Khair (Acacia catechu) is a moderate size deciduous tree with rough dark gray brown bark. It belongs to family Leguminoseae-mimoseae. It is said that the name catechu' was given to it because its bristles resemble the claws of animals of the cat family or maybe because its heart wood contains cutch. It is also called khoira, koir, kheriya baval, kher babul, kagli, cachu, kugli, kaderi and sandra in local Indian languages (Hindi, Punjabi).
Khair grows naturally all over Haryana and the rest of Indian subcontinent areas experiencing average rainfall, in the whole of the Indo Gangetic plain from Assam westwards, right up to Afghanistan. Also from sea coast to Deccan Plateau and then northwards to the lower Himalayan ranges having an altitude up to about 1250 m or so.
Khair grows well on all kinds of geological formations and soils, but porous alluvium consisting of sand and shingle suits it best. It grows on granite, gneiss, schist, quartzite, shale, basalt, trap, limestone conglomerate, laterite, etc. and also on black cotton soil. Khair grows slowly and matures to a height of about 10 meters in about 55 years. The diameter of the trunk is about 30 to 40 cm, and it is seldom straight. Instead, it generally tends to be crooked with an irregular shaped crown. Its bark is gray in color and nearly 8 mm to 12 mm thick. It tends to come off in small patches of irregular shape.
Khair (Acacia catechu) is generally leafless during late spring to early summer. Old leaves are generally shed during Jan-Feb and new ones appear during April-May. The species gets full foliage by June-July when it paints the environment and landscape so very beautifully. The leaves of khair are compound. The rachis branching from the mid-rib has 4 to 5 round prickle. The rachis is nearly 10 to 20 cm long and bears 20 to 60 pinnae each about 3 to 4 cm long. The khair tree flowers during June to October. Its inflorescence is pale yellow to cream colored. The fruit of khair is pod shaped. It is 5 to 7 cm long and 1 to 1.5 cm wide and shining brown in color.
The sap wood of khair is large and yellowish white and heart wood is small and red in color. The wood darkens on exposure. Sap wood weighs about 20 kilogram and heart wood weighs 25 to 28 kilogram per cubic foot. While the sap wood is liable to be attacked by a variety of insects, the heart wood is too hard to be attacked by any of such insects.
The wood being hard is used for making rice pestles, hookah stems, rollers for crushing sugar cane and oilseeds, ploughs, handles for knife, daggers and swords. The wood is also used for making quality charcoal which is eagerly sought by gold, silver and blacksmiths. While the wood is smooth and lustrous, and takes good polishing, it is not used in house construction because of superstition.
The khair tree is very useful in a number of ways. A pale yellow mucilaginous gum exudes from the tree, yielding one of the best substitutes for true gum arabic. Its wood contains catechin, catechutanic acid and tannin. The wood extracts are used for tanning and dyeing khaki.
The bark and roots of khair are used in treating sore mouth, body pains, gravel, bronchial asthma and indigestion. The bark is especially useful as astringent, and a cure in cough, diarrhea and indigestion, cancer, piles, sore throat, ulceration, eczema and certain forms of leprosy.
Katha is a white substance found in Khair wood. It is obtained by boiling small chips of the heart wood in specially designed earthen pitchers and allowing the concentrate to cool and crystallize. Katha is not only used as a remedy for body pain but also in medicines for other human ailments. Katha is also used extensively in pan. It forms an important ingredient of adhesives for plywood and is also extensively used in drying canvas and sizing of fishing nets and ropes.
Because of their various uses, Khair tree wood, bark and roots are in great demand. While the going price of a standing khair tree of approximately one-foot diameter is about Rs 2000, the Katha sells at nearly Rs 600 per kg. The bark fetches nearly Rs 20 per kg. The tree has always been subjected to extensive exploitation both legal as well as illegal.
Khair tree regenerates quite abundantly in suitable soil and moisture conditions, the growers tend to assist the nature artificially to stock the vacant areas with this species at a quick pace. For that its seeds are collected during winter and sown in polythene bags during spring. The transplanting of the seedling is best done during the rainy season. In natural habitat it can be raised easily by direct sowing as well.