Genista sagittalis

This hardy, evergreen sub-shrub produced many clusters of typical yellow pea-like flowers in summer, but its foliage and form makes it unusual. Stems are hairy, light to mid-green  and with flattened wings, sometimes continuous or interrupted, giving its a distinctive look. In full sun and dry conditions, the stems will likely stay prostrate, or gently curving upwards, for many years. With a richer soil it will make a more spreading patch, with more vertical stems (to around 30cm). A good edging plant.