Trifolium burchellianum Ser.

Leguminosae

Synonyms

T. johnstonii Oliv.; T. brasileianum Choiv. Common names. Burchell's clover, Cape clover.

Description

A perennial clover with a variable habit and a strong taproot. Stems glabrous or nearly so, creeping and rooting at the nodes, or, less often, ascending. Leaves glabrous or nearly so, with a well-developed, free petiole. Free parts of the stipule triangular, tapering gradually to the tip, much shorter than the base. Leaflets cuneate-oblong, cuneate-obovate or cuneate-elliptic, less often oblong, emarginate or less often, truncate or rounded at the tips, up to 25 (50) x 19 mm, teeth rather small, main nerves 10 to 15 on each side at about 50° to the midrib. Inflorescence many-flowered, more or less globular, up to 3 cm across. Peduncle longer than the subtending leaf, pilose towards the top. Bracts 0.5 to 2 mm long. Pedicels stout, 2 to 2.5 mm long, more or less erect in fruit, glabrous. Calyx glabrous except for a few hairs at the margin. Tube 11-nerved, 2 to 3 mm long, teeth triangular for about 0.5 mm at the base only, then subulate, in all 4 to 7 mm long. Corolla purple. Standard 8 to 13 mm long. Blade of wings straight, more or less oblong, its auricle less than 0.5 mm long. Ovary glabrous or minutely scabid-punctate, usually two, occasionally three to four ovules. Pods about 5 by 3 mm. One to two seeds, dark brown, irregularly oval, about 2.1 by 1.8 mm (Gillett et al., 1971).

Distribution

There are three subspecies. Ssp. burchellianum, one of only two Trifolium spp. indigenous to Africa, occurs in southern Africa, Lesotho and Angola and has 2n = 48 chromosomes. It is found in lightly grazed, cool, high-altitude sites, in Lesotho up to 3 000 m elevation and in the fringing areas of the Orange Free State, Natal and Cape Province. It also occurs at lower elevations in southern Natal and over a wide range of Cape Province to the fringe of the Karroo, and occasionally into western Cape Province (Jones, Strijdom and Theron, 1974).
Ssp. johnstonii (Oliv.) Gillett has larger flowers and leaflets, and 2n = 96 chromosomes. It occurs in Uganda, Kenya, Tanzania and southern Ethiopia, especially in moist places from 1 800 to 3 700 m elevation with annual rainfall of 1 000 mm and over: upland grasslands, openings in evergreen forests, bamboo forests and moorlands. It is also found occasionally in the alpine zone. Ssp. johnstonii is the most common subspecies in East Africa.
Ssp. oblongum Gillett occurs in Kenya and southern Ethiopia in the undergrowth of forest margins (Gillett, Polhill and Verdcourt, 1971). Less commonly, it occurs in tall grass, where it is more upright.

Rhizobium relationships

Effective nodulation is achieved by Rhizobium strains not suited to European clovers that nodulate at a lower pH, usually above pH 5.5 (Jones, Strijdom and Theron, 1974).

Nutrient requirements

Grows well in low phosphorus soils (Jones, Strijdom and Theron, 1974).

Feeding value

In vitro digestibility can be lower than for T. repens, but is still satisfactory. N content is similar to that of T. repens. In addition, T. burchellianum contains no prussic acid and has a low level of "fraction S" protein, so it should not have a high bloat potential (Jones, Strijdom and Theron, 1974).

General features

T. burchellianum is one of the more promising African species for possible domestication. It is a productive and palatable plant in suitable habitats, with a wide range of ecotypes owing to the wide distribution of the three subspecies. In the future, it will probably yield commercial cultivars. "Notes on Kenya agriculture" (1959) suggests that at least some ecotypes can be shy seeders and slow to establish. A minimum seeding rate of 2 kg./ha was recommended. As the growing points are not restricted to the soil surface, it can tolerate shade better than T. repens, being able to get up to the light to some extent (Jones, Strijdom and Theron, 1974).
The southern African forms appear to have greater ecological tolerance and genetic diversity than T. africanum. They are not as frost tolerant as T. repens and appear more frequently along roadsides than in grazed fields (Jones, Strijdom and Theron, 1974).

Links for the genus:

The true clovers: Exploration, preservation, evaluation and enhancement
Clovers: Cultural specification and management of several species
Insect pollination of clover species: Chapter 3 of the Virtual Beekeeping Book
Sorting Trifolium names: Database of synonymes and common names
Cover crops: Rich information with links to species, references and photographs

Main references

Jones, Strijdom and Theron (1974); Gillett, Polhill and Verdcourt (1971).

Pests and diseases

Red spider (Tetranychus spp.) and root knot nematodes (Meloidogyne spp.) have been the two main pests in artificial cultivations in southern Africa. Rugose leaf curl has also been noted in Australia (Jones, Strijdom and Theron, 1974).

Seed characteristics

Flowering in the field occurs from mid-spring through mid-summer. More than 90 percent of seed set is hard and remains so. There are c. 700 000 seeds/kg. It is cross-pollinating (Jones, Strijdom and Theron, 1974).