Androsace sarmentosa subsp. primuloides ?'Chumbyi'%20in%20trough%20at%20New%20York%20Botanical%20%20Garden%20(Chris%20Chadwell)%20IV.JPG?part=0.4&view=1&vt=ANaJVrHlgpTTxnWxGrnNPeZMUz_vLJGM8HIucL9mc5HgXhx9zRIvEFmScekziNkUkhHmZdqkshYwDs-qY19vXajZ3AaANGCMeTfis-7Lxs2LPkGL1M0-Wws'Chumbyi'%20in%20trough%20at%20New%20York%20Botanical%20%20Garden%20(Chris%20Chadwell)%20II.JPG?part=0.2&view=1&vt=ANaJVrE_p68YkgpQxvrNDm0YdiuxfnQCe3s8AXuvLsCC3ScaD3-22NC79N6BxIdPpbwB2lr6yXgKUhcJ9T3Bp6drugZZQUiskX3vl3mdYdxcth5uLrcc3uc'Chumbyi'%20in%20trough%20at%20New%20York%20Botanical%20%20Garden%20(Chris%20Chadwell)%20III.JPG?part=0.3&view=1&vt=ANaJVrG4h7cxDFTLt-dK3ReSRRXQvLlOSfZLi7gdmXPIs1u_pQMjRPGPP6tOg125tNTXXAuYZVJtjVhRkJAWV9L6jx5YEf_I8_monxwCD0xrQFNy4hRaYtk

Following my posts about Androsaces, I share some images I took of an Androsace labelled as A.studiosorum 'Chumbyi' growing in troughs in the rock garden at New York Botanical Garden.
There is much confusion about the differences between A.sarmentosa and A. studiosorum.
The latter species was previously known as A.primuloides, which at one time I understood was primarily a NW Himalayan species found in Kashmir and Himachal Pradesh whereas A.sarmentosa was primarily an Eastern Himalayan species, typically found in Nepal.  As Chumbi is a district which separates Nepal and Bhutan (the route through which British mountaineering expeditions attempting to climb Mt. Everest from the North (Tibet) - it was first climbed from the south (through Nepal).
If A.studiosorum is not found in Chumbi (after which cultivar 'Chumbyi' is named) then it would have to be Androsace sarmentosa.  However, what a plant is labelled as in cultivation is no guarantee the identification is correct.
I have recently noted that there appear to be no records for Androsace sarmentosa from Chumbyi!
Flora of Bhutan records A.sarmentosa from Tanglu above Darjeeling on banks and paths in forest and alpine meadows @ 2740-3700m.
As to how to distinguish between A.sarmentosa and A.studiosorumFlowers of the Himalaya say the latter species is distinguished by the outer bracts of the umbels being lanceolate (not linear) and with more numerous and longer stolons to 12cm with reddish-brown hairs.
Kletter and Kreichbaum looked into the matter in 'Tibetan Medicinal Plants' but their findings partly contradict those differences given in 'Flowers of the Himalaya'!  They say A.studiosorum it differs from A.sarmentosa on the basis of having leaves with a narrow petiole, broader bracts and inflorescence with villous, white hairs whereas in A.sarmentosa the hairs are brown and wavy (the opposite of what
Polunin & Stainton said).  Oh dear!  I presume the colour of hairs is primarily based on what they appear like in dried, not living specimens?
Kletter & Kreichbaum also say that Nasir says both species overlap in their distribution in the Western Himalayn regions of Kumaon, Tehri-Garwhal, Lahoul, Chamba and parts of W.Nepal, where plants exist which cannot be assigned with certainty to either species. They concluded they could not decide whether specimens collected on Rohtang Pass in HP which species it belonged to, so assigned a name of Androsace aff. sarmentosa.
I have observed what I understand to be what is now called A.studiosorum in both Kashmir & Lahoul.  Plus what I take to be A.sarmentosa in Central Nepal.  I have an "overall" impression of both species but whether that is better than the herbarium botanists have come up with, we shall see?
According to 'Flora of Gangotri NP' most of the specimens in herbaria they consulted which had been named as A.sarmentosa were in fact (on the basis of the colour of hairs it seems) A.studiosorum - yet they state that A.sarmentosa is found in Kashmir and I thought it was not!  I have checked with Stewart and Nasir who also do not list A.sarmentosa in Kashmir - so I suspect the authors of this flora have made a mistake. They follow Nasir in saying hairs in A.studiosorum are white.
Did Polunin & Stainton make a mistake?
Perhaps, most members of this group will emphasise with the observations of Smith & Lowe in 'Androsaces': one of them made a careful comparison of herbarium specimens of the two species, failing to reveal any clear differences!  Though with the caveat that differences did exist but were not such that they would be noticeable to a gardener).
I think what this confusion helps illustrate is that despite a lot of effort, sometimes one just cannot decide which species a plant belongs to with certainty.  Having been involved with identifying plants for more than 40 years now, I can state that I frequently meet people form all sorts of backgrounds who EXPECT this can easily be done.  They do not appreciate how variable species can be and we CANNOT always neatly "pigeon-hole" a specimen into this particular species (or genus or family), subspecies or variety nor should we always expect to - however unsatisfactory that may be.
Better to adopt a cautious approach to identifying plants - often a degree of uncertainty exists.
It is important for members suggesting identifications say WHY more often, so this thinking/reasoning can be checked - in this
way we learn more and the overall level and reliability of identifications improve, which they do need to.