Curio is a genus of succulent flowering plants in the daisy family Asteraceae (tribe Senecioneae), comprising about 20 accepted species. The genus was established by English botanist Paul V. Heath, described and published in the journal Calyx in 1997, when a group of succulent species were segregated from the much larger and morphologically diverse genus Senecio. All species in Curio were formerly classified under Senecio, and many retain their former Senecio names in common use.
Plants in the genus are evergreen succulents typically grown for their unusual and ornamental foliage. They are characterised by striated (grooved) succulent leaves that take a variety of distinctive shapes across species — spherical bead-like leaves in C. rowleyanus, elongated banana-shaped leaves in C. radicans, teardrops in C. hallianus, and flattened blue-glaucous leaves in C. ficoides. Flower heads are discoid, lacking the showy ray florets typical of many composites; instead they bear small clusters of tubular florets that are often white or cream and lightly fragrant.
The genus is native primarily to southern Africa, particularly South Africa and Namibia, where species grow in rocky, arid, and semi-arid habitats. Several species are adapted to trailing or clambering growth, making them well suited to hanging baskets and cascading displays in cultivation. Curio are among the most widely grown succulent genera in horticulture worldwide, with C. rowleyanus (String of Pearls) and C. radicans (String of Bananas) particularly popular as houseplants.
Distribution
Curio species are native to southern Africa. The genus as a whole has its centre of diversity in South Africa and Namibia, where individual species occupy rocky outcrops, cliff faces, and arid scrubland. Species such as Curio repens and Curio ficoides are found along the Cape coast and Karoo regions of South Africa, while others such as Curio avasimontanus occur in Namibia. Curio pondoensis is restricted to the Pondoland region of the Eastern Cape, reflecting a pattern of localised endemism within the genus. Outside their native range, several species — particularly C. rowleyanus and C. radicans — have become naturalised in parts of the Mediterranean basin, California, and other mild-climate regions where they have escaped cultivation.
Ecology
As succulents adapted to semi-arid environments, Curio species are drought-tolerant and typically grow in well-drained, rocky or sandy substrates with low soil fertility. Their succulent leaves store water, enabling survival through seasonal dry periods. Striated leaf surfaces reduce solar heat load. In their native habitat, species often grow in partial shade beneath shrubs or on sheltered cliff faces, receiving bright but indirect light for much of the day. The discoid flower heads, while small, attract pollinators including small bees and flies. Trailing or sprawling growth habits in species like C. rowleyanus and C. radicans allow the plants to root at nodes along pendant stems, an adaptation to colonising rocky ledges and cliff overhangs.
Cultivation
Curio are popular ornamental succulents grown primarily as houseplants and container plants in temperate climates, and outdoors year-round in frost-free regions. They require bright, indirect light indoors or full sun with some afternoon shade outdoors; direct harsh midday sun can scorch leaves. Well-draining gritty or sandy soil is essential — standard cactus and succulent mixes are suitable. Watering should be infrequent: allow the soil to dry out almost completely between waterings, then water thoroughly. Overwatering is the most common cause of failure and leads to root rot. Plants are not frost-hardy and should be kept above 5°C (41°F). Trailing species are best displayed in hanging baskets where stems can cascade freely. Curio rowleyanus and C. radicans are among the most frequently cultivated members of the genus.
Propagation
Curio species propagate readily from stem cuttings. Trailing species such as C. rowleyanus and C. radicans can be rooted by laying cut stems on the surface of moist, gritty compost and allowing the nodes to make contact with the substrate; roots emerge from the nodes within a few weeks. Cuttings should be allowed to callus for a day or two before placing on compost to reduce the risk of rotting. Division of congested clumps is also possible for clustering or clumping species. Seed propagation is less common in cultivation but is practised for some species.
Taxonomy
Curio P.V.Heath was formally described by English botanist Paul V. Heath and published in Calyx 5(4): 136 in 1997 as a nomen novum — a replacement name for a circumscribed group of succulent species previously placed in Senecio. The genus belongs to the family Asteraceae, order Asterales, and is placed within the tribe Senecioneae and subfamily Asteroideae. Under the GBIF backbone, the genus holds 32 descendant taxa (accepted species plus synonyms), with 21 species currently treated as accepted. All accepted species bear basionyms with authors including Linnaeus, de Candolle, Schlechtendal, and others, reflecting the long history of these plants in the botanical literature under Senecio before the 1997 reclassification. The hybrid Curio ×peregrinus (String of Dolphins), a cross between C. rowleyanus and C. articulatus, is also formally accepted at species rank.
