Alpine Salix ID

[Lori S.]

I hope no one minds if the inaugural posting to the NARGS Plant Identification is a challenging one!  (Or so it is to me, at any rate!)
This is a high alpine Salix, seen in northern Banff National Park (eastern slope Rockies) at approximately 2600m elevation in mid-August.  The leaves are very tiny, approximately 4mm, to 8mm maximum, in length.  (The ring in the photo is 16mm in diameter, for scale.)
I'm intensely curious as to what this might be!  (I thought Salix vestita, possibly???)
Thank you in advance for any insight,
Lori

[Booker]

A magnificent dwarf Salix, Lori ... I'm afraid I can't assist with a name for you but it looks even tighter and prettier than Cotoneaster microphyllus.

[Hoy]

Have you considered Salix nivalis?

[Lori S.]

Hi, Hoy.  Thank you for the suggestion. 
Flora of Alberta (Moss & Packer) refers to one of the subspecies of S. reticulata that occurs in our area as
Salix reticulata spp. nivalis.  Is that likely to be the same species to which you refer?  (Assuming it is the same, it seems it has been elevated to a full species, since the publication of my reference.  It's hard to keep up!)
If so, yes, "Salix reticulata" and Salix vestita seemed to be the likely candidates.  If we get up to that area again next summer, I'll try to locate the plants and look at the undersides of the leaves.  Perhaps that will help?

[Hoy]

Hi
I have no special knowledge of Salix, and certainly not from North America. I just have an old copy of "Rocky Mountain Wild Flowers" of A. E. Porsild (1974) with drawings of Dagny Tande Lid. It covers Jasper, Banff and Waterton Lakes National Parks. The book mentions that it is about 35 species of Salix in the area, but only 5 are pictured. The "Snow Willow" (Salix nivalis Hook. (endemic to the area) looks very similar to your picture. S. vestita has more net-veined leaves (as far as I can see from your picture). I know S. reticulata well from Norway, and it has bigger, very reticulated leaves (at least here).

[Lori S.]

Ah, yes, Moss & Packer indicate that S. nivalis Hook. is synonymous with what they call S. reticulata ssp. nivalis Love.  Thank you for the additional information!  
I have that reference also and I've just read that it says Salix nivalis is "the smallest of the willows and perhaps the smallest woody species in the area"; "tiny, oval-roundish leaves, often less than 0.5cm long".  That would make it a very good possibility.
Moss & Packer also say the leaves are from 0.4 cm (with an implication that this is less common), more commonly 0.8 /to 2 cm long.