Shrubs or trees up to 20-30 m high . The bark is thin, smooth, gray-brown. The branches are thin, slightly twisted.
The leaves are pinnate, fern-like - more often double-pinnate, less often pinnate or simple.
The flowers are collected in apical brushes, usually of all kinds of bluish and lilac shades, there are also species with white and purple flowers. The corolla is five-petalled; a strong smell is characteristic of flowers.
The distinctive features of the genus are the presence of staminodium in the flower, exceeding the length of the stamens, three-bordered pollen and the number of chromosomes 18.
The fruit is an elongated or rounded box with numerous small seeds. When growing in a culture from seeds, the first flowering of the plant has to wait a very long time.