Buddleja polystachya is a multi-branched shrub or occasionally small tree endemic to the semi-arid highlands flanking the Red Sea in Eritrea, Ethiopia, Saudi Arabia, Somalia and Yemen, where it grows in secondary scrub or around forest, often along watercourses, at elevations of between 2,200 and 3,600 m; its range extends southward into the highlands of Kenya and Tanzania. Buddleja polystachya usually grows to < 5 m, but can occasionally reach 12 m in favourable conditions. The bark can be either red-brown or grey in colour. The flowers are generally bright orange, forming dense panicles < 20 cm long; however, specimens found in Saudi Arabia bear flowers with yellow corollas, and only the lobes are orange. The leaves are < 15 cm long and narrow, with a pointed tip, the upper surface a pale grey-green. The fruit is a small dry orange capsule.