Loosely to densely bushy or mat-forming, to 20cm tall. Leaves 1cm long shining green, lanceolate. Flowers yellow, to about 2cm across. Variable with five subspecies, of which alpestre (syn. H, alpestre) from southern Europe is very neatly matted, and is the form most commonly grown, sometimes as H, serpyllifolium (which does not appear to be a valid name). It is a distinct, neat, well-flowered hardy plant. Subsp. oelandicum (Sweden), italicum (Mediterranean), rupifragum (eastern and southeastern Europe) and orientale (Crimea) show only minor differences.