Narrow-leaved Lupin is an erect, robust, much branched annual herb or shrub with 5-9, narrow, finger-like leaflets, 1-6 mm wide, radiating from a central point. The flowers are arranged alternately and almost whorled near the top of the tall flower spike. The dark blue pea-type flowers are 10-15 mm long. The seed pods are 35-60 mm long, slightly flattened and sometimes a little constricted between the 2-6 seeds. The seed is smooth and mottled.
Native to the Mediterranean region, it is a common weed of roadsides and waste places, sometimes invading bush land and flowering in spring.