Siam Villa Garden: ต้นราชพฤกษ์

English Name: Golden Shower, Purging Cassia, Indian Laburnum, or Pudding-Pipe Tree

Scientific Name: Cassia fistula L.

Family: Fabaceae

Native Region: Southeast Asia

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. The tree has strong and very durable wood, and has been used to construct "Ehela Kanuwa", a site at Adam's Peak, Sri Lanka, which is made of C. fistula (ahala, ehela, or aehaela, ඇහැල in Sinhala) heartwood.

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.

In Ayurvedic medicine, the golden shower tree is known as aragvadha, meaning "disease killer". The fruit pulp is considered a purgative, and self-medication or any use without medical supervision is strongly advised against in Ayurvedic texts. Though it has been used in herbalism for millennia, little research has been conducted in modern times, although it is an ingredient in some mass-produced herbal laxatives. When used as such, it is known as "cassia pods".

In India, a cathartic made from the pulp is sometimes added to tobacco.