Ruschia promontorii
Introduction
The Peninsula cliff ruschia is a mat-forming leaf succulent which becomes pendent on cliffs. It is endemic to the Cape Peninsula, where it grows on sea-facing sandstone cliffs. The green leaves are almost boat-shaped and the flowers are purplish pink, in winter and spring, pollinated by insects. Easily propagated by cuttings and best for fynbos gardens, planted on embankments.
Fig. 1. Ruschia promontorii in habitat flowering in spring at the Cape Point Light House, Cape Point Nature Reserve, among Coleonema album and an orange coloured lichen.
Description
Description
The plants are much-branched, mat-forming, hairless (glabrous) shrublets becoming pendent from cliff faces, with stems up to 500 mm long forming loose hanging mats. The roots are fibrous. The branches are about 3.5 mm in diameter, the main branch up to 5 mm in diameter, reddish at first, biconvex, becoming mottled grey and woody but remaining flaccid, with a smooth surface. The nodes about 15–25 mm apart, 2–3 pairs of leaves grow crowded at the nodes. The leaves are fleshy, sickle-shaped, 3-angled (trigonous) owing to the deep prominent keel (5–7 mm), green to yellowish green, reddish at tips and on keels, 10–20 × 5–7 mm, when viewed dorsally they are triangular-ovate, ascending. The leaves may become reddish during summer due to the betanin pigments. The leaf surface is smooth, the upper surface somewhat flat, the leaf tip acute, and bearing a prominent little point (mucro). The flowers are solitary, up to 30 mm in diameter, the flower stalks (pedicels) about 7 mm long. The flower petals are linear and purplish pink. The anthers yellow. The young fruits at first cup-shaped, later top-shaped, 7–9 mm in diameter, 5–6 mm deep, with closing body. The fruit is at first reddish, becoming light grey. The seed is pear-shaped, 1.5 × 1 mm, minutely tuberculate, light brown. Flowering time is mainly in winter and spring (July to October).
Fig. 2. Ruschia promontorii flowering on the coastal cliffs of Paulsberg, Cape Point Nature Reserve, in October 2010, and a close-up of the leaves and young, reddish stems that become mottled grey and woody but remain flaccid.
Conservation Status
Status
Classified as Rare by the Red List of South African Plants, it is a range-restricted habitat-specialist which is not threatened (Van Jaarsveld et al 2005).
Distribution and habitat
Distribution description
Ruschia promontorii is a quarzitic sandstone endemic of the southern Cape Peninsula mountains in the Western Cape, growing at altitudes of 20 to 400 m above sea level. It is only known from the southern Cape Peninsula. It grows on cliffs between Smitswinkel Bay to Cape Point, part of its range falls in the Cape Point Nature Reserve, where it is mainly confined to east-facing coastal cliffs on Paulsberg and Vasco da Gama Peak. Outside of the Cape Point National Park it grows on western aspects on sea-facing cliffs from Scarborough to Chapman’s Peak. Plants grow rooted in crevices and on ledges, drooping over the rock faces. The temperatures are relatively moderate throughout the year. The average daily maximum temperature is about 20°C and average daily minimum for the region 12°C. Rainfall occurs mainly in winter and is estimated to be about 300–400 mm per annum.
Fig. 3. The cliffs of Paulsberg, Cape Point Nature Reserve, and a close-up of Ruschia promontorii growing on the cliff among Aloe succotrina and Tylecodon paniculatus in October 2010.
Plants grow in Peninsula Sandstone Fynbos (Mucina et al. 2005). Near the light house at Cape Point, Ruschia promontorii shares its habitat with Coleonema album, Cotyledon orbiculata var. orbiculata, Crassula nudicaulis, Cussonia thyrsiflora, Drosanthemum candens, Tylecodon grandiflorus and T. paniculatus. The geology consists of quartzitic sandstone of the Table Mountain Group (Cape Supergroup). At Smitswinkel Bay it grows on cliffs relatively close to the sea and shares its habitat with Curio repens (= Senecio serpens), Crassula scabra and Eriocephalus racemosus. On the Paulsberg it grows with Coleonema album, Tylecodon paniculatus and Aloe succotrina. The fruticose lichens in the habitat are indicative of the moist air. At Chapmans Peak plants were observed growing with Aloe maculata, Adromischus hemisphaericus, Drosanthemeum candens, Othonna arborescens, Othonna dentata and Ruschia macowaniana.
Fig. 4. The cliffs above Smitswinkel Bay, habitat of Ruschia promontorii, where the plants grow close to the sea (March 2010).
Derivation of name and historical aspects
History
Ruschia promontorii was named by Louisa Bolus in 1929 in Notes on Mesembryanthemum and allied genera. She aptly named it promontorii which refers to the Cape Peninsula in the Western Cape, in particular Cape Point, a promontory where the plant occurs. This plant has not been found outside of the Cape Peninsula. The genus name honours Ernst Julius Rusch (1867–1957), a Namibian farmer and collector of succulent plants (Clarke & Charters 2016). Ruschia is the largest genus within the family Aizoaceae, previously called Mesembryanthemaceae, with more than 400 species having being named. It is very variable with distinct groups and many species have been moved to other genera, and today 208 species of Ruschia are recognized.
Fig. 5. The coastal cliffs at the Cape Point Light House, Cape Point Nature Reserve, in spring (September 2011), habitat of Ruschia promontorii.
Ruschia promontorii was erroneously placed in synonymy under Amphibolia laevis by Hartmann in 2001, based on leaf similarity and lack of fruits on the type specimen of R. promontorii, but was re-instated by Klak in 2020 after studying the fruits and establishing that they are not typical of Amphibolia.
Closely related to Ruschia rubricaulis, an ascending to sprawling shrublet with angular branches, trigonous leaves and solitary rose-pink flowers to 15 mm in diameter, occurring in the northern Peninsula at Leeukop. The latter is easily differentiated by its longer leaves (20–40 mm long) with finely serrulate keels and margins and glaucous green colour. (Klak et al 2020) The population of R. promontorii at Chapmans Peak has slightly longer leaves than the more southerly populations.
The Cape Peninsula is rich in mesembs and 56 species represented in 19 genera have been recorded. The largest genus is Lampranthus with 19 species. Ruschia promontorii is one of 7 species and also the only obligatory cliff dwelling mesemb on the Cape Peninsula (Bolus 1928, Adamson & Salter 1950).
Fig. 6. Ruschia promontorii in habitat in spring drooping over a sandstone cliff in the Cape Point Nature Reserve. Note the young, reddish, cup-shaped fruits.
Ecology
Ecology
The plants grow firmly rooted in shallow pockets of soil in crevices and on narrow rocky ledges on sea-facing cliffs which are exposed to salt-laden sea breezes. The succulent leaves enable the plant to withstand periods of drought. The presence of numerous species of lichens reflects the moist air and regular fog. The leaves turn reddish to yellowish during the summer due to the betanin pigment which slows down the process of photosynthesis. The sprawling to pendent, leafy stems are retained in cultivation. A fairly long-lived perennial. On cliffs the stems become pendent, forming loose mats. Stems and leaves are soft and flaccid, a character that can be viewed as a reduction in armament as a result of the undisturbed cliff habitat. The flowers are produced on new growth towards the branch tips. The purplish-pink colour is conspicuous, maximising visibility for successful pollination by insects in the vertical cliff environment. Flowering time is in winter and spring, ensuring a long and continual seed supply. The fruiting capsules open with rain and the seeds dispersed by rainwater, settling and germinating in crevices. The seeds, compared to many other mesembs, are large, 1.5 mm in diameter, and minutely tuberculate, ideal size for establishment in rock crevices. It germinates in autumn and winter, coinciding with the rainfall. Germination can be within 3 weeks.
Plants increase vegetatively, forming small mats that become pendent, the branches (vegetative growth) rooting where they touch the soil, an efficient vegetative dispersal backup and adaptation to the cliff face, ensuring long-term survival.
Fig. 7. Ruschia promontorii trailing over a cliff at Paulsberg, Cape Point Nature Reserve. Note the numerous orange coloured fruticose lichens.
Uses
Use
Ruschia promontorii can be grown as a garden ornamental, no other uses have been recorded.
Fig. 8. Ruschia promontorii flowering in spring, growing on a ledge on the cliffs at the Cape Point Light House, Cape Point Nature Reserve.
Growing Ruschia promontorii
Grow
Best for cool fynbos and other warm temperate Mediterranean climate gardens, grown in containers or rockeries (Van Jaarsveld 2010). Although the plant is easily propagated, when planted, it should be grown in areas away from aggressively growing species which would outcompete the plant. Outside its habitat, it is best grown under controlled conditions in a greenhouse. The plant grows naturally on mineral-poor acidic sandstone soil. Does well in containers in full sun or dappled shade. Can be re-potted every second year. When the plant becomes untidy, refresh from cuttings. Grow as a ground cover on steep embankments or rockeries, preferably in full sun. Establishing time is autumn with the onset of autumn rain. They grow moderately and should flower during the first season.
Propagate from cuttings or seed. Take stem cuttings in winter, spring or summer, and plant in a sandy soil mixture. Cuttings should be about 8–12 cm in length, remove the lower leaves and plant the stems to a depth of about 1–2 cm. Keep moist until well rooted. Rooting will take place within 3 weeks.
Sow seed in autumn or winter, in shallow trays in a sandy soil. Cover the seed with a thin layer of sand (1–2 mm) and keep moist. The Kirstenbosch seed primer (a smoke treatment) should enhance the germination process.
Plants grow well in a general succulent mixture, such as 2 parts sand, 1 part garden loam and 1 part peat or well broken down compost, and good drainage is essential.
References
- Adamson, R.S. & Salter, T.H (eds). 1950. Flora of the Cape Peninsula. Juta, Cape Town.
- Bolus, H.M.L. 1928. Mesembryanthemum and some allied genera Part 1. University of Cape Town, Bolus Herbarium.
- Bolus, H.M.L. 1929. Notes on Mesembryanthemum and allied genera. Part 2. University of Cape Town.
- Clarke, H. & Charters, M. 2016. The illustrated dictionary of southern African plant names. Flora & Fauna Publications Trust, Jacana, Johannesburg.
- Hartmann, H.E.K. 1991. Mesembryanthema. Systematics, biology and evolution of some South African taxa. Contributions from the Bolus Herbarium. No. 13: 75–157.
- Hartmann, H.E.K. 2001. Aizoaceae F-Z. In Eggli, U. & Hartmann, H.E.K. (eds.). Handbook of Succulent Plants. Springer. Heidelberg, New York, etc.
- Klak, C., Schmiedel, U. & Bruyns, P.V. 2020. The taxonomic status of Ruschia stricta var. turgida and R. promontori and a new name for R. vaginata (Ruschieae, Aizoaceae). Phytotaxa 433(1):41-54.
- Manning, J. & Goldblatt, P. 2012. Plants of the Greater Cape Floristic Region 1: the Core Cape Flora. Strelitzia 29. South African National Biodiversity Institute, Pretoria.
- Mucina, L. & Rutherford, M.C. (eds) 2006. The vegetation of South Africa, Lesotho and Swaziland. Strelitzia 19. South African National Biodiversity Institute, Pretoria.
- Plants of the World Online, Ruschia Schwantes. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:16337-1. Accessed 27/02/2024.
- Van Jaarsveld, E.J. & Pienaar, U. de V. 2000. Vygies, gems of the veld. Cactus & Co. Libri, Venegono, Italy.
- Van Jaarsveld, E.J. 2010. Waterwise gardening in South Africa and Namibia. Struik, Cape Town.
- Van Jaarsveld, E.J., Helme, N.A. & Potter, L. 2005. Ruschia promontorii L.Bolus. National Assessment: Red List of South African Plants version 2020.1. Accessed on 2024/02/26.
Credits
Ernst van Jaarsveld
Kirstenbosch National Botanical Garden (Retired)
Babylonstoren Farm (Current)
Extraordinary senior lecturer and researcher,
Department of Biodiversity and Conservation, University of the Western Cape
March 2024
Plant Attributes:
Plant Type: Ground Cover, Succulent
SA Distribution: Western Cape
Soil type: Sandy
Flowering season: Spring, Winter
PH: Acid
Flower colour: Pink
Aspect: Full Sun, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Average
Special Features:
Drought resistant
Good potplant
Feeds honeybees
Horticultural zones
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