Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but there has been disagreement over the way this should be done. As of 2017, it is widely (but not completely) accepted that the section that includes the majority of the Australian species should retain the name Acacia, whilst other sections of the genus should be transferred to other genera. This species is transferred to Senegalia[].

Common Name: Black Catechu

General Information

Senegalia catechu is a spiny, deciduous tree with slender branches; it can grow 10 - 20 metres tall. The bole can be 50cm in diameter[].
The tree is a source of tannins, known as 'catechu' or 'cutch', which has a wide range of uses including in medicine, as a dye and preservative, and as an ingredient of 'paan', a widely used mildly narcotic masticatory. The tree also provides a useful timber. It is extensively harvested from the wild, and also cultivated in Asia, and is an item of international trade[, , ].

Known Hazards

The bark contains an alkaloid and is said to be toxic[].
Both fruit and stem are used in Myanmar to poison fish[].
Especially in times of drought, many Acacia species can concentrate high levels of the toxin Hydrogen cyanide in their foliage, making them dangerous for herbivores to eat.

Botanical References

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Range

E. Asia - southwest China, Pakistan, India, Nepal, Bhutan, Myanmar, Thailand.

Habitat

Open, drier areas mostly on well drained soil types, but also on shallow, poor, rocky soils[]. Mixed deciduous forests and savannah of lower mountains and hills. Especially common in the drier regions on sandy soils of riverbanks and watersheds[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

A plant for sub-tropical to tropical areas, tolerating a minimum temperature of about 7°c[]. It is especially common in the drier regions, but can also be grown in the more humid climates of South-East Asia at elevations from sea-level to about 1,500 metres. It succeeds in areas where annual daytime temperatures acan reach 32 - 39°c, and the mean annual rainfall is in the range 500 - 2,000mm[, ].
Requires a sunny position[]. Grows best in a well-drained, neutral to acid soil[]. Succeeds in a wide range of soils, including poor, shallow ones[]. Intolerant of clay soils[].
The tree starts flowering and producing pods when 5 - 7 years old[].
Trees with a girth of 60 - 120cm are generally preferred for cutch production. The wood can be harvested when the trees are 30 years old in good sites, 50 years old in moderate sites, and 60 years old in poor sites. The whole tree is felled and transported to factories[]. The wood of freshly felled trees yields more cutch than dried wood[].
In 60-year-old plantations in India the yield of heartwood in good sites is 75 cubic metres per hectare, in moderate sites 63 cubic metres, and in poor sites 50 cubic metres. In these plantations the yield of cutch can be estimated at 6 tonnes per hectare, 5 tonnes and 4 tonnes respectively[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Catechu, obtained from the heartwood (see Other Uses below) is an indispensible ingredient of 'paan', a slightly narcotic chewing mixture containing betel leaf (Piper betle) and betel palm seed (Areca spp.) [].

The seeds contain water-soluble mucilage (6.8%); they are a good protein source but are nutritionally incomplete with respect to essential amino acids[].

Medicinal

Black catechu is a bitter-sweet antiseptic and astringent herb, the leaves, young shoots and bark of which are often used to check bleeding and discharges[]. The plant is strongly astringent, encouraging clotting of the blood and reducing excess mucous in the nose, large bowel or vagina[]. It is taken internally in the treatment of conditions such as dysentery, chronic diarrhoea and chronic catarrh[].
Externally, it is used as a wash etc to treat nose bleeds, haemorrhoids, skin eruptions, bed sores, mouth ulcers, sore throats, dental infections etc[].

When boiled, the wood and foliage of the tree produce a dark brown sticky substance known as 'catechu', 'cutch' or 'cachou'. This substance crystallizes upon cooling and has been an important article of trade in medicinal herbs since at least the 16th century, reaching Europe in the 17th century. It contains 25 - 60% tannins, 20 - 30% tannins, flavonoids and resins, and is valued mainly for its astringent qualities and is used both internally and externally to check bleeding and excessive secretions from the mucous membranes[, ]. In this form, the herb is subject to legal restrictions in some countries[].

The seeds have been reported to have an antibacterial action[].

Agroforestry Uses:

The plant is traditionally grown in living fences in the northwestern Himalayas, where it helps to exclude livestock and other animals; mark out land boundaries; whilst also providing a range of medicinal and other uses[].

Other Uses

The bark is a rich source of tannins[].
A khaki dye can be obtained from the bark[].

The bark exudes a light gum of very good quality and is one of the best substitutes for gum arabic[].
Obtained from Senegalia senegal, gum arabic has a wide range of uses including as a food additive, medicine and mucilage in inks etc[].

A tannin-rich, solid extract, known as catechu, or cutch, is obtained from the heartwood. Catechu usually contains 55 - 60% tannins[]. Depending on the way of processing, several products for different purposes can be obtained from this material:-
In India and Myanmar the dark 'catechu' or 'Pegu cutch' is used for tanning, often in a mixture of tan-stuffs. It is also used for preserving fishing nets and ropes; for dyeing cotton, silk, canvas, paper and leather a dark-brownish colour; and also as a viscosity modifier in on-shore oil wells[]. When dyeing cotton, the material is steeped for about one hour in a boiling solution of cutch, to which copper sulphate has been added. Afterwards it is transferred to a bath containing sodium bichromate. The dye is very fast to light, acids and alkalies[].
The crystalline portion of a concentrated decoction of the wood, called 'katha' or 'kath', is much used in betel chewing together with the leaf of Piper betle, and as an astringent for medicinal purposes[].
A third form of cutch is the crystalline deposit sometimes found in cavities of the wood, known in India as 'khersal'. It is used for medicinal purposes[].
After felling the trees, the bark and sapwood are removed, and the heartwood is converted into chips. In India the chips are extracted with water in extractors made of copper or wood, but vessels of aluminium and stainless steel are also suitable. After heating for about 2 hours, the chips are removed and extracted in a new bath of water. Then the extract is evaporated and cooled for crystallization to produce katha, which is separated by filtering[].
To obtain cutch the aqueous liquor is further concentrated in evaporators to a consistency at which it solidifies on cooling. In this way advantage is taken of the fact that cutch is soluble both in cold and hot water, whereas katha is only sparingly soluble in cold water[].

The heartwood is light red to reddish-brown, darkening on exposure; it is sharply demarcated from the yellow to yellowish white sapwood. The wood is very strong, very hard, durable and is not attacked by white ants or toredos[, ]. It needs long seasoning, and is fairly difficult to saw. Little known, but it is highly suitable for cabinet work[]. It is an important timber locally, where it is used for poles, agricultural implements, wheels, household items etc[, , ].
The wood makes an excellent fuel, and is ideal for making charcoal[, , ].

Propagation

The seed of most, if not all, members of this genus has a hard seedcoat and may benefit from scarification before sowing to speed up germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing. Seed germinates best at a temperature around 21°c[]. Sprouting commences around 5 - 7 days after sowing the treated seed[]. Plants quickly make a deep taproot and resent root disturbance, they should be planted out into their permanent positions as soon as possible[].
Semi-ripe cuttings of lateral shoots[].

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