Calluna vulgaris is a diffuse, purple-flowered, evergreen shrub generally up to 60cm in height although unusually it may approach 1 metre and exceptionally more (Gimingham 1960). Because of its low stature it is classified as an undershrub (Rackham 1980) or as a dwarf shrub, although growth form can vary considerably with habitat. Where dominant it can form a very dense low canopy. It has numerous, tortuous, ascending branched stems, rooting at the base and bearing numerous short shoots. On shorter shoots the leaves are 1-2mm in size, linear and sessile, growing from two short projections at the base (Clapham, et al. 1987). They are longer and more widely spaced on longer shoots. Flowers are produced singly on short stalks.