Cassia fistula, commonly known as golden shower, purging cassia, Indian laburnum, or pudding-pipe tree, is a flowering plant in the subfamily, Caesalpinioideae of the legume family, Fabaceae. The species is native to the Indian subcontinent and adjacent regions of Southeast Asia. It ranges from eastward throughout India to Myanmar and Thailand and south to Sri Lanka and southern Pakistan. It is a popular ornamental plant and is also used in herbal medicine. It is both the national tree and national flower of Thailand. It is the state flower of Kerala in India. It is the provincial flower of North Central Province in Sri Lanka.
The golden shower tree is a medium-sized tree, growing to 10–20 m (33–66 ft) tall with fast growth. The leaves are deciduous, 15–60 cm (6–24 in) long, and pinnate with three to eight pairs of leaflets, each leaflet 7–21 cm (3–8 in) long and 4–9 cm (1.6–3.5 in) broad. The flowers are produced in pendulous racemes 20–40 cm (8–16 in) long, each flower 4–7 cm (1.6–2.8 in) diameter with five yellow petals of equal size and shape. The fruit is a legume, 30–60 cm (12–24 in) long and 1.5–2.5 cm (0.6–1.0 in) broad, with a pungent odor and containing several seeds.
C. fistula is widely grown as an ornamental plant in tropical and subtropical areas. It blooms in late spring. Flowering is profuse, with trees being covered with yellow flowers, many times with almost no leaf being seen. It grows well in dry climates. Growth for this tree is best in full sun on well-drained soil; it is relatively drought-tolerant and slightly salt-tolerant. It will tolerate light brief frost, but can get damaged if the cold persists. It can be subject to mildew or leaf spot, especially during the second half of the growing season. The tree blooms better with pronounced differences between summer and winter temperatures.
Pollinators and seed dispersal
Various species of bees and butterflies are known to be pollinators of C. fistula flowers, especially carpenter bees (Xylocopa sp.). In 1911, Robert Scott Troup conducted an experiment to determine how the seeds of C. fistula are dispersed. He found that golden jackals feed on the fruits and help in seed dispersal.
In India, flowers of the golden shower tree are sometimes eaten by people. The leaves have also been used to supplement the diets of cattle, sheep, and goats fed with low-quality forages.