Banyan trees are so common in Kerala and also all over India. In fact, for the rest of India, apart from Kerala, the banyan tree is called as the "Kalpavriksha".
Banyan tree is unique because of its aerial roots, hanging down from the branches, known as prop roots. Why? Because these roots perform the function of propping up the tree. The banyan tree can grow very fast & over a very large area. Then, it becomes difficult for the central trunk to support the weight of the entire tree. Then, the tree sends down prop roots from its branches which bind them more firmly with the earth. Eventually, these roots grow into thick trunks and clump together resemble the main trunk.
The germination and the later growth of the tree is also unconventional. The seed germinates in the hollows of other trees or in cracks in buildings. After germination, the seedling sends down its roots towards the ground. Later, these roots coalesce to form a pseudo trunk, gradually strangling and killing the host tree.
The banyan tree is native to India. It has cultural and religious significance for the Hindus and the Buddhists as the Buddha attained nirvana while meditating under a banyan tree. The banyan tree has various medicinal uses, both in the traditional Indian system of medicine and the Western system. The sap from the tree is used as an inferior alternative to rubber. Pulp from the tree is used to make paper. Handicrafts are built using the tree's wood.
The tree, due to its large structure, is also useful in other ways. It provides shade & refuge for people & birds respectively. Its large size helps to prevent soil erosion & also assists in cleaning up the air around it.