Ceropegia linearis subsp. woodii
Ceropegia linearis E.Mey. subsp. woodii (Schltr.) H.Huber.
Common names: string of hearts, necklace vine, rosary vine, Wood’s ceropegia, hanging milkwort, Jacob’s beard, little pitchers, chain of hearts, collar of hearts, hearts entangled, hearts-on-a-string, sweetheart vine, heart vine (Eng.); halssnoer-ranker (Afr.); isidakwa, uvemvane samatshe, uvemvane lwamatshe (Zul.)
This dainty little Ceropegia, sometimes also known as Ceropegia woodii, is globally probably one of the most widely cultivated of all the species of this genus. With its small pinkish flowers and aerial tubers formed at the nodes along the stems, it is an easy to grow and excellently rewarding ornamental houseplant. It makes for an effective subject as trailer for hanging pots or baskets and is an excellent indoor plant that grow well in half shade with average water, is evergreen, but tender to frost.
Figure 1. Close-up of Ceropegia linearis subsp. woodii flower and leaf. (Photo M. Koekemoer)
Ceropegia linearis subsp. woodii is a perennial, evergreen, succulent climber or prostrate trailer, with slender, prostrate stems arising from tubers. Tuber with a hard, grey and woody base, usually wrinkled that grows up to 25–50 mm in diameter.
Figure 2. Stems with warty potato-like aerial tubers developing at the nodes. (Photos S.P. Bester)
From the tuber grows thin, pinkish stems 0.25–1.0(–3) m long. Leaves opposite, fleshy, ovate-lanceolate or heart-shaped (orbicular with a cordate base), 6–18 mm in diameter, sometimes whitish to silver along the veins, with short petioles and internodes ± 30–80 mm long. The leaves are dark green marbled with silvery white on the upper surface and purple on the underside.
Figure 3. Leaves of Ceropegia linearis subsp. woodii. A, ovate blade with cordate base; B, heart-shaped leaves; C, leaves are succulent and opposite at the nodes; D, leaves getting dappled light develop marbled surfaces. (Photos S.P. Bester)
The inflorescences (cymes) are 1–4-flowered and are produced in succession; the pedicels 3–10 mm long. At various lengths along the stem, aerial tuberous growths are produced. Flowers have an 18–25 mm long tube (straight or sometimes slightly curved) with dark, longitudinal stripes, with an inflated globose base ± 4 mm in diameter. The lobes are spoon-shaped, 6–8 × 3.0–4.5 mm, fused at the tips to form cage-like structures, forming a white canopy; the margins contain purplish hairs inside.
Figure 4. Pendulant stems with leaves and flowers, in habitat. (Photo Mervyn Lötter)
In the swollen base of the tube, the gynostegium (fused anthers and pistils) with corona lobes, are found where the pollinia is situated that is transferred via the pollinator to another flower, to facilitate pollination. Fruit narrow spindle-shaped follicles, 50–70 × 3 mm.
Figure 5. Floral parts of Ceropegia linearis subsp. woodii. A, apical portion showing the lobes with hairs on their margins and the tips fused to form a cage-like structure with open sinuses (or windows) that are entry points to the tube. B, a full flower showing the basal inflation that houses the gynostegium, the tube and the lobes. C, dissected part of the tube showing the maroon longitudinal striping and downwards-directed hairs that guide a pollinator to the basal inflation. Photos S.P. Bester)
In cultivation, flowers may appear sporadically throughout the year, but wild plants have not been recorded in flower for June and September. They usually flower in summer to autumn (mainly December–April).
Figure 6. The basal inflation of the corolla in Ceropegia linearis subsp. woodii. A, showing the position of the gynostegium and again the downward-directed hairs. B, close-up of the gynostegium showing the inner and outer corona lobes that secrete nectar to keep possible pollinators alive while temporarily caught in the ‘trap’-flower. C, close-up of gynostegium showing the pollinaria that are attached by a clip which usually catch the proboscis or feet or antenna of a pollinator by which means it is removed from this particular flower and deposited on another flower in subsequent visits. (Photographs S.P. Bester)
The current conservation status is Least Concern (LC) (Foden & Potter 2005). This taxon was not selected in any one of four screening processes for highlighting potential taxa of conservation concern for detailed assessment and was hence given an automated status of Least Concern. The Threatened Species Programme is currently systematically completing full assessments for all taxa with an automated status.
Figure 7. Known distribution of Ceropegia linearis subsp woodii based on distribution records at the National Herbarium (PRE).
Distribution and habitat
Found in the Limpopo, Mpumalanga, KwaZulu-Natal, Western and Eastern Cape Provinces of South Africa. This species is also native to Mozambique, Eswatini and Zimbabwe.
Figure 8. Various plants of Ceropegia linearis subsp. woodii in habitat in rocky patches with shallow soils in ledges within indigenous forests. (Photos Judd Kirkel)
Plants are found growing naturally mostly on rocky ledges within forests from 100–1 180 m above sea level. The tubers are usually embedded in cracks with a thin layer of soil on these cliff edges. It may also be found in open or closed woodland, outcrops and ledges in forests and rarely in grassland. The soils are usually rich in humus, loam or sandy soils that may be rocky or gravelly. Plants are usually found in shaded places. The natural habitat is in frost-free areas with relative high rainfall (600–1 000 mm per annum), with average maximum temperature of about 26ºC and average minimum temperature of 16ºC. Typically, many species of Ceropegia grow and climb naturally among bushes which provide shade and humidity to the base, whereas the vegetative growth is in the light.
Figure 9. Ceropegia linearis subsp. woodii in habitat. A, aerial tubers pressed against the soil surface eventually root (note the connection of the stem between these tubers here depicted). (Photo A Graham Grieve) B, Flowering stems with leaves amongst humic-rich soils and leaf litter on the forest floor. (Photo B Judd Kirkel)
Subspecies linearis has a restricted distribution on the coastal areas of southern KwaZulu-Natal from about Port Shepstone to just across the border to the Eastern Cape, in a narrow zone along the coast of the former Transkei. Subspecies woodii has a much wider distribution from the mountainous regions of the northern parts of Limpopo Province, through Mpumalanga, the KwaZulu-Natal midlands, southwards and sporadically in the Eastern Cape.
Derivation of name and historical aspects
Linnaeus named the genus to describe the appearance of the flowers as fountains of wax, from the Greek words keros, meaning ‘wax’ and pege, meaning ‘fountain’. The subspecific epithet is in honour of John Medley Wood (1827–1915), a former curator of the Natal Herbarium. Ceropegia linearis subsp. woodii (=Ceropegia woodii) was first described by Rudolph Schlechter from material collected by Medley Wood and Evans in KwaZulu-Natal, in 1881.
The closely related and similar subspecies Ceropegia linearis subsp. linearis is different to the subspecies woodii by having linear leaves and long, narrow and straight segments that form the cage, and are merely connate and do not form a canopy. The subspecies woodii has at various times been regarded as a species in its own right (Ceropegia woodii) or as a subspecies within C. linearis.
Figure 10. Ceropegia linearis subsp. linearis. A, stems with inflorescences – flowers open successively in each inflorescence. B, subspecies linearis is distinguished morphologically on the distinctly longer (linear) segments and straight tube (the coronas are also markedly different with subsp. woodii having much longer inner lobes and in subspecies linearis they are broad and somewhat falcate). C, the leaves of subspecies linearis are also markedly different, without obvious mottling, venation, shame and are homogenously coloured. (Photos S.P. Bester)
The genus Ceropegia in the strict sense consist of about 170–220 species (depending on the authority followed), distributed throughout Africa, Madagascar, Asia and northern Australia, with ± 65 species in southern Africa where they are widespread, but particularly rare in the Western Cape Province. Ceropegia ampliata and C. crassifolia subsp. crassifolia have previously been covered in this series. Many of these perennial plants have succulent stems, which may be dwarf or vine-like and have fibrous roots, whereas others have tubers and relatively thin stems, along which new tubers may form in some species. Species with fleshy thickened roots, are the most difficult to grow.
The pollination of the tubular flowers has most probably developed because of pollination pressure by the wide range of insects within the Diptera (flies). Almost all Ceropegia in the strict sense have specialized trap-flowers with internal structures to temporarily imprison the possible pollinator for some time.
After successful pollination, seeds develop in horn-shaped fruits that are characteristic of the milkweed family, called follicles. A follicle is a pod that arises from a single carpel that splits on the inside along a single suture. The follicles are usually paired, but may be solitary due to abortion of one of the carpels. Each bursts open by a single longitudinal slit and contain stacks of flat seeds. Each seed has a coma of hairs on one side and as soon as the follicle bursts open, these hairs start to spread because of the change in moisture in the air, in their immediate vicinity. This causes the fibers of the coma to spread out and form a parachute-like structure attached to an individual seed. The coma is sensitive to the slightest air movement and the lightest breeze will carry the seed off for dispersal.
The possible pollinators (mostly small flies), are attracted by the scent given off by the flowers and the potential pollinator will enter the flowers through the openings at the top of the flower (‘windows’). On the inside of the tube there are long hairs, usually facing downwards into the tube. This is responsible for a one-way direction movement of the pollinator down to the inflation at the bottom of the tube. The insect is thus prevented from escaping until the hairs wither, and the fly can then escape,hopefully with pollinia (a mass of pollen grains that are transferred as a group) attached to its body, to be transferred to the next flower the fly visits.
Plants are mainly used in the horticultural industry as effective trailing plants, usually grown in hanging pots or baskets. The stems can alternatively be trained upwards on miniature trellises. Most indoor gardeners let the stems hang over the side of the container to display the decorative mottled leaves and aerial tubers produced along the stems.
In the wild it is well-known that especially the tubers of Brachystelma and Ceropegia plants are not only consumed as survival food and for their water content by man, but also by wild animals like porcupine, baboons, and rodents and even insects. Stems and tubers may be eaten raw as a famine food, or to utilize the moisture derived from them.
Plants are used in traditional Zulu medicine by pounding the stems and leaves and making an infusion of these for the treatment, as an emetic, for chest complaints thought to be caused by poisoning.
The tubers of both subspecies of Ceropegia linearis are used in grafting stapeliads which are difficult to root.
Growing Ceropegia linearis subsp. woodii
Plants are easily grown from seed, stem cuttings or aerial tubers produced along the stems. Use equal parts of a soil-based potting mixture, coarse sand and perlite as growing medium. Make sure drainage is good. All propagation should be done in the time of active growth (summer).
Plants may be propagated easily from seed, if obtainable. Sow seed in spring in a seedling soil mix and cover with a few millimeters of fine sand. Keep moist, and seeds will germinate in about 1–2 weeks.
Aerial tubers can be used as anchor. Best is to use a tuber of ± 2 cm in diameter. Place the tuber on top of ± 2.5 cm coarse sand and perlite mixture to prevent rotting and cover with thin layer of fine sand. Place newly potted tubers or stem in medium light and water sparingly until feeder roots are established (to ± 8 weeks – in this time no aerial growth will be seen until the roots are well established).
Stem cuttings can be made by pruning some of the vine, to get stems with at least a couple of internodes. Place them in a container with water. Place the cuttings in a position of good light and moderate temperature and wait for roots to form from the stems or nodes. Roots should appear after a few days to weeks, depending on the light and temperature; after the cuttings have rooted, they can be potted.
Plants need ample light, at least 3–4 hours of direct sunlight a day, especially when indoors, less causes the stems to elongate and the leaves to lose their colouration so that they become homogenously green. Normal room temperature is suitable throughout the year. Water sparingly in the active growing period and only keep potting mixture moist, not wet or soggy; allow the top two thirds to dry out between watering. Reduce watering further in the dormant phase (winter), but still do not let the potting mixture dry out fully. A plant can grow for a couple of years in a pot or when more than one tuber is planted in a pot, space them 3.5–5.0 cm apart. It is the ideal hanging plant, with its heart-shaped leaves growing on thin vines.
Feed mature plants with liquid fertilizer once a month during the active growing season, but the concentration should be half of what is prescribed, in order not to burn the roots or tuber.
Rosary vines prefer warm temperature and bright light, but should not be placed in direct sunlight. When grown indoors, the optimum temperature is 25–30ºC in summer and preferably not below 15ºC in winter. String of hearts is an easy plant to grow and durable and an excellent house plant. It is regarded as a leaf-succulent vine.
This plant can be grown outdoors in tropical or subtropical climates, but is also an easy indoor plant that can be grown on a sunny window sill. In strong light the leaves will be darkly coloured, with distinctive marbling; if not given enough light they will be a light green colour. Houseplants could be moved outside in summer, but need to be acclimatized gradually to the stronger light, to prevent sunburn. If moved outside, be sure to bring indoors before the first frost. In winter, keep the plants in relatively warm conditions, above 15ºC. A minimum over-wintering temperature of 10ºC is adequate, providing the plants are kept relatively dry then.
Too much water can cause the thickened white roots of many Ceropegia species or the tubers such as those of Ceropegia linearis subsp. woodii not only to rot, but make them susceptible to woolly aphid infestation.
- Bester, S.P. 2004-05. Ceropegia ampliata (Apocynaceae). PlantZAfrica. http://pza.sanbi.org/ceropegia-ampliata
- Bester, S.P. 2019-02. Ceropegia crassifolia var. crassifolia (Apocynaceae). PlantZAfrica. Online. http://pza.sanbi.org/ceropegia-crassifolia-var-crassifolia
- Dyer, R.A. 1980. Brachystelma, Ceropegia and Riocreuxia. In: O.A. Leistner (ed). Flora of southern Africa 27 Part 4: 1–88. Botanical Research Institute, Pretoria.
- Dyer, R.A. 1983. Ceropegia, Brachystelma and Riocruexia in southern Africa. Balkema, Rotterdam
- Foden, W. & Potter, L. 2005. Ceropegia linearis E.Mey. subsp. woodii (Schltr.) H.Huber. National Assessment: Red List of South African plants version 2017.1. Accessed on 2019/11/05
- Frandsen, R. 2017. Succulents of southern Africa. Honeyguide Publications, Somerset West.
- Germishuizen, G. & Fabian, A. 1997. Wild flowers of northern South Africa. Fernwood Press, Vlaeberg, Cape Town.
- Houseplant Central. String of Hearts, how to propagate Ceropegia woodii. https://houseplantcentral.com/chain-of-hearts-how-to-propagate/ Accessed on 5 Nov. 2019.
- Hulme, M.M. 1954. Wild flowers of Natal. Shuter & Shooter, Pietermaritzburg.
- Hutchings, A., Scott, A.H., Lewis, G. & Cunningham, A.B. 1996. Zulu medicinal plants: an inventory. University of Natal Press, Pietermaritzburg.
- Huxley, A. (ed.). 1981. Success with house plants. Reader’s Digest. Pleasantville, New York.
- Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Mayr, S. 2010. String of hearts, Ceropegia woodii. Master Gardener Program, Division of Extension, University of Wisconsin-Madison. Online. https://wimastergardener.org/article/string-of-hearts-ceropegia-woodii/
- Meve, U. 2002. Ceropegia in F.Albers & U.Meve (eds), Illustrated handbook of succulent plants. Springer, Berlin.
- Pienaar, K. 1984. The South African what flower is that? Struik, Cape Town.
- Pole-Evans, I.B. 1930. Ceropegia barbertonensis. The Flowering Plants of South Africa. Vol. 10: t. 387.
- Pole-Evans, I.B. 1930. Ceropegia woodii The Flowering Plants of South Africa. Vol. 10: t. 382.
- Pooley, E. 2005. A field guide to wild flowers KwaZulu-Natal and the eastern regions. The Flora Publications Trust, Durban.
- Smith, G.F., Crouch, N.R. & Figueiredo, E. 2017. Field guide to succulents in southern Africa. Struik Nature, Cape Town.
- World of Succulents, Succulentopedia. Ceropegia linearis subsp. woodii (String of Hearts). https://worldofsucculents.com/ceropegia-linearis-subsp-woodii-string-of-hearts-rosary-vine/. Accessed on 5 Nov. 2019.
- World of Succulents, Succulentopedia. Ceropegia linearis. https://worldofsucculents.com/ceropegia-linearis/. Accessed on 5 Nov. 2019
- World of Succulents, Succulentopedia. How to grow and care for Ceropegia. https://worldofsucculents.com/how-to-grow-and-care-for-ceropegia/. Accessed on 5 Nov. 2019
Stoffel Petrus Bester
Biosystematics and Collections Division, National Herbarium, Pretoria
Acknowledgements: the author sincerely thanks the following people for kindly making their images available for use in this contribution: Graham Grieve, Judd Kirkel-Welwitch, Marinda Koekemoer, Mervyn Lötter and Cameron McMaster.
Plant Type: Climber, Succulent
SA Distribution: Eastern Cape, KwaZulu-Natal, Limpopo, Mpumalanga
Soil type: Sandy, Loam
Flowering season: Early Summer, Late Summer, Autumn, Sporadic/All year
Flower colour: Purple, Pink, Cream
Aspect: Shade, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Easy