Bolusanthus speciosus flowers

The tree wisteria flower has the typical shape of flowers of plants in the Fabaceae, pod-bearing or legume family.

The flower structure always has five fused sepals and five free petals. The flowers are generally hermaphroditic, meaning that both male and female reproductive structures are present in each flower.

Fabaceae the third biggest land plant family on earth, including such economically important plants as beans and peas. Only the Orchidaceae and Asteraceae families are larger in number of species.

Fabaceae plants are usually pollinated by insects. Some of them have actinomorphic or radially symmetric flowers, like the bauhinias. Most are, however, laterally symmetrical (zygomorphic) like pea-flowers and this species (Coates Palgrave, 2002; Wikipedia).