It is full summer in the Southern hemisphere now (i.e. October to March) which often means generous flowering among tropical ornamental trees. We were amazed in November with the purple-violet jacaranda trees followed by the stunning flame of the forest (Delonix regia) in December while January brings us another flowering jewel. We keep traveling around the rainbow colors and hit yellow this time.
Of course the clue was given in the title "golden shower tree'" which indeed calls for rich yellow gold masses of flowers that can turn the tree in a fantastic vegetal sun given the fact that leaves shed during the dry season and thus the first flowers appear on bare branches. Its other vernacular names such as "Indian laburnum" or "lluvia de oro" insist on the spectacular color, so do the French names such as "douche d'or" and "cytise Indien'", while "cassier", "caneficier" or "faux caroubier" insist on the pods. Our tree's scientific name is Cassia fistula, it does belong to the very large Fabaceae botanical family. The Cassia genera contains some 30 species of trees and shrubs from tropical areas. This one comes from southern Asia (Pakistan, India, Sri-Lanka, Myanmar). As it is a rather easy to grow plant and with such ornamental effect it has logically spread around the tropics and is nowadays common sight from Africa to America and from Asia to Australia, usually in coastal parts but in Pakistan it can be found at mountain elevations. It requires full sun and well drained soils and can withstand drought and sea-spray. Mildew and iron chlorosis can affect the tree and roots are often prone to bacterial and fungi attacks. Fasciated or crested shoots and even fruits can also be seen. Propagation can be done by cuttings, layerings or sowing, if seeds are to be used they will require acid treatment and/or tegument scraping to help sprouting as the outer coat is rather strong, a seed can reach three times its volume by absorbing water.
The tree is a rather fast-growing one which can reach 10 to 15 meters (30 to 45 feet) high, young bark is smooth and grey while it will turn brown and rough with time. Leaves are pinnate as for many members of this family. They are up to 30 to 40cm (one foot) long and made of three to eight pairs of shiny leaflets, young shoots with leaves can be used as fodder. Flowers are made of pendulous clusters which can be 20 to 40cm (about a foot) long, they turn into pods which are black shiny rounded fruits between 20 and 50cm (about a foot) long. The flower has been chosen as national flower for Thailand, where it stands for Thai royalty and in the Indian state of Kerala it has also been adopted as symbol while the real flowers are of prime importance during Vishnu celebrations.
The wood is of good quality, rather hard and is used in India to make poles, carts, pavings, bridges, agricultural tools and so on. The bark contains compounds which are used to dye fabrics in red color and the ashes make an efficient color fixative. But the most useful and potent part is found in the pods which when open, show a series of small separated compartments containing one seed surrounded by a black sticky pulp. This edible stuff is quite palatable but one should be careful and not eat too much as the thing is powerfully laxative and purgative, such properties have been recognized and put to use for ages by people around the world. In Tanzania, Zimbabwe and Mozambique the fruit is used to fight malaria and carbuncles while it gives fragrance to tobacco in Bengale. In New-Guinea broken limbs are cured by wrapping them in bark scrapes and sap. In Thailand, wounds and ulcers are treated with roots decoction, the bark and leaves are also efficient to treat skin disorders. In parts of Latin America the pods are used against diabetes. In former times powdered seeds have been turned into eye drops though those same seeds are reputedly toxic.
So the next time you travel to the tropics, check in the surroundings. If this tree happens to be growing, you can enjoy the massive flowering or indulge into some pulp after breaking a pod, but do not over-indulge!