Crotalaria magaliesbergensis

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Crotalaria magaliesbergensis A.S.Flores & Sch.Rodr.

Family: Fabaceae

Common names: Magaliesberg rattlepod (Eng.); magaliesberg jaagsiektebossie (Afr.)

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Introduction

Crotalaria magaliesbergensis is small shrub that sprouts annually from a woody rootstock, to produce many, fragrant, yellow flowers. It will be a great addition to any indigenous garden in the Highveld region, best suited in rocky gardens or en masse in open beds.

Close-up of the inflorescence showing a few flowers of Crotalaria magaliesbergensis.

Figure 1. Close-up of the inflorescence showing a few flowers of Crotalaria magaliesbergensis.

Description

A neat, rounded, perennial shrublet, 0.2–0.5 m tall and 0.24–0.47 m in diameter, re-sprouting annually from a woody rootstock with numerous, erect (sometimes branching) stems, which are covered in fine silky white hairs (under magnification) that seem hairless to the naked eye.

Two plants of Crotalaria magaliesbergensis in habitat.

Figure 2. Two plants of Crotalaria magaliesbergensis in habitat.

Base of a plant of Crotalaria magaliesbergensis showing the woody rootstock.

Figure 3. Base of a plant of Crotalaria magaliesbergensis showing the woody rootstock.

The leaves are compound, stalked and trifoliolate, with the leaflets obovate.

Branch of Crotalaria magaliesbergensis showing leaves consisting of 3 leaflets each.

Figure 4. Branch of Crotalaria magaliesbergensis showing leaves consisting of 3 leaflets each.

Flowers are carried in terminal racemes that are 50–100 mm long and carry 16–25 flowers. The flowers are bright canary yellow with the keel angular, to form a long, blunt beak.

Raceme with flowers of Crotalaria magaliesbergensis.

Figure 5. Raceme with flowers of Crotalaria magaliesbergensis..

The fruits are inflated, globose (round) pods (± the size of a pea) and contain a hard exocarp, covered with minute silky hairs and the remains of the keels as the fruits mature, and contain 2–4 seeds.

Fruit of Crotalaria magaliesbergensis. A, two racemes with numerous fruit each. B, close-up.

Figure 6. Fruit of Crotalaria magaliesbergensis. A, two racemes with numerous fruits each. B, close-up.

Fruit and seed of Crotalaria magaliesbergensis. A, rugose (hairy) fruit viewed from outside. B, dissected fruit showing the young seed inside. C, young seed in side view.

Figure 7. Fruit and seed of Crotalaria magaliesbergensis. A, rugose (hairy) fruit viewed from outside. B, dissected fruit showing the young seed inside. C, young seed in side view.

Flowering time varies from October to March, depending on rainfall. A few unusual collections from May and September have also been recorded. It is a very hardy plant and a fast grower.

Conservation Status

Status

The magaliesberg jaagsiektebossie is widespread and common and despite its decline in Gauteng because of loss of habitat to urban development and agriculture, the species is currently not at threat of becoming extinct and thus has a conservation assessment of Least Concern (LC).

Stand of Crotalaria magaliesbergensis along roadside in Doornpoort, Pretoria.

Figure 8. Stand of Crotalaria magaliesbergensis along a roadside in Doornpoort, Pretoria.

Distribution and habitat

Distribution description

Plants are found growing in grassland and bushveld (savanna or open woodland), often in moist places and along roadsides.

Crotalaria magaliesbergensis has been recorded from the four Northern Provinces in South Africa (North-West, Limpopo, Gauteng and Mpumalanga) notably on the Magaliesberg, Waterberg and Soutpansberg ranges, as well as from the northern Free State and Zimbabwe. It grows at altitudes ranging from 610–1 637 m above sea level.

Plants have been recorded from granite, sandstone and shale geology. Plants exclusively grow in full sun in grassland, open woodland, sometimes roadsides, in stony to rocky, gravel, sandy, and sandy-loam or loamy-clay soils, in both plains and on hill and mountain slopes.

Distribution of Crotalaria magaliesbergensis based on records at the National Herbarium (PRE) in Pretoria.

Figure 9. Distribution of Crotalaria magaliesbergensis based on records at the National Herbarium (PRE) in Pretoria.

Derivation of name and historical aspects

History

The generic name is derived from the Greek word krotalon, meaning 'castanet' or 'rattle', which refers to the sound made by the seeds in the mature capsules of many species. Interesting is that this same Greek word is the same base used for the word translating to ‘rattlesnake’. The epithet of the former name brachycarpa is also Greek and refers to the ‘short fruit’. This name was, however, already used for another species growing in Brazil and because of priority rules, the epithet was changed to ‘magaliesbergensis’, which refers to the mountain range stretching more or less from Pretoria to Rustenburg. This name was chosen as the type of this plant, as it comes from the Magaliesberg. Joseph Burke collected the type specimen on the Magaliesberg between May–August 1841, presumably closer to Rustenburg than Pretoria.

The genus consist of over 600 species that are cosmopolitan in the tropics and extend to the subtropics, especially southern Africa, where at least 64 species have been recorded (Leistner 2000). The outstanding characters for the genus Crotalaria, is the pointed keel formed by the lowermost 2 petals and the inflated fruit. Polhill in 1982, placed C. magaliesbergensis in the section Crotalaria and subsection Longirostre mainly because of the keel bent at right-angles in the lower half, with a narrow, ± straight beak. The style is further geniculate and constricted in the bend of the keel. The outstanding characters for C. magaliesbergensis are the trifoliolate leaves and numerous stems sprouting from a woody rootstock.

The flower of Crotalaria magaliesbergensis shown from different angles to different petals namely standard (1 enlarged petal), wings (two petals in the middle) and keel (2 lowermost, reduced petals).

Figure 10. The flower of Crotalaria magaliesbergensis shown from different angles to different petals namely standard (1 enlarged petal), wings (two petals in the middle) and keel (2 lowermost, reduced petals).

Crotalaria magaliesbergensis is closely related in morphological characters to C. globifera (Polhill 1982;Pooley 2005) from which it differs in having a rugose, spherical fruit, 5–7 mm long, opposed to glabrous, obliquely obovoid or oblong-obovoid, 7–13 mm long fruit in the latter; is 2–4-seeded, instead of 4–6-seeded as in C. globifera; and the standard is glabrous outside (opposed to being pubescent outside – at least medially but mostly extensive); and having the bracts deciduous after flowering (bracts persistent in C. globifera).

On the plains of red soil north of the Magaliesberg (Pretoria area), Crotalaria magaliesbergensis shares its habitat with the spiny C. eremicola, one of a few other members of the genus growing in the area.

Crotalaria cousins growing in the same area. A, Crotalaria magaliesbergensis. B, Crotalaria eremicola.

Figure 11. Crotalaria cousins growing in the same area. A, Crotalaria magaliesbergensis. B, Crotalaria eremicola.

Ecology

This jaagsiektebossie is adapted to the harsh environment of the Highveld. It is a hardy plant and will do well in many other areas as it adapts to both wet and dry areas easily.

In its natural distribution range, this species grow in areas with harsh winters and dies back in late summer after fruiting. Plants are thus well-adapted to their environment and become dormant as underground rootstocks during the unfavourable time of the year. This mechanism is utilised not only to survive the cold, but also wild fires at the end of winter. In early spring adventitious buds on the rootstock are stimulated by an increase in temperature (or due to fires) to resprout.

In contrast to C. capensis which is pollinated by carpenter bees, only honey bees have been observed to pollinate C. magaliesbergensis. Almost no other literature exists on the biology of this specific species, which needs to be investigated further.

This species falls in a group of species of Crotalaria that have small, few-seeded, spherical, indehiscent fruits that appear to be adapted to wind, water or gravity dispersal perhaps with a rolling action (Le Roux et al. 2011).

On the label of one specimen, it has been recorded that the root forms root nodules. These nodules are generally formed by bacteria that live symbiotically with the plant and helps in the fixing of free nitrogen – one of the reasons that many Crotalaria species are used to fertilize soils in preparation for growing other crops.

Uses

Use

The genus has been reported to have many uses, that include being used as fibre crops, fodder and green manure, medicines, ornamentals, nurse crops, heavy metal indicators, used in human food and soil improvement (intercropping); some cause chronic poisoning of both humans and livestock, affecting the lungs and liver. C. juncea (Sunn hemp), is a major crop utilised for its bark which provide high quality fibres for cords and ropes, fishing nets and fine paper (POWO, 2018).

Many species of Crotalaria in southern and eastern Africa cause disease of the liver and lungs in wild game, donkeys, horses and oxen. Some are used medicinally, other as fodder crops.

Pyrrolizidine alkaloids from Crotalaria have been indicated to cause chronic poisoning of livestock. It is, however, not established if the current species is also included. Plants containing these alkaloids are, however, rarely reported to be responsible for poisoning in humans. In cases where Crotalaria have been used for traditional medicine, it has been responsible for chronic intoxication, causing abdominal pain, loss of appetite and oedema of the extremities.

Van Wyk and others (2002) points out that members of Crotalaria is responsible for at least 3 types of poisoning in livestock. Jaagsiekte that is associated with C. juncea, C. dura and C. globifera (the last 2 very similar to C. magaliesbergensis in appearance) and the ingestion of large quantities of these plants (or ingestion over a long period) result in a condition known as crotalariosis and cause serious liver and lung damage, eventually leading to the death of animals.

Crotalaria magaliesbergensis although similar and occurring with C. dura and C. globifera, is (as far as could be established), not poisonous to livestock. The roots of the former 2 species are known to be used in traditional medicine.

As with most Crotalaria, this plant will definitely attract bees and possibly also butterflies and secondary birds feeding on the insects. A number of Crotalaria species are used as food plants throughout Africa by the larvae of the moth Endoclita sericeus.

Growing Crotalaria magaliesbergensis

Grow

It can be classified as a half-hardy plant that requires moderate watering and full sun growing conditions.The magaliesberg jaagsiektebossie is indeed a plant that would be rewarding when cultivated in a garden. The only other members of the genus that have been covered in this series are C. capensis and C. natalitia var. natalitia, and perhaps growing these quite different species together, may make good displays. It could be inter-planted with shorter grass species to attain a natural feel in a garden. Because C. magaliesbergensis being a quite compact bush, it may also be well-suited as container plant in small gardens or on patios.

Plants are best grown from seed. The best time to harvest seed are when the fruit turn yellow, just before they detach from the plant. Place the fruit in a brown paper bag and store it in a dry and cool place until the next season. The seed needs to mature and overwinter, otherwise it will not germinate. Johan Wentzel from wildflowernursery.co.za has successfully grown Crotalaria magaliesbergensis. The method he used was to sand the seed coat with fine sanding paper on one small patch until the cotyledons are just visible. The seed are then soaked overnight by pouring hot water (from a geyser) on them. It is ready to be sown the next morning in a seeding tray. Put the seeds on top of a mixture of 1:1 commercial seedling soil and fine unwashed river sand. Then lightly cover the seeds with a layer of unwashed river sand. Keep the tray damp by watering in the mornings. It takes between 5–10 days to germinate. Best time to sow the seed is spring to early summer. In the wild plants usually drop their fruit in mid-summer and it probably takes at least until the next year for the fruit to degrade to such an extent that water can penetrate the fruit/seed.

References

Flores, A.S. & Rodrigues, R.A. 2011. Crotalaria magaliesbergensis, a new name for Crotalaria brachycarpa from South Africa (Leguminosae). Phytotaxa 33: 59.
Germishuizen, G. & Fabian, A. 1997. Wild flowers of northern South Africa. Fernwood Press, Vlaeberg, Cape Town.
Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
Mnxati, S. 2012. Crotalaria natalitia var. natalitia. PlantZAfrica. http:/pza.sanbi.org/crotalaria-natalitia-var-natalitia.
Polhill, R.M. 1982. Crotalaria in Africa and Madagascar. A.A. Balkema, Rotterdam.
Pooley, E. 2005. A field guide to wild flowers KwaZulu-Natal and the eastern regions. The Flora Publications Trust, Durban.
Verdoorn, I.C. 1928. A revision of the crotalarias of South and South-East-Tropical Africa. Bothalia 2: 371–420.
Van Wyk, B. & Malan, S. 1997. Field guide to the wild flowers of the Highveld. Struik Publishers, Cape Town.
Van Wyk, B.-E., Van Heerden, F. & Van Oudtshoorn B. 2002. Poisonous plants of South Africa. Briza Publications, Pretoria.
Vahrmeijer, J. 1981. Poisonous plants of southern Africa that causes stock losses. Tafelberg publishers, Cape Town.
Viljoen, C. 2007. Crotalaria capensis. PlantZAfrica. http:/pza.sanbi.org/crotalaria-capensis.
Von Staden, L. 2011. Crotalaria magaliesbergensis A.S.Flores & Sch.Rodr. National Assessment: Red List of South African plants version 2017.1. Accessed on 2018/11/26.