Pycnostachys reticulata is a robust, upright-growing, herbaceous shrub that reaches a height of 1.5 to 2 m. The leaves are opposite, narrowly lanceolate, with irregularly toothed margins and a very short stalk. When they are both not in flower, P. reticulata could be mistaken for Leonotis leonurus as they have a similar growth habit and similar-looking foliage.
Pycnostachys reticulata has pale blue and mauve flowers densely crowded into short, spikes, about 50 mm long and 20 mm wide. The inflorescence is terminal on the main or lateral branches. The flowers open from the bottom of the inflorescence upwards, forming a pale blue ring around the inflorescence.
It prefers a damp spot in the sun. It is not frost hardy.