Catechu (khayer) kind of tannin extracted from the heart-wood of the khadir tree (Acacia catechu), a dicotyledon deciduous and leguminous tree of the pulse family, native to the Indian subcontinent and its adjoining areas. In Bangladesh, India, Nepal, Bhutan, Pakistan, Sri Lanka and Malaysia, catechu has been in use since ancient times as a spice with betel leaf (Pan). Those who are accustomed to chewing betel leaf will not get the real taste if they do not take khayer with it. Catechu brings added pleasure to the chewing of betel leaf. A small bit of khayer added to the betel leaf adds to the taste and makes one's lips red.

Catechu is of two kinds - white catechu and brown catechu. White catechu is more useful and is familiar as Papdi Khayer. Brown catechu is widely used as a dye in painting and cloth dying. There are also five types of catechu used as spices of betel leaf - Papdi, Janakpuri, Pegu, Tili and Belguti. The aromatic Keya Khayer is also worth mentioning. The tannin collection process from catechu tree is different from that of the rubber tree. In the case of the rubber plant, tannin is extracted directly from the section of the cut-up barks on the tree. But in the case of catechu, branches or stems are cut into small pieces and are put under water for a few days. The tannin is secreted into water and the raw catechu or stone khayer is prepared by evaporating the solution.

The catechu tree has herbal uses and its leaf, bark and tannin are used as indigenous ayurvedic medicine for some diseases. Many blood purifying tonic (Salsa) are being made from khadir tree. Of them Khadiratrist is said to cure incurable diseases such as leprosy, jaundice, enlargement of the spleen etc.

Catechu timber is very hard and free from termite and wood-borers' attack and is used in heavy duty operations such as building a house pillar, cart-wheel, plough, husking-pedal (dheki), etc. It is also a very good quality fuel wood. The lac insect is cultivated on the catechu tree.

Catechu tree or khadir tree is found widely in the northern part of the country - Dhamoirhat, Gobindaganj, Charghat, Rajshahi, Debiganj, Nawabganj, Dinajpur, Khansama, Birganj and Haripur areas, and can be found especially in barind tract region. The tree also grows in abundance in Koch Bihar and Jalpaiguri of west bengal in India. Most of the demand for khayer in the country is met locally, but it is also imported from Malaysia. However, Bangladesh produces the best quality khayer. [Md Mahbub Murshed]