1393

3: Dye and tannin-producing plants

Butea monosperma (Lamk) Taubert

Engler & Prantl, Nat. Pflanzenfam. 3(3): 366 (1894).

LEGUMINOSAE

2n = 18 (+ B), but also recorded as 22 and 32

Butea frondosa Roxb. ex Willd. (1802).

Flame-of-the-forest (En). Indonesia: palasa (general), plasa (Javanese, Sundanese). Burma: pouk-pen. Cambodia: chaa. Laos: chaan. Thailand: thong kwaao, tong thammachaat.

Flame-of-the-forest is found in the southern Himalayas of Nepal, throughout India, Sri Lanka, extending to Burma, Thailand, Indo-China and Java. It has been spread eastward as far as China and Papua New Guinea. Locally, it has been successfully established in tropical Africa, and in subtropical regions.

Flame-of-the-forest can be considered as a multipurpose tree. It has dyeing as well as tanning properties. A bright yellow to deep orange-red dye can be prepared from the flowers, especially used for dyeing silk, sometimes cotton. This dye is used by Hindus to mark the forehead. A red exudate is obtained from the bark, hardening into a gum, known as 'Butea gum' or 'Bengal kino'. It can be used as a dye and as a tannin, and has medicinal properties as a powerful astringent and is applied in cases of diarrhoea. The seeds show anthelmintic activity, and also bactericidal and fungicidal effect. The flowers are useful in the treatment of liver disorders.
The coarse, fibrous material obtained from the inner bark is used for rough cordage, for caulking the seams of boats and for making paper.
In India the tree is an important host for the lac insect (Laccifer lacca), producing shellac. Of all lac trees, it yields the most stick lac per ha. The wood is not considered of great value, but it is sometimes used for utensils and for constructions, more commonly for fuel. It is used by Hindus in religious ceremonies.
Flame-of-the-forest is also planted as an ornamental because it flowers with a profusion of bright orange, rarely sulphureous flowers.
It is a valuable species for reclaiming saline soils.

The orange dyeing substance from the flowers is butein. By extracting the flowers with boiling water and hydrolizing the extracted glycoside butrin, a yield of 2% butin (C₁₅H₁₂O₅) is obtained. The colourless butin can easily be transformed into butein by boiling with potassium hydroxide. Butein is very fugitive. Butrin and isobutrin are the antihepatotoxic principles in the flowers.
Butea gum is ruby-red. It contains about 50% tannins, and pyrocatechin, arabine and ulnine.
The seeds contain butin and ca. 20% of a yellow oil. Anticonceptive activity has been demonstrated in rats fed with seeds. Seed-coat extracts have bactericidal and fungicidal effect.
A potential anti-asthmatic agent has recently been reported from the bark.
The soft and not durable wood is light, ca. 570 kg/m³ air dry, white or yellowish-brown when fresh, but often turning greyish because of susceptibility to sapstain.

A small to medium-sized leaf-shedding tree, 5—12(—20) m tall; trunk usually crooked and tortuous, with rough greyish-brown, fibrous bark, showing a reddish exudate; branchlets densely pubescent. Leaves trifoliolate; petiole 7.5—20 cm long with small stipules; leaflets more or less leathery, lateral ones obliquely ovate, terminal one rhomboid-obovate, 12—27 cm x 10—26 cm, obtuse, rounded or emarginate at apex, rounded to cuneate at base, with 7—8 pairs of lateral veins, stipellate. Flowers in 5—40 cm long racemes near the top of usually leafless branchlets; calyx with campanulate tube and 4 short lobes; corolla 5—7 cm long, standard, wings and keel recurved, all about of the same length, bright orange-red, more rarely yellow, very densely pubescent; stamens enclosed within the keel, 9 connate and 1 free; ovary superior, with curved style. Fruit an indehiscent pod, (9—)17—24 cm x (3—)4—6 cm, stalked, covered with short brown hairs, pale yellowish-brown or grey when ripe, in the lower part flat, with a single seed near the apex. Seed ellipsoid, flattened, about 3 cm long.

While germinating the seed remains in the pod which opens at the tip and allows the young shoot and root to emerge. The cotyledons remain attached to the seedling for a considerable time. The tree is slow growing. Leaves are shed during dry weather. At the beginning of the rainy season the leafless tree flowers abundantly and it is very conspicuous in the forest then. At the end of the flowering period, new leaves develop which are initially pale bronze-tinged green. Birds are the chief pollinators.

From a few places in India a yellow-flowered form has been reported which has been named var. lutea (Witt) Maheshwari.

Naturally, flame-of-the-forest grows commonly in open grasslands and scattered in mixed forest. In the Himalayas it is found up to 1200 m altitude, in Java it is confined to relatively dry regions in the east, up to 1500 m altitude. Plantations can be established on irrigated as well as rainfed lands. This tree survives in saline and badly drained soils on which few trees will grow. It is not only drought-resistant but also frost-hardy.

Trees are propagated by seeds. Before the beginning of the rainy season, complete pods are sown in rows 3—6 m apart. Seedlings thrive best on a rich loamy soil with pH 6—7 under high temperature and relative humidity. Root suckers are freely produced and enable vegetative propagation and easy tree recovery after damage.

Flowers collected for dyeing purposes are dried. Silk can be dyed yellow with a decoction or infusion from dried flowers. The colour is not fast except when a mordant like alum or lime is used, which also deepens the colour to orange. For dyeing cotton and wool the glycoside in the flowers must first be hydrolyzed, for instance by boiling with a solution of hydrochloric acid.

As a multipurpose tree, flame-of-the-forest deserves more attention. It combines interesting dyeing and tanning properties with medicinal and ornamental qualities. The tree is especially promising as an ornamental, but it is difficult to propagate and to grow because it does not produce many seeds and is slow-growing. Research on faster ways of vegetative propagation should have priority.

Anonymous, 1979. Tropical Legumes: resources for the future. National Academy of Sciences, Washington D.C., USA. pp. 245—246.
Backer, C.A. & Bakhuizen van den Brink, R.C., 1963. Flora of Java. Vol. 1. Noordhoff, Groningen, the Netherlands. pp. 628—629.
Bhatnagar, S.S. (Editor), 1948. The wealth of India. Raw materials. Vol. 1. Delhi. pp. 251—252.
Mayer, F. & Cook, A.H., 1943. The chemistry of natural coloring matters. Reinhold Publishing Corporation, New York. pp. 177—178.

K. Chayamarit

Chayamarit, K., 1991. Butea monosperma (Lamk) Taubert. In: Lemmens, R.H.M.J. and Wulijarni-Soetjipto, N. (Editors): Plant Resources of South-East Asia No 3: Dye and tannin-producing plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea