PlantLife Volume 59.5, July 2025. Ceropegia sideralis, a new species of Ceropegia from the Western Cape

 

Ceropegia sideralis (Apocynaceae), a new species of Ceropegia sect. Chamaesiphon from the Western Cape, South Africa

By Ralph Peckover

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A new species of Ceropegia (formerly Brachystelma) is described. Photos as indicated.

This article was originally published in CactusWorld: Peckover, R (2024) Ceropegia sideralis (Apocynaceae), a new species of Ceropegia sect. Chamaesiphon from the Western Cape, South Africa, CactusWorld 42(3): 241-245. Permission to republish this article is gratefully acknowledged.

 

Introduction

During October 2021, Sally Hey and Susan Armstrong conducted a botanical survey on a farm near Graafwater, Western Cape, South Africa. The purpose was to record all the plant species in an unusual vegetation type, namely a mixture of fynbos and renosterveld. Whilst collecting plants in the area, a distinctive member of Ceropegia that did not match any of the known species was encountered. It was flowering in full sun and growing in stony, clayey soil. A herbarium specimen of the plant was taken and deposited in the Compton Herbarium (NBG), Cape Town. Later, in mid-December, the plant was found in fruit. The purpose of the present contribution is to describe this Ceropegia from Graafwater as a new species, Ceropegia sideralis. It is provisionally placed in Ceropegia sect. Chamaesiphon, the members of which were historically treated (and still are by many end-users of plant names) in the genus Brachystelma (Dyer, 1983, Bruyns et al., 2017).

The Graafwater area was visited by Sally Hey and Susan Armstrong for three consecutive years to complete the botanical survey and it was noted that flowering of this species of Ceropegia occurred from October onwards depending on when the winter rains arrived (Sally Hey and Susan Armstrong, pers. comm.). For the area surveyed, a total of 337 plant species were recorded, a number which is not unusual for the species-rich[1] fynbos region of the Western Cape. From photos taken at the time, the plants of C. sideralis were associated with members of the Restionaceae (restios), one of the three plant families characteristic of fynbos, the other two being the Proteaceae (proteas) and the Ericaceae (heaths). Around Graafwater, rooibos tea (Aspalathus linearis) is extensively grown commercially and this has led to large areas of fynbos having been cleared to make way for this crop.

 

Fig. 1 C. sideralis with wavy leaves, growing in stony soil similar to the habitat of the related C. occidens from Bredasdorp (Photo: Mike Picker)

In the winter rainfall area of the Western Cape, there are few indigenous ceropegias. One of the first to be described was Brachystelma caudatum (now Ceropegia spathulata) in 1878. It was originally collected near Cape Town by Carl Pehr (Peter) Thunberg (1743–1828) and later also collected near Simon’s Town. In 1893, another species, B. occidentale (now Ceropegia occidens), was discovered near Smitswinkel Bay, Simon’s Town, by Friedrich Richard Rudolf Schlechter (1872–1925). This species grows in stony soil.

During a visit to Bredasdorp in March 1997, the author walked along a temporary stream just outside the town and observed a very small Brachystelma also growing in stony soil on the stream bank. When the plant flowered, it was identified as B. occidentale, a species that since its original discovery was never found again around Cape Town.

The new species from Graafwater shows affinities with the plant from Bredasdorp in both having mostly linear wavy-edged leaves around 30×2mm with the flowers being clustered at the stem nodes. The corolla lobes of both species are also similar in colour, but in Ceropegia occidens they are only 3mm long, incurved, with the lower half whitish and the tips green. The corolla lobes of C. sideralis also have a whitish base but distally the lobes are yellowish to green, up to 8mm long, and laterally reflexed (margins rolled under) to form a tube.

Fig. 2  C. occidens in habitat near Bredasdorp. Since the photo was taken, the natural vegetation of the area has been destroyed. (Photo: Ralph Peckover)

There are also differences in the corona morphology of the two species. The outer corona lobes of C. occidens lie completely on top and cover the inner lobes whilst in C. sideralis they only partially cover the inner lobes. Illustrations as well as a comparative table with morphological features to distinguish between the two species are provided (Figs. 1–10 and Table 1).

Fig. 3  Details of a flower of C. sideralis (Photo: Mike Picker)

Ceropegia sideralis is a relatively small, range-restricted species, and as far as is known, confined to the areas around Graafwater in the Western Cape. Compared to C. occidens, it is a much larger multi-stemmed plant about 130mm tall, with corolla lobes longer, more flowers per leaf axil, flowers considerably larger, and the corolla lobes rolled-under lengthwise as well as notable differences in the corona morphology. The genus Brachystelma, with around 116 recognised species, was sunk under several sections of Ceropegia by Bruyns et al. (2017). Brachystelma occidentale, to which C. sideralis is morphologically most similar, was transferred under the new name C. occidens to Ceropegia sect. Chamaesiphon, the section in which C. sideralis is provisionally placed. Members of sect. Chamaesiphon are confined mostly to southern Africa (around two thirds of the species) with the rest ranging into Africa but also to India and a single species in Australia. All the species of sect. Chamaesiphon have a perennial swollen underground caudex. The stems are deciduous and die back to the caudex at the end of the growing season.

Fig. 4  Close-up of C. occidens flower showing short incurved corolla lobes (Photo: Ralph Peckover)

Fig. 5  Flower of C. sideralis showing the purplish corona, which varies from pinkish to purple (Photo: Mike Picker)

Fig. 6  Corona of C. sideralis showing the upright outer lobes of nectrar pouches and the almost transparent lobes on top of the green inner lobe (photo: Mike Picker)

Members of Ceropegia sect. Chamaesiphon are characterised by leaves that are opposite, linear to elongated, with wavy, sinuate to plane entire margins. These are bright green to greyish and glabrous to very hairy. The flowers are borne in the axils of the leaves or terminally in panicles. Each flower has five corolla lobes, which can be united at their tips or free.

The corona contains the pollinia as well in the gynostegium. The paired follicles develop after fertilisation and may be upright or decumbent and slender or very swollen. When mature these fruits split longitudinally to release the tufted seed which are dispersed by the wind. There may be from a few seeds to many in each follicle. The caudices (tubers) of some species of this group have formerly been used as food by humans, especially by the Bushmen (personal interviews with Bushmen; Dyer 1983).

Fig. 7  The starry flowers of C. sideralis, hence the choice of the specific epithet. The plant was among restios and other fynbos plants (Photo: Mike Picker)

Description

Perennial herb up to 130mm high, erect, usually multi-stemmed, the basal organ a below-ground caudex (tuber), up to 70mm in diameter and 50mm thick, with numerous fusiform roots from the lower surface. Leaves with blade up to 30mm long, 2mm wide, semi-lanceolate, glabrous with smooth or wavy margins. Flowers up to 20mm diameter, corolla tips yellow to greenish brown, 8mm long, basal portion white, 2mm long. Corolla lobes folded (rolled downwards) longitudinally to form a tube 1mm broad; corolla bulb 4×1mm; corona 2.0mm diameter, flush with the corolla bulb; outer corona appendages forming bifid 0.5mm projections from the 5 nectar pouches, spotted pinkish to purplish, not covering the inner corona lobes, almost transparent; nectar pouches pinkish-spotted; inner corona lobes reduced, greenish on the back of the anthers; pollinia yellow; calyx lobes 2mm long. Seed follicles cylindrical, 50×3 mm, purplish green, slightly decumbent.

Fig. 8  Dug-up plant of C. sideralis to show the almost spherical caudex (Photo: Sally Hey and Susan Armstrong)

Fig. 9  Seed follicle of C. sideralis (Photo: Sally Hey and Susan Armstrong)

Ceropegia sideralis appears to be most closely related to C. occidens (Figs. 2, 4 & 10). Both species have swollen below-ground caudices and fusiform roots. However, the two species differ in several floral and vegetative features (Table 1). The flowers of C. occidens are far smaller than those of C. sideralis and their corolla lobes are shorter and with the tips angled inwards. The main qualitative distinctions from C. occidens are the almost globose caudex (Fig. 8), larger plant size, and morphological differences pertaining to the corolla and corona (Figs. 3–7). Diagnostic features to distinguish between C. sideralis and C. occidens are supplied in Table 1.

Conservation status

Considering the narrow known distribution range of C. sideralis and the fact that the remaining fragments of natural vegetation in areas where the new species grow are under considerable threat from expanding rooibos tea cultivation, it is advisable to carry out surveys in the general area of Graafwater to determine its population size.

 

ACKNOWLEDGEMENTS:

I am grateful to Prof A E van Wyk for initial editing of the manuscript. Special thanks to Dr Mike Picker, who took all the photos of C. sideralis, except for Figs. 8 & 9 taken by Sally Hey and Susan Armstrong.

LITERATURE:

Bruyns, P V, Klak, C & Hanacek, P (2017) A revised, phylogenetically-based concept of Ceropegia (Apocynaceae). South African Journal of Botany 112: 399–436. 

Dyer, R A (1983) Ceropegia, Brachystelma and Riocreuxia in Southern Africa. A.A.Balkema, Rotterdam. 

Email: peckoverralph@gmail.com