The flowers of Justicia petiolaris grow in dense stem-tip panicles. The calyx has five green, pointed lobes. The bracts below it are narrow and hairy, variable in length around 1 cm.
The corolla is two-lipped. The upper lip is small, holding the two stamens in a tiny channel. The lower one is large and three-lobed, the conspicuous floral part. The corolla is pale blue, its mouth white with dark mauve stripes. The flower is about 1,5 cm long.
Blooming happens from late spring to autumn (Manning, 2009; Pooley, 1998).