Buddleja glomerata is fast growing and has an expected life span of 17 years. Several stems develop at the base of the plant and are covered in light brown, stringy bark. Young branches are flat, angled, light-green in colour and are covered with whitish hairs whereas older branches are light-brown. The young leaves are silvery green and fade to a bluish green when older. Leaves are oblong, 127 x 2-26 mm, arranged in opposite pairs on branches. The upper surface of the leaf is bluish green, rough textured, wrinkled and sparsely hairy. The lower surface is covered with white or brownish hairs and a clearly visible, thick midrib and lateral veins. Leaf margins are scalloped, wavy and lobed.Bright yellow flowers in dense heads are carried in panicles at the end of the branches, enhancing the foliage of the plant from September to March. The minute flowers are borne in dense, round heads. The yellow anthers of the stamens protrude from the flowers.

It has been recorded that the scent of the flower smells foul and the smell is supposed to be that of a cockroach; the pollen of the flower can cause sneezing, hence the common names cockroach and kakkerlak, sneezebush and niesbos. The fruit is a small, hairy capsule.