunnanense seems unlikely.

Moreover, their flowers only have a passing resemblance of each other. C. yunnanense tends to have lighter pink-purple flowers, more narrow sepals and petals, a white rim around the lip orifice, and a signature white staminode suffused with pink-purple spotting. Also, no known self pollinating plants of C. yunnanense have ever been found. Anyone who has seen them side by side easily can discern these two plants are distinct.

Both Perner and Cribb agree that this plant is clearly not representative of C. ludlowii, which also remains a distinct, yet rather mysterious taxon of southeast Tibet. How Eccarius determined that v. amesianum fits C. ludlowii is uncertain except that in 2007 a small colony of albinistic flowered plants of v. amesianum were found alongside normal colored forms in northwestern Sichuan during a botanical tour. The plants were photographed extensively (but later mysteriously were all collected!). Since C. ludlowii is reported to have yellow-white flowers, perhaps that is where the connection was made. Regardless, since the description of C. ludlowii wasn’t published until 1997 (Cribb), even if these plants were conspecific, the name C. amesianum would take precedence due to the earlier published date. Very likely though, there is no connection between the four type specimens from Xizang (Tibet) that form the basis of C. ludlowii, and the plants Perner calls C. tibeticum v. amesianum. Word is that Cribb has decided to reconsider his position on putting v. amesianum under the species concept of C. yunnanense (Perner, pers. comm.). I’ll keep you posted on any updates about its taxonomic status.

It should be mentioned that this plant is easily confused with C. calcicola since they can closely resemble each other and are often found in mixed colonies in northern Sichuan. The truth is that C. tibeticum in all its forms, along with C. calicola, C. franchetii, C. froschii, and perhaps even C. yunnanense can be difficult to delineate clearly, and often times intermediate forms exist. I saw firsthand a colony of C. tibeticum, C. calcicola, and C. tibeticum v. amesianum that were at times so difficult to segregate that one couldn’t help but think the logical conclusion – this was a hybrid swarm. Perhaps in the future taxonomists will create one superspecies of all of these, possibly under the name C. tibeticum, or maybe even under the more widespread species, C. macranthos.

Taxonomy aside, this is one cool little plant. I was fortunate enough to see it in flower at two distant sites in northern Sichuan in June 2013. It grew in sparse coniferous forest among travertine limestone formations at one site and in a lightly forested limestone scree field at another. Both were high elevation, 3,400 and 3,200 meters, respectively. What a great little plant! As you can see in the photo to the right, its tiny flower easily cradles between two of my not so large fingers. Despite being self pollinating, the flowers must last at least a week before fading.

I also saw flowering plants of both the normal form and the albinistic flowered one at the nursery of Hengduan Mountains Biotechnology, Ltd. in Huanglong (Holger and Wenqing Perner’s business). Here it grew right alongside other forms of C. tibeticum as well as C. yunnanense, making it very easy to see the obvious difference between these plants. Holger managed to salvage a few of the albinistic flowered plants before the colony was totally stripped by plant collectors. Currently he has three adult plants at the nursery. The fate of the others is not known, at least not publicly. Hopefully Holger can propagate this plant in the future since no other albinistic plants have been found in the wild to date.

It appears that this plant is no more difficult to cultivate than the more common forms of C. tibeticum. It requires bright light, even enduring sunshine in cooler climates. A nearly purely inorganic substrate is probably safest in growing them with a pH near neutral. In the winter months particular attention must be given to keep their roots just moist, therefore winter rain and snow can lead to rot and should be avoided. Given the small stature of this variety it probably would make a great potted specimen, too. To my knowledge few have made it into the horticultural trade however – no doubt wild collected material misidentified as C. yunnanense. It is probably optimally grown in USDA cold hardiness zones 4-6.

Is this curiosity a species onto itself, or just a variety of the highly variable C. tibeticum? In time botanists may sort out that question, but for now we can still enjoy this delightful little slipper orchid for what it is – another unique Cyp from the mountains of southwestern China.