Trifolium repens (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Trifolium repens L.

Protologue: Sp. Pl.: 767 (1753).

Family: Leguminosae

Chromosome number: 2n= 32 (tetraploid), but 16, 28, 48 and 64 occur as well

Vernacular names

• White clover, Dutch clover (En). Trèfle blanc (Fr)
• Indonesia: semanggi landa (Javanese)
• Thailand: thua clover.

Origin and geographic distribution

The likely centre of origin is the Mediterranean region but white clover is indigenous to the whole of Europe, Central Asia west of Lake Baikal, and to small areas in Morocco and Tunisia. It is naturalized in many countries, particularly in North America, China, Australia and in higher latitudes of South America. Although of most importance in mild temperate and Mediterranean climates, white clover is naturalized in the higher rainfall subtropics and in the elevated tropical areas such as the highlands of Papua New Guinea.

Uses

In the tropics and subtropics, white clover is used as a forage legume in grazed pastures. It is also an important species for pasture hay and silage in temperate regions. The flowers are considered as an important source of honey.

Properties

White clover is one of the best quality temperate legumes and is better in quality than any tropical legume. Nitrogen percentages in foliage range from 3.5-5% and DM digestibilities range from 60-80%. Cultivars adapted to warmer climates tend to have higher glycoside levels, but not high enough to affect animal production. There are 1400-1800 seeds/g.

Botany

A perennial herb which, particularly in subtropical areas, can also persist as an annual. The primary taproot seldom persists for more than one year (subtropics) or two years (temperate areas). The prostrate succulent stolons which develop shallow adventitious roots are short-lived, usually for less than one year. Leaves trifoliolate, long-petioled (1-30 cm); leaflets elliptical to obovate to heart-shaped, 0.5-4 cm × 1-1.5 cm, margin denticulate, glabrous, frequently with white or light green markings that are often crescent shaped; petiole length and leaflet size vary markedly with cultivar and decrease with increasing grazing pressure. Peduncle 2-30 cm long, glabrous; inflorescence umbellate, globose, 1.5-3.5 cm in diameter, with up to 40 white or light pink flowers, reflexed after fertilization; calyx 3-5 mm, corolla 4-13 mm long. Pod linear-oblongoid, 4-5 mm long, with 3-4 seeds. Seed ovoid to reniform, ca. 1.5 mm long, usually pale yellow, occasionally reddish-brown.

White clover is a very variable species, and mainly based on flower colour and size of flowers and leaflets, numerous botanical varieties have been distinguished. No satisfying classification exists. There are numerous cultivars of white clover, for description purposes roughly classified based on size into small, intermediate and large types. Two widely used ones in the subtropics are "Haifa" and "Louisiana S1", both being heavier seeders in the subtropics than "Ladino" or "Grassland Huia".

In temperate areas white clover grows actively during summer. In contrast, in the subtropics it grows in the cooler months with a peak late in spring if there is adequate moisture. There is considerable stolon death over late summer and early autumn. This death is associated with high minimum and maximum temperatures and also with moisture stress during dry periods, with rotting of roots and stolons in wet conditions, and with competition from warm season grasses. Growth from late autumn onwards is then from surviving stolons and from seedlings which emerge until early spring. Soil seed reserves can reach 10 000 seeds/m²in good white clover pastures in the subtropics, whereas poor pastures may have less than 1000 seeds/m².

Ecology

White clover does not grow well on drought-susceptible soils with low soil moisture storage or on waterlogged soils, particularly where waterlogging coincides with high temperatures. White clover requires high levels of fertility, with a pH(H₂O) of over 5.0 and preferably 5.5., and available soil P levels of over 20 mg/kg. It is susceptible to high levels of available soil Mn and Al.

Agronomy

Although hand-harvested seed of white clover is hard-seeded, commercial seed usually has low levels of hard seed. Under favourable conditions it can be established by broadcasting into closely grazed pastures, but there is more prospect of success with sowing into rough cultivation or a fully prepared seed-bed. Seed should be inoculated with an appropriate Rhizobium strain before sowing if it is sown in an area where it has not been grown before. White clover based pastures should be well grazed, especially during the summer period when the companion grasses are growing quickly and the clover is growing under adverse temperature conditions. Bloat (tympanitis) can be a problem in spring when clover growth is vigorous and there is little grass in the pasture. Probably the most important diseases are those associated with weak pathogens such as Pythium middletonii which attack stolons and roots during wet and hot conditions during summer. Rust pustules on leaves caused by Uromyces spp. can be more conspicuous but are much less serious. Pests of white clover in the subtropics are usually of minor importance. Total annual DM yields range from < 1 to > 7 t/ha. Peak DM yields on offer in well grazed pastures seldom exceed 1 t/ha and are more often under 0.5 t/ha. However, as white clover is selectively grazed such yields substantially improve animal production. Good clover growth results in increased soil nitrogen status.

Genetic resources and breeding

Germplasm collections are held in many countries. An important collection is held by DSIR Grasslands Division, Palmerston North, New Zealand. The main breeding programme to improve white clover for use in the subtropics has been carried out in Florida, United States, leading to the release of cultivar "Osceola". There is some evidence that T. repens is an amphidiploid and its related diploid species are thought to be T. nigrescens Viv., a self-incompatible Mediterranean annual, and T. occidentale Coombe, a self-compatible perennial indigenous to southern England, south-western France and Spain.

Prospects

While breeding and selection may improve the persistence and productivity of white clover in tropical highlands and subtropical areas where it is adapted, it is unlikely that breeding will substantially increase its area of adaption.

Literature

• Baker, M.J. & Williams, W.M., 1987. White clover. CAB International, Wallingford, UK. 534 pp.
• Evans A.M., 1976. Clovers. In: Simmonds, N.W. (Editor): Evolution of crop plants. Longman, London. pp. 175-179.
• Gibson, P.B. & Cope, W.A., 1985. White clover. In: Taylor, N.L. (Editor): Clover science and technology. No 25. American Society of Agronomy, Madison, United States. pp. 471-490.
• Jones, R.M., 1984. White clover (Trifolium repens) in subtropical southeast Queensland, III. Increasing clover and animal production by use of lime and flexible stocking rates. Tropical Grasslands 18: 186-192.
• Oram, R.N., 1990. Register of Australian herbage plant cultivars. CSIRO, Australia. pp. 111-117.
• Ostrowski, H., 1972. White clover (Trifolium repens) in subtropical Australia - a review. Tropical Grasslands 6: 97-106.
• Zohary, M. & Heller, D., 1984. The genus Trifolium. The Israel Academy of Sciences and Humanities, Ahva Printing Press, Jerusalem. pp. 167-171.

Authors

R.M. Jones & S.M.M. Kersten