Talinum triangulare (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Talinum triangulare (Jacq.) Willd.

Protologue: Sp. pl. 2: 862 (1799).

Family: Portulacaceae

Chromosome number: 2n= 48, 72

Synonyms

• Portulaca triangularis Jacq. (1760),
• P. racemosa L. (1762),
• Talinum racemosum (L.) Rohrb. (1872).

Vernacular names

• Waterleaf, Surinam purslane, sweetheart (En)
• Grassé (Fr)
• Indonesia: poslen (West Java), krokot belanda
• Papua New Guinea: kumu manus
• Philippines: talilong (Tagalog), galaghati (Subanon), biala (Marinduque)
• Thailand: som-kaoli (Bangkok), som-khon (Bangkok), som-chin (northern)
• Vietnam: thổ nhân sâm.

Origin and geographic distribution

Waterleaf is probably native to tropical America. Its complete native range, however, is difficult to ascertain because it is easily transported and easily naturalizes. Waterleaf has become a weed with pantropical distribution, still extending its range. It was introduced into Java in 1915 from Surinam by the Bogor Botanic Gardens. Elsewhere in South-East Asia its introduction is also relatively recent.

Uses

The leaves and shoots are usually consumed as a cooked (boiled or steamed) vegetable. They are rather soft and mucilaginous and should not be cooked for long. They are also added raw to salads in the Sundanese cuisine in West Java. It is a good alternative for purslane (Portulaca oleracea L.).

In South-East Asia waterleaf is sometimes planted as an ornamental pot plant or as an edging plant in gardens. In South America it has some medicinal applications. The crushed plant is applied as a poultice on contusions, inflammations and tumours. Decoctions are used for painful eyes and to aid recovery from blows and falls.

Production and international trade

In Africa, South America and the Caribbean, waterleaf is a popular leafy vegetable. In South-East Asia it is a rather recent introduction and is still of minor importance. No statistics are available.

Properties

Per 100 g edible portion, waterleaf contains: water 90-92 g, protein 1.9-2.4 g, fat 0.4-0.5 g, carbohydrates 3.7-4.0 g, fibre 0.6-1.1 g, ash 2.4 g, Ca 90-135 mg, Fe 4.8-5.0 mg, β-carotene 3 mg, vitamin B₁ 0.08 mg, vitamin B₂ 0.18 mg, niacin 0.30 mg, vitamin C 31 mg. The energy value is 105 kJ/100 g. Waterleaf has a rather high oxalate content. The weight of 1000 seeds is 0.3 g.

Botany

• Erect perennial herb with swollen roots and obtuse-angular to terete, glabrous, succulent stems, 30-100 cm tall. Branches with 2 lateral, basal buds.
• Leaves spirally arranged to nearly opposite, often crowded at the top of the stem, indistinctly or shortly petioled; leaf-blades usually spathulate, 3-15 cm × 1-6 cm, entire and succulent, obtuse to rounded and occasionally notched at the apex.
• Inflorescence a long peduncled, terminal, corymboid thyrsus, 5-30 cm long, with 2-5 erect, sharply triangular axes, each 8-28-flowered; flowers bisexual, 0.5-2.5 cm in diameter; pedicels elongate after anthesis; sepals 2, free, green, persistent; petals 5, obovate, up to 10 mm × 4 mm, pink; stamens 20-40; style 2-3-fid, ovary superior.
• Fruit capsular, ellipsoid to globular, 4-7 mm long, 2-3-valved and elastically dehiscent, yellow.
• Seeds numerous, compressed globose-reniform, 0.8-1.2 mm long, granulate, glabrous, shining black.

Waterleaf is fast-growing, and once established it easily reseeds itself. It flowers early and year-round, and is mainly self-pollinating. Flowers are open in the morning.

T. triangulare is most easily distinguished from T. paniculatum (Jacq.) Gaertner (a pantropical weed, primarily used as ornamental but also occasionally consumed as vegetable in South-East Asia) by its sharply triangular flowering axes (terete in T. paniculatum).

Ecology

Waterleaf occurs naturally on roadsides, waste places, and forest edges, from sea-level up to 1000 m. It has a C4-cycle photosynthetic pathway, resulting in a high level of dry matter production under hot tropical conditions. It possesses a remarkable degree of drought tolerance. For good production it needs a soil rich in humus or heavily manured, and adequate moisture.

Agronomy

Waterleaf is usually propagated by seed. However, the small seeds are rather difficult to collect because the fruits readily dehisce. Seeds are broadcast, direct-seeded in rows, or sown in a seed box and transplanted. The delicate seedlings must be shaded and mulched. Waterleaf can also be propagated vegetatively. Cuttings 15-20 cm long are taken from mature stems which have been stripped of leaves. Plant densities vary from 10-25 plants/m²depending on harvesting method and crop duration. Waterleaf flowers early but this seems to have little negative effect on leaf production. No serious diseases or pests are known.

Harvesting starts about 6-8 weeks after sowing, either by uprooting or by cutting the young tops. 15-20 harvests (at intervals of 2 weeks) can be made, but it is usually advisable to renew the planting after about six months. Yields have been estimated at 10 kg per m² per year (15-20 harvests). Seed yields are low and amount to 100-300 kg/ha. Seed production in untopped plants reaches a peak about 10 weeks after sowing.

Genetic resources and breeding

No substantial germplasm collections exist. A few landraces have been collected in the Philippines and are being maintained at the National Plant Genetic Resources Laboratory, Institute of Plant Breeding, Los Baños. No breeding work has been carried out.

Prospects

Waterleaf, with its slimy texture, is a popular vegetable in many African countries. It spreads easily and is becoming a general, though rather innocent, agricultural weed. Agronomic research and breeding work should be done on this interesting vegetable.

Literature

• Geesink, R., 1971. Portulacaceae. In: van Steenis, C.G.G.J. et al. (Editors), 1950- . Flora Malesiana. Series 1. Vol. 7. Noordhoff International Publishing, Leyden, the Netherlands. pp. 123-125.
• Ochse, J.J. & Bakhuizen van den Brink, R.C., 1980. Vegetables of the Dutch East Indies. 3rd English edition (translation of "Indische Groenten", 1931). Asher & Co., Amsterdam, the Netherlands. pp. 620-621.
• van Epenhuijsen, C.W., 1974. Growing native vegetables in Nigeria. FAO, Rome, Italy. pp. 92-94.
• van der Zon, A.P.M. & Grubben, G.J.H., 1977. Les légumes-feuilles spontanés et cultivés du Sud-Dahomey [Wild and cultivated leaf vegetables of South Dahomey]. Communication 65. Department of Agricultural Research, Royal Tropical Institute, Department of Agricultural Research, Amsterdam, the Netherlands. Communication 65. pp. 97, 99.

Authors

• M.A. Rifai