The Truth about the Blue Nivalids (P. youngeriana)

Of the Blue Nivalids, this perhaps one of the easiest species to write about. That is because it is little known, probably only collected once ever, by Sherriff and Taylor (PDF) , on the Mira La, Tibet in 1938. A search of the Chinese Virtual Herbarium turns up no Chinese collections and that could be because to get to the Mira La is a two day hike and suitable elevation isn't accessible via road in that area. Above is the holotype from the British Museum (specimen BM00099651).
Mira La, Tibet (Namcha Barwa Peak in the right background)
The Mira la is a pass of 15,800 ft (slightly higher on Google Earth), NW of Tsela Dzong (on the Tsangpo river) and SW of Bayi (Nyingchi on Google Earth). The area is drier than surrounding valleys and mountains, is less forested, and screes predominate, though many high alpine lakes dot the landscape including a small one at the foot of the pass on the south side.
Primula littledalei (under boulder to right) habitat similar to P. youngeriana
Primula littledalei, Mi La, Tibet
In the original description, the species is compared with Primula obtusifolia, another nivalid but from the NW Himalaya. The habitat where P. youngeriana was found - growing under huge boulders in dry moss, is strongly similar to that of P. obtusifolia but also to P. littledalei which was growing in abundance on the Mira La too. Sherriff mistakenly thought P. littledalei was P. rotundifolia which has similar orbicular leaves. P. obtusifolia has oblong leaves like P. youngeriana.

Sherriff thought that P. youngeriana was an unusual form of Primula macrophylla var. macrocarpa (now P. megalocarpa) but with flaccid leaves and copious white farina, not something new. What makes P. youngeriana so distinctive is that the bracts are long, linear and acute at the tip and the calyx is large (1-1.5cm) and cut to the base into lanceolate, patent (spreading) lobes which are acute and densely farinose inside. P. megalocarpa also has calyces which are cut to the base but that species differs in other characteristics.
A portion of E00024585
courtesy of the Royal Botanic Garden Edinburgh

The flowers of P. youngeriana are deep blue-violet, sometimes lilac, with a white eye and the corolla lobes are entire. See P. littledalei, P. rotundifolia, P. obtusifolia and P. megalocarpa in the Species Gallery. 
This post is one in a series about Chinese blue nivalids. See the introduction post.


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