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''Salix arbuscula'', the mountain willow, is a low, much branched shrub (to 0.7 metres) having a limited distribution in Northern Europe, occurring from north Scandinavia eastwards to Siberia. In 
As described in Stace''New Flora of the British Isles'';
Scotland
Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
it can be found on damp rocky mountain slopes and ledges, generally at altitudes above 600 metres, rarely outside Perthshire and Argyll.Willows and Poplars of Great Britain and Ireland, BSBI Handbook No. 4; Meikle; 1984.
As described in Stace''New Flora of the British Isles''; Clive Stace
Clive Anthony Stace (born 1938) is a British botanist and botanical author. He studied at King's College London, graduated from University of London in 1959 and then studied at the Natural History Museum, London. He was awarded a PhD in 1963. H ...
; Third edition; 2011 printing. and BSBI ''Salix arbuscula'' has the following characteristics:
* Twigs slightly hairy at first, later hairless and dark reddish brown.
* Leaves usually ovate up to 5 cm long by 3 cm wide; hairless and bright green on upper side; at first densely hairy on lower side, then hairless; margins with numerous small blunt teeth.
* Petiole short, occasionally up to 8mm long but usually less than 5mm.
References
{{Taxonbar, from=Q4195476 arbuscula Flora of Great Britain Flora of Norway Flora of Sweden Flora of Finland Flora of North European Russia Flora of East European Russia Flora of Kazakhstan Plants described in 1753 Taxa named by Carl Linnaeus