Trifolium africanum Ser.

Leguminosae

Synonyms

Lupinaster africanus (Ser.) Ech. and Zey.; Trifolium burchellianum Ser. var. africanum (Ser.) Kuntze.

Common names

Erasmus clover.

Description

A perennial legume with stems mainly prostrate, rooting at the nodes of the lateral runners, pilose. Var. africanum has petioles usually free for more than 1 cm, although sometimes less than 1 cm in the upper leaves. Leaflets obovate to elliptic, ranging from less than twice as long as wide to between twice and four times as long as wide, pilose on both surfaces, apex acute, rounded emarginate. Inflorescences with many purple flowers, globose, about 2 cm wide. Peduncle up to 12 cm long. Pedicels pilose, erect after flowering. Calyx pilose with less than 15 nerves. Var. glabellum (E. Mey.) Harv. has glabrous leaflets and glabrous stems, while var. lydenbergense (Gillett) has glabrous stems and linear-lanceolate leaflets that are glabrous above and sometimes sparsely pilose below. The apex is acute, rounded or slightly emarginate, and is more than five times longer than wide ('t Mannetje, 1966).

Distribution

T. africanum and T. burchellianum are the only two Trifolium species indigenous to southern Africa. T. africanum var. africanum is mainly confined to the Witwatersrand and the eastern Transvaal highveld, that part of Natal above 500 m elevation and 750 mm rainfall, Lesotho, and adjacent areas of the Orange Free State and Cape Province. Var. glabrellum has a similar distribution but is more frequent in Natal and less frequent in the Transvaal, while var. lydenbergense is confined to the eastern Transvaal highveld, where the rainfall is about 750 mm (Jones, Strijdom and Theron, 1974) .

Rhizobium relationships

T. africanum nodulates effectively with rhizobia not effective on European clovers. In addition, it nodulates at lower pH levels, although usually above pH 5.5, and nodulates and fixes nitrogen at higher temperatures than T. pratense and T. repens. It tolerates root temperatures of up to 40°C compared with 26 to 33°C for T. pratense and T. repens (Jones, Strijdom and Theron, 1974).

Nutrient requirements

T. africanum has been observed growing well on low-phosphate soils (Jones, Strijdom and Theron, 1974).
On acidic, P-fixing soils, T. africanum outyielded T. repens. Elimination of exchangeable aluminium from the soil by the use of lime significantly increased the yield of both species. T. africanum had twice the Ca content of T. repens on the limed soil. Lime also improved the ability of T. africanum to extract P from the soil (Hackland, Booysen and Somner, 1976).

Toxicity

T. africanum contains no prussic acid.

General features

All areas of occurrence have summer-dominant rainfall and most frost in winter, some receiving isolated snowfalls. T. africanum occurs mostly in lightly grazed, cool, moist, high-altitude sites. At lower altitudes or lower rainfalls (to 650 mm), it occurs only in wet sites or on river banks (Jones, Strijdom and Theron, 1974). It appears that T. africanum occurs more widely on roadsides than in grazed veld and that it survives regular close mowing. T. africanum is adapted to acidic, highveld soils and is frost hardy, though not as hardy as T. repens (Jones, Strijdom and Theron, 1974).
As in the case of T. semipilosum, the growing points of the stolons are not confined to the soil surface, so that they can climb up to combat overshading to a greater extent than those of white clover. Swards develop numerous, small taproots connected by both surface and subsurface stolons (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 (1952).

Pests and diseases

Red spider (Tetranychus spp.) and root knot nematode (Meloidogyne spp . ) have been the main pests in cultivated stands but there are variations in reaction to them (Jones, Strijdom and Theron, 1974).

Seed characteristics

T. africanum flowers from mid-spring to mid-summer. More than 90 percent of seed set is hard. There are about 700 000 seed/kg. (range 450 000 to 1 100 000). It is cross-pollinating. The chromosome number is 2n = 32 for var. africanum (Jones, Strijdom and Theron, 1974).