Black cutch (Senegalia catechu P.J.H. Hurter & Mabb., formerly known as Acacia catechu (L.) Willd., Oliv.) is a moderate-sized deciduous tree native from Asia which is valued for the production of tannin ("cutch") extracted from its heartwood. Its branches are extensively lopped for fodder before leaf fall (Orwa et al., 2009).
Morphology
Senegalia catechu is a small or medium-sized, thorny tree up to 15 m tall. Its taproot grows to 2 m deep (CRC Weed Management, 2003). Its bark is dark grey or greyish-brown, peeling off in long strips, or sometimes in narrow rectangular plates, brown or red inside. The branches are shiny, slender, puberulous when young but glabrescent after, the base of each petiole bearing 2 curved, 8-mm long prickles. The leaves are bipinnately compound, with 9-30 pairs of pinnae and a glandular rachis. Each pinnae has 16-50 pairs of oblong linear leaflets, 2-6 mm long, glabrous or pubescent. The inflorescence is a 5-10 cm long axillary spike of small pentamerous flowers, white to pale yellow in colour, with conspicuous stamens exserted from the corolla. The fruit is a beaked pod, 5-8.5 cm x 1-1.5 cm, flat, shiny, brown, dehiscent. It contains 3-10 flat, ovoid, dark brown seeds, 5-8 mm in diameter (CRC Weed Management, 2003). There are 15,000-40,000 seeds/kg (Subansenee, 1991).
Senegalia catechu var. catechu, var. catechuoides and var. sundra occupy different areas in India. Var. catechu is found in the sub-Himalayan tract and the outer Himalayas, and ascends up to 900-1200 m elevation. Var. catechuoides is found in Sikkim terai, West Bengal and Assam (it is also the main variety in Burma). Var. sundra occurs in the Deccan, Maharashtra, Gujarat and Rajasthan.
Uses
Senegalia catechu is a valuable fodder tree for goats and cattle, and its slender branches are lopped before main leaf fall. The seeds are a source of protein though they have unbalanced amino acid content and a high content of water soluble mucilage. The tree is a host for lac insects. Both fruit and stem are used in Myanmar to poison fish (Subansenee, 1991). Flowers are attractive to bees and provide an excellent source of nectar and pollen (Kumar et al., 2016). Black cutch is used as live fence (Subansenee, 1991). Senegalia catechu provides a highly calorific firewood that also makes good quality charcoal. Its high density wood is resistant to white ants and is used for posts, agricultural implements and wheels.
The heartwood of Senegalia catechu yields a tannin called cutch, which yields different products:
- Dark catechu called "pegu cutch" helps tanning heavy hides.
- Catechu extract is a preservative for nets and ropes and is used for dyeing textiles, paper and leather to a dark-brownish colour.
- The crystalline portion of a concentrated decoction of the wood, called 'katha' or 'kath', is mixed with betel (Piper betle) leaves to produce betel chewing paste (Subansenee, 1991). In France, it is an ingredient of the famous century-old confectionery "Cachou Lajaunie".
Katha, khersal (a natural crystalline deposit sometimes found in cavities of the wood) and other parts of Senegalia catechu (bark, seeds) are reported to have uses in ethnomedicine, such as treatment cough and sore throat, wound healings, antidiarrhoea, antibacterial, etc. (Subansenee, 1991).
