In many respects it is similar to the following species E. thimifolia. The latter may be distinguished by its non-sticky flowers, broad leaves with a bristle at the tip, the broad-based filaments and exserted anthers with minute appendages. E. filiformis is distinguished from the other species in the section by having exserted anthers without appendages, leaves that are linear and not open-backed and by having sticky flowers. The species is interesting botanically because of the variation in the number of stamens. The number, which is not constant but usually the same on one plant, varies from 4 to 8. Those plants with only 4 stamens would, technically, be classed as members of the genus Blaeria in which this is a feature. As most of the specimens have been recorded with 8 stamens, the species has been placed in the genus Erica.
Procumbent shrub, sometimes almost prostrate, much branched. Branches leafy, pubescent. Leaves 3-nate, 3-6 mm long, erect-spreading, usually shorter than the internodes, linear-subterete, sulcate, hirsute or glabrous, mostly with a tuft of white hairs at the apex. Flowers terminal, 3-nate or in clusters of 3-6; peduncles about 2 mm long, pubescent, slender; bracts approximate, small. Sepals 2 mm long, linear-subulate or narrow-lanceolate, acute, foliaccous, hirsute, shordy gland-ciliate. Corolla 2-5 mm long, suburceolate, tubular-urceolate or ovoid-urceolate, more or less contracted at the throat; usually tetragonous, viscid, glabrous, purple; lobes from the length of the tube, more or less spreading, semiovate, obtuse. Stamens usually 8, occasionally 4-7; filaments narrow, a little dilated, dark-coloured at the apex; anthers exserted or subexserted, 2/3-4/5 mm long, lateral or, rarely, subterminal, narrow-oblong, muticous; pore the length of the cell. Ovary globose, glabrous; style exserted; stigma subsimple.