Indigofera lyalli

Baker subsp. lyalli

Family : Fabaceae (pea family)
Common names : Red indigo, Venda indigo; rooiverfbos, Venda-verfbos (Afr.); Umhlonishwa (isiZulu)

Inflorescence

 

An attractive, delicate-looking, slender tree with velvety leaves and wine-red flowers usually found growing in clusters in nature.

Description
An evergreen woody plant that can be grown as a shrub, 2–3 m in height or, in favourable conditions, as a lovely small tree up to 5–6 m in height with a trunk diameter of no more than 150 mm. Compound leaves, dark green above and pale green below; 8–12 pairs of squarely oblong leaflets and a terminal leaflet all covered in soft, flexible hairs giving them a velvety texture and appearance. Young shoot tips are furled and velvety brown; young twigs are also densely velvety. Flowers coloured a deep wine-red, 50 mm long occurring in short compact racemes. They appear in autumn, from March to April, and occasionally occur throughout the year. Fruits are distinctive small cylindrical reddish brown pods, about 0.3 mm, which split and twist open when mature and usually hang ‘dripping' from the plant from May to October.

Leaves and pods

Conservation status
Indigofera lyalli subsp. lyalli is Red-Listed as of LC (Least Concern) and is therefore at low risk of extinction.

Distribution and habitat
Indigofera lyalli subsp. lyalli is found the Soutpansberg in Limpopo Province at ± 450–2 300 m altitude on rocky slopes, in open woodland or thicket. Its distribution range also includes parts of Gauteng, Eastern Cape, Cape Province and even Botswana, mainly growing along forest margins, forested ravines and river banks in mountainous areas and sometimes on open grassy mountain slopes in more protected areas within montane grassland. Plants often occur in groups.

Derivation of name and historical aspects
The genus Indigofera is composed of ‘indigo' referring to the colour, and ‘fero' meaning ‘to bear'. The species name lyalli is of unclear origin, possibly named after Robert Lyall (1790–1831), a Scottish botanist and collector in Madagascar where the type specimen was collected. Another possibility is that it was named after David Lyall (1817–1895), another plant collector in Madagascar.

Indigofera is a large genus of over 800 species common to tropical and subtropical regions, mostly herbs and under-shrubs, with two tree-like species. More than 200 species are widespread in southern Africa,

This genus is classified under the legume or pea family, Fabaceae. Members of the pea family are fairly diverse and include economically important crops such as beans, peas and clover, as well as herbs, shrubs and a few beautiful flowering trees. The characteristic sweet-pea flowers of this family have a large upper petal (the standard), two side petals (wings) and two lower petals that are fused to form a ‘keel' enfolding the stamens and pistil.

Other noteworthy members of this genus are:

  • Indigofera jucunda , a shrub or small, graceful tree (4–7 m). It also has grey bark and leaves that are dark green and compound with leaflets, but in this plant they are arranged in pairs of 4–7 with a terminal one. Flowers are small, pinkish white and sweetly scented. They are borne from December through to April in clusters on lovely, dainty spikes. Similar smooth, reddish brown, cylindrical pods appear from May to July.
  • Indigofera natalensis, a shrub or slender tree up to 1–3 m with pale grey bark. The leaves are shiny, dark green and compound – they are composed of one to two pairs of leaflets and a terminal leaflet with a drip tip . The flowers are small, white occasionally tinged with mauve, and borne on short delicate sprays from December to March. The fruits appear from May to June and are cylindrical red-brown pods.

Ecology
Several species of butterflies including the common Lucerne Blue ( Lampides boeticus ) and the Drakensberg Blue ( Lepidochrysops niobe ) breed on members of the genus.

Uses and cultural aspects
The name ‘indigo' refers to the dye that is obtained from several species of the genus . It gives a light purple to mauve colour or sometimes dark brown or grey, depending on the dyeing time. The leaves of some Indigofera species are the main source of the dye but sometimes the roots are also used. Formerly important, they have now mostly been replaced by aniline dyes. Some species are still grown for use as green manure and fodder. The wood of Indigofera natalensis is used for fuel and for fence supports. Other species of Indigofera have medicinal uses, such as helping with infertility and menstrual cramps. One is even believed to be able to change the sex of a baby before birth. Another species' twigs are used as toothbrushes and its sap used as mouthwash.

A few species are grown as horticultural ornamentals and make for pretty and neat garden subjects.

Shrub with seed pods.

Growing Indigofera lyalli subsp. lyalli

Indigofera lyalli subsp. lyalli is dainty and showy when in flower and seed, making it an interesting garden subject.

Indigofera lyalli subsp. lyalli prefers a warm, sunny position in the garden although it will tolerate shade for some part of the day. It grows easily in good, loamy soil. Plant trees as single specimens, or in small odd-numbered groups . Given a thick regular layer of compost mulch, it will grow well and be even more tolerant of a wide range of temperatures.

Indigofera lyalli subsp. lyalli plants are naturally neat, and so require little or no pruning, if it is necessary to do a little trimming/shaping then do it in late winter after the plant has finished flowering.

As with most Fabaceae, propagating Indigofera lyalli subsp. lyalli is quite difficult from cuttings, so it is best grown from seed. Seeds of this species quickly disperse and the seed pods are often parasitised. Pods also split open without warning and disperse the seed with force, so gather the pods early or tie a stocking around the stem of ripening pods to catch the seeds.

The seeds germinate easily. Sow them in autumn or spring, in a well-drained soil mix and cover lightly with the sowing medium. Prior to sowing, soak the seeds in warm water and leave overnight to improve germination. To prevent pre- and post-emergence damping off, the seed should be treated with a fungicide when sowing. Transplant the seedlings after the first pair of true leaves have emerged. Feed moderately with a liquid fertiliser and water generously. When large enough, plant the young trees into a permanent location in full sun or semi-shade. They need good, light soil and average watering, particularly during their first two to four years. This plant's growth rate is medium to fast and flowering can expect to occur within 3–4 years.

References and further reading

  • Coates Palgrave K. (Revised and updated by Meg Coates Palgrave). Trees of Southern Africa , 3rd edition 1977. Struik, Cape Town.
  • Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa , Ed 3 . Struik,
  • Dyer, R.A., Verdoorn, I.C. & Codd, L.E. 1962. Wild Flowers of the Transvaal. Wild flowers of the Transvaal Book Fund.
  • Germishuizen, G. & Meyer, N.L. (eds). 2003. Plants of southern Africa: an annotated checklist. Strelitzia 14. National Botanical Institute, Pretoria.
  • Hyam, R. & Pankhurst, R. 1995. Plants and their names A concise dictionary . Oxford University Press, .
  • Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
  • Roger Hyam & Richard Pankhurst. 1995. Plants and Their Names, Oxford University Press, United States.
  • Van Wyk, A.E. & Van Wyk, P. 1997. Field guide to trees of southern Africa . Struik, Cape Town.

 

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