The Black Mountain (Bhutan) - Primulas and Problems

Jigme Singye Wangchuck National Park covers 1,730 sq kms in south-central Bhutan and contained within the park is Durshingla, the Black Mountain. (JSWNP Facebook page)

Durshingla © Darlo Letro

In 1915, Roland Edgar Cooper made the first botanical expedition to Durshingla, which he called Joedawnchi. From Cooper's 1914 and 1915 Bhutan expeditions, 19 species of Primula were described though only six are now considered to be distinct species: P. chasmophila, P. eburnea, P. erythrocarpa, P. strumosa, P. umbratilis and P. xanthopa. He wrote about those trips and specifically about the Primulas he found in Notes of the Royal Botanic Garden Edinburgh, Vol.18, Nov. 1933.

Ludlow and Sherriff (L&S) visited Bhutan several times and Sherriff's 1937 expedition was specifically to Durshingla which he called Dungshinggang. He found no new Primula species there but he was able to recollect known species.


Sherriff's route up Durshingla in 1937

Both expeditions used a route from Chendebi, travelling west over the Lamse La into the Phobjikha valley. From there they ascended the ridge over the Byasu La to Chapepusa and then followed the ridge east until it met the main N-S ridge leading to the peak.

Primulas & Problems

1. The most interesting species found on Durshingla is Primula chasmophila and, so far, it is only found on this mountain. Cooper first discovered it in September and his herbarium specimen was sparse, so it was described from cultivated plants grown from seed. Sherriff collected it on the mountain ridge near the Nabzi La. Though it was scarcely in flower, he noted its deep, rich blue violet color, red eye and its cliff ledge habitat and compared it with Primula umbratilis, a much more widespread species that is also found on the mountain (Cooper 4822). What to photograph if you see this species? Variations in flower color, details of the hairs on the flower scape, leaf study.

Primula chasmophila L&S 3301,
courtesy Royal Botanic Garden Edinburgh

2. The type of Primula hopeana was collected by Cooper on Durshingla, in September, so the plants were in seed. In the description it was noted that sometimes the tube of the flower was "pink", which was seen by Sherriff on the mountain and is seen in populations in Arunachal Pradesh. This species resembles Primula sikkimensis and is sometimes considered a variety of it. Species in the Sikkimensis Section hybridize in the wild and it is very difficult to sort some populations into species. Sherriff noted that he saw true (yellow) sikkimensis here also, so I would expect some hybridizing. What to photograph if you see this species? Leaf study with the corresponding flower color and flower shape. Variations in flower color (don't forget to also show the flower face).

Primula hopeana

3. On the ridge to the NW of the Lamse La and also on the lower ridge of Durshingla Sherriff found a plant he thought was Primula strumosa but was later found to be Primula elongata. Primula elongata, P. barnardoana, P. sikkimensis and P. strumosa are all yellow flowered, so you must look to other characteristics to distinguish between these species. In Bhutan two variations of P. elongata occur, having slightly different leaves. What to photograph if you see this species? The most important image is a leaf study! The flower tube is also important to determine this species (side of the flower).

Primula elongata

4. On the high hills and passes surrounding the Pobsikha valley and lower on the ridge of Durshingla grows Primula whitei. The type location for this species is the nearby Pele La. This is another problem species as it is close to or the same as Primula bhutanica. See this blog post for details. What to photograph if you see this species? Any population of P. whitei should be checked to see if plants have any characteristics of P. bhutanica in particular the calyx (side of the flower). A leaf study, especially of the older leaves, would be useful.

Characteristics of P. bhutanica. Can you find plants like these in a population of P. whitei?

5. Another species in the Petiolares section was found growing in this area (Lamse la, Lao La). It caused Sherriff a lot of confusion as he thought it might be P. boothii, but it was later identified as Primula bracteosa. The Flora of Bhutan has P. boothii as a synonym of P. bracteosa, but there is a distinction between the two in that P. bracteosa develops leafy bracts among the inflorescence as it goes into fruit. In flower, the two species are indistinguishable though it is said that P. boothii does not have farina and has a slightly different calyx. What to photograph if you see this species? It is best if the same plants can be visited in flower and in fruit. The calyx detail and any farina should be photographed. A leaf study of the plants in flower and in fruit, including the later leaves in the inflorescence is necessary.

Primula bracteosa,
courtesy Royal Botanic Garden Edinburgh

6. The first Primula encountered by Sherriff on the way to Durshingla was Primula flagellaris, which he found within a mile of Chendebi, on the right side just before cliffs, on the way to the Lamse La. This has been a problem species because it has also been considered a variety of Primula tenella. The distinctions between P. tenella and P. flagellaris are in the flower size and color, number of flowers per scape (1 or 2), presence or absence of bracts and presence or absence of stolons. I believe the species described in 2004 as Primula rebeccae is a synonym of Primula tenella. What to photograph if you see this species? Both a flower study to show size and color variation and a leaf study (both surfaces) with measurements would be helpful. Images of the stolons (runners) and the new plantlets that form on the ends of the stolons. Flower stalks should be checked for bracts (which look like a tiny leaf) and photographed if found. Sherriff believed there was an altitudinal difference between the two species, with P. flagellaris at a lower altitude than P. tenella. It would be exciting if P. tenella was found at higher elevations on Durshingla.

Primula tenella usually has 1 flower and a bract.

If you are at Chendebi, look for a small species on the near by hills (SW) for Primula erythrocarpa which looks like P. atrodentata or a small P. denticulata. Check for basal scales under the leaves and show the hairs on the leaves.

Other Primula species found on Durshingla: P. atrodentata, P. munroi, P. calderiana, P. megalocarpa, P. waddelli, P. bellidifolia, P. obliqua, and P. glabra.

I am uncertain of the exact location of Nabzi La on Durshingla. If you have the GPS coordinates for it or a GPS track for the route up the ridge, please contact Pam. If you are interested in more details of these species or locations, or if you have images of these species, please contact Pam.

A video of Foresters in Bhutan https://leythro-darlo.blogspot.ca/2017/02/conservation-journey-video.html

Pam Eveleigh © 2017