Each bilaterally symmetrical flower has a large, rounded, five-angled pinkish calyx, the four lobes being tipped with teeth, which can easily be observed before the flower has opened. The flower is pinkish-purple with white markings in the throat, and up to 2.5 cm (1 in) in length. The five petals are fused into a tube, the upper lip is curved into a hood, having two teeth at the tip.