Tephrosia zoutpansbergensis
Introduction
Tephrosia zoutpansbergensis is a bushy shrub that belongs in the Fabaceae (legume family), with yellowish orange flowers in spring and summer followed by brown pods. It is an adaptable, drough-tolerant plant. Its nitrogen-fixing roots, and flowers and fruits that feed a variety of wildlife make it a valuable component in the ecosystem, although the plant contains toxic compounds that can be harmful to animals and people when eaten.
Description
Description
Tephrosia zoutpansbergensis is a perennial, nitrogen-fixing shrub. It typically grows to a height of 1–2 m, with a spread ranging from 1–1.5 m. This plant exhibits a bushy growth habit, with multiple stems arising from a deep-rooted, woody base. Young stems are densely covered with silvery silky hairs. The root system features a robust taproot that allows it to access moisture and nutrients from deeper soil layers, making it well-adapted to arid conditions. The leaves of Tephrosia zoutpansbergensis are compound and pinnate, composed of 2-4 pairs of small leaflets arranged along a central axis, the upper surface is hairless and the lower surface is covered in short soft hairs pressed closely to the leaf. The foliage is a medium green colour, providing an appealing contrast against the bright shades of yellow and orange of the flowers. These flowers, which are characteristic of the Fabaceae family, are borne in racemes at the tips of the stems, and have a typical pea-like structure, with a prominent standard petal, two wing petals, and fused keel petals. The vibrant colour of the flowers serves as a strong attractant for pollinators, including bees and butterflies.
Flowering occurs primarily in the warmer months, from early spring to late summer, though some plants may continue to bloom sporadically into autumn, depending on environmental conditions. Following the flowering period, the plant produces slender, ovoid or oblong pods containing several seeds. These pods are densely covered with short hairs, and start off green but mature to a brownish or greyish hue as they dry, eventually splitting open to release seeds for dispersal. The seeds are small, oval, and hard-coated, allowing them to persist in the soil for extended periods until germination conditions become favourable.
Conservation Status
Status
According to the SANBI Red List of South African Plants, Tephrosia zoutpansbergensis is listed as a species of Least Concern (LC). This taxon was not selected in any one of the SANBI Red List screening processes for detailed assessment and was hence given an automated status of Least Concern. This species has a low population density, and plants are not often seen or nor have many herbarium specimens been collected. A thorough asessment may amend the Red List status to Rare.
Distribution and habitat
Distribution description
Tephrosia zoutpansbergensis is occurs in Zimbabwe, Botswana and South Africa. In South Africa, it is found on the Soutpansberg mountain range, in Limpopo. This area is characterized by rocky outcrops, well-draining soils and a semi-arid climate, making it an ideal habitat for drought-tolerant species. The plant is commonly found growing in open grassland, woodland edges and along disturbed areas where its nitrogen-fixing ability plays a crucial role in soil restoration.
This species prefers full sun to partial shade and thrives in sandy or loamy soils with a pH range between 6.0 and 7.5. It has evolved to withstand dry periods by utilizing its deep root system to access groundwater reserves. Due to its adaptability, Tephrosia zoutpansbergensis can also be found in areas with seasonal rainfall, where it takes advantage of periodic moisture availability to grow and reproduce.
Derivation of name and historical aspects
History
The genus name Tephrosia is derived from the Greek word tephros, meaning ‘ash-coloured’, referring to the often greyish or silvery appearance of the foliage in some species. The species name zoutpansbergensis is a geographical reference to the Soutpansberg mountain range in Limpopo, South Africa, where the plant was first documented.
Tephrosia is a diverse genus within the Fabaceae (legume family), comprising about 400 species distributed across tropical and subtropical regions worldwide. Many species within this genus are utilized for their insecticidal properties, soil-enriching capabilities and medicinal applications.
The Fabaceae is one of the largest families of flowering plants and is crucial for ecological functions such as nitrogen fixation and providing food sources for various animals and insects, and humans.
Ecology
Ecology
As a nitrogen-fixing legume, Tephrosia zoutpansbergensis plays a vital ecological role by improving soil fertility. It forms symbiotic relationships with Rhizobium bacteria, which convert atmospheric nitrogen into a form that plants can absorb, enriching the surrounding soil and benefiting neighbouring vegetation.
This species is highly attractive to pollinators, particularly bees and butterflies, which are drawn to its bright yellow flowers. By providing nectar and pollen resources, the plant supports local insect populations and contributes to biodiversity conservation. Additionally, its deep root system helps prevent soil erosion, particularly in disturbed or degraded landscapes.
Despite its ecological benefits, Tephrosia zoutpansbergensis contains toxic compounds that can be harmful to humans and animals if ingested. These compounds, primarily rotenoids, have been historically used in natural pesticides and fish poisons. While the plant's toxicity deters herbivory from larger animals, certain insects have adapted to feed on its foliage without adverse effects.
Uses
Use
Traditionally, various Tephrosia species have been used in African and Asian cultures for medicinal and agricultural purposes. Tephrosia zoutpansbergensis, like its relatives, has potential applications in soil improvement, erosion control, and as a source of natural pesticides. The rotenoids present in the plant are known for their insecticidal properties, and extracts from some Tephrosia species have been used to control agricultural pests.
Despite its toxicity, the plant has been used in traditional medicinal practices, mainly by the Venda people, who are found in this region of Limpopo, with careful processing to mitigate harmful effects. However, its use in modern herbal medicine is limited due to the risks associated with its toxic compounds. This species is used to treat male health issues such as weak erection and to increase libido.
Growing Tephrosia zoutpansbergensis
Grow
Tephrosia zoutpansbergensis can be propagated through both seeds and cuttings. Seed propagation is the most common method, as the seeds are relatively easy to collect and store. However, they possess a hard seed coat, which can delay germination. To improve germination rates, seeds should be scarified by soaking them in warm water for 24 hours before planting. Ideal germination temperatures range between 20-25°C with seedlings typically emerging within 7-14 days.
Propagation through cuttings is another viable option. Cuttings about 10-15 cm long should be taken from healthy, mature plants during the growing season (spring to early summer). These cuttings should be treated with a rooting hormone and placed in well-draining soil, where they will develop roots over several weeks.
To successfully cultivate Tephrosia zoutpansbergensis, it is essential to choose a planting site with full sun to partial shade and well-draining soil. Overly wet conditions should be avoided, as waterlogged soil can lead to root rot.
When planting from seeds, they should be sown about 5 mm deep and spaced 0.5–1 m apart to allow sufficient room for growth. Initial watering should be regular until the plants establish themselves, after which irrigation can be reduced due to their drought tolerance. Drip irrigation is recommended to prevent excess moisture on foliage, which can lead to fungal infections.
Fertilization should be done every 4-6 weeks during the growing season, using a balanced NPK fertilizer to support healthy development. However, excessive nitrogen supplementation is unnecessary due to the plant’s nitrogen-fixing ability.
Pruning can help maintain a bushy and compact growth habit. It is best to prune after flowering to encourage new growth and remove any dead or damaged stems.
Regular monitoring for pests and diseases is essential, although Tephrosia zoutpansbergensis is generally resilient. Common issues include root rot from overwatering, spider mites and mealybugs, which can be managed through appropriate cultural practices and organic treatments.
References
- Brummitt, R.K. & Harder, D.K. 2007. Leguminosae - Papilionoideae. Flora Zambesiaca 3(3). Royal Botanic Gardens, Kew, London.
- Codd, L.E.W., Dyer, R.A., Rycroft, H.B. & Winter, B.D. 1963. Flora of Southern Africa: the Republic of South Africa, Basutoland, Swaziland and South West Africa. Government Printer. Pretoria.
- Forbes, H.M.L. 1948. A revision of the South African species of the genus Tephrosia Pers. Bothalia 4(4):951-1001.
- Kalwij, J. 2022. Observation of Tephrosia zoutpansbergensis, Waterberg Mountain. iNaturalist. Online. https://www.inaturalist.org/observations/104648336.
- McKenzie, D. 2025. Observation of Tephrosia zoutpansbergensis, Mopani District. iNaturalist. Online. https://www.inaturalist.org/observations/261520245.
- Palmer, E. & Pitman, N. 1972. Trees of southern Africa. Balkema, Cape Town.
- Van der Merwe, T. 2025. Observations of Tephrosia zoutpansbergensis. iNaturalist. Online. https://www.inaturalist.org/observations?taxon_id=595192&user_id=troos.
- Watt, J.M. & Breyer-Brandwijk, M.G. 1962. The medicinal and poisonous plants of southern and eastern Africa , edn 2. Livingstone, Edinburgh & London.
Credits
Mpho Mathalauga
Pretoria National Botanical Garden
March 2025
Acknowledgements: the author thanks Troos van der Merwe, Jesse Kalwij and Duncan McKenzie for the images.
Plant Attributes:
Plant Type: Shrub
SA Distribution: Limpopo
Soil type: Sandy, Loam
Flowering season: Spring, Early Summer, Late Summer
PH: Acid, Neutral
Flower colour: Yellow, Orange
Aspect: Full Sun, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Average
Special Features:
Attracts butterflies
Drought resistant
Poisonous
Medical plant
Feeds honeybees
Horticultural zones
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