Taxonomic name: Carpobrotus edulis (L.) N.E. Br.
Synonyms: Mesembryanthemum edule L., Mesembryanthemum edulis
Common names: balsamo (Catalan-Spain), Cape fig (English-South Africa), figue marine (French), freeway iceplant (English-USA), ghaukum (Afrikaans-South Africa), ghoenavy (Afrikaans-South Africa), highway ice plant (English-USA), higo del Cabo (Spanish), higo marino (Spanish), Hottentosvy (Afrikaans-South Africa), hottentot fig (English-USA), Hottentottenfeige (German), iceplant (English-New Zealand), ikhambi-lamabulawo (Zulu-South Africa), Kaapsevy (Afrikaans-South Africa), patata frita (Catalan-Spain), perdevy (Afrikaans-South Africa), pigface (English-Australia), rankvy (Afrikaans-South Africa), sea fig (English-USA), sour fig (English-South Africa), suurvy (Afrikaans-South Africa), umgongozi (Zulu-South Africa), vyerank (Afrikaans-South Africa)
Organism type: succulent
Carpobrotus edulis is a mat-forming succulent native to South Africa which is invasive primarily in coastal habitats in many parts of the world. It was often introduced as an ornamental plant or used for planting along roadsides, from which it has spread to become invasive. Its main impacts are smothering, reduced regeneration of native flora and changes to soil pH and nutrient regimes.
Carpobrotus edulis is a perennial, mat-forming herb. It is a "robust, flat-growing, trailing perennial, rooting at nodes and forming dense mats. The succulent horizontal stems curve upwards at the growing point. The leaves are succulent, crowded along the stem, 60–130 x 10–12mm, sharply 3-angled and triangular in cross-section with tiny serrations along the outermost angle, yellowish to grass green, and reddish when older. Flowers are solitary, 100–150mm in diameter, yellow, fading to pale pink, produced mainly during late winter–spring (August–October, in native range). This species is easily distinguished from congeners as it is the only one with yellow flowers. In addition, it has more extensive, although very small, serrations along the outer leaf angle. Fruit is fleshy, indehiscent and edible, 35mm in diameter, shaped like a spinning top, on a winged stalk, becoming yellow and fragrant when ripe. The outer wall of the fruit becomes yellowish, wrinkled and leathery with age. The seeds are embedded in the sticky, sweet, jelly-like mucilage. The fruits can be eaten fresh and they have a strong, astringent, salty, sour taste" (Malan and Notten, 2006). If they are not eaten they become very hard and dark reddish brown and decay slowly in place on the stems. IMEP (2001) describe the defining characteristics of C. edulis as: "long tapering leaves with equilateral or obtuse isosceles cross-sections, leaf margins and keel are more or less parallel up to the terminal point area, the centre of mats often die back, and sepals are pointy". C. edulis has a very dense fibrous root system concentrated in the upper 50cm of the soil, with new roots forming at each node as the plant spreads outward (D’Antonio and Mahall, 1991).
Carpobrotus acinaciformis, Carpobrotus affine acinaciformis, Carpobrotus chilensis
In South Africa, Carpobrotus edulis is often seen as a pioneer in disturbed sites. It needs well-drained soil, a sunny position and room to spread. It is an excellent evergreen drought-, and wind-resistant groundcover that can be planted on flat, sandy ground, on loose sand dunes, gravely gardens, lime-rich and brackish soils as well as in containers, rockeries, embankments and will cascade over terrace walls. C. edulis is not frost-hardy (Malan and Notten, 2006). In California, C. edulis depends upon disturbance to open up vegetative cover, but once it becomes established it is competitively superior to native grasses and will overtop them (D’Antonio, 1993). It can invade coastal dune, bluff, scrub, chaparral and coastal grassland habitat. In Australia it has been observed in coastal heathlands. Schmalzer and Hinkle (1987) observe that soil nitrogen levels limit C. edulis growth along highways in California.
Carpobrotus edulis can form impenetrable mats up to 20cm wide and over 50cm deep, and will sometimes compete aggressively with native species (D’Antonio and Mahall 1991, D'Antonio, 1993; PIER, 2005). Once it becomes established, it shows a high vegetative reproductive rate, and its growth does not appear to be affected by herbivory or competition (D’Antonio 1993; Campelo et al. 1999). C. edulis can also decrease species diversity by preventing sand movement, which hinders the natural processes of disturbance and change in dune environments (Kim, undated). C. edulis reduces soil pH and influences nutrient dynamics (D’Antonio 1990a, D'Antonio and Mahall, 1991). C. edulis has been observed to invade new areas following fire events in California (Zedler and Scheid 1988; D'Antonio et al. 1993). C. edulis hybridises with its related species (native, naturalised and alien) in many parts of its introduced range (Chinnock, 1972; Vila and D'Antonio, 1998; Albert et al. 1997; Suehs et al. 2004a; Gallagher et al. 1997), which may intensify the invasion process (Suehs et al. 2004a) or impact on the integrity of native species.
Carpobrotus edulis is used for erosion control, as an ornamental or ground cover, for fruit and as a medicinal plant in folklore (GRIN, 2006).
In its native range, the flowers of C. edulis are pollinated by solitary bees, honey bees, carpenter bees and many beetle species. Fruits are eaten by baboons, rodents, porcupines, antelopes and people, who also disperse the seeds (Malan and Notten, 2006).
Native range: Carpobrotus edulis is native to South Africa, growing on coastal and inland slopes from Namaqualand in the Northern Cape through the Western Cape to the Eastern Cape (Malan and Notten, 2006).
Known introduced range: Portugal, Italy, France, United Kingdom, Ireland, Germany, Spain, Canary Islands, Balearic Islands, Gibraltar, Malta, Albania, Greece, New Zealand, western USA, Australia, St Helena, French Polynesia, Pitcairn, Mexico, Chile, Argentina, Tunisia.
Introduction pathways to new locations
For ornamental purposes:
Other: Carpobrotus edulis has been widely used for erosion control and has been planted along roadsides in California (GRIN, 2006).
Local dispersal methods
Consumption/excretion: Rats and rabbits are the primary seed dispersers of Carpobrotus sp. on offshore islands in southeast France (Bourgeois et al. 2005).
For ornamental purposes (local):
Preventative measures: A Risk Assessment of Carpobrotus edulis for Hawaii and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 9.5 and a recommendation of: "Likely to cause significant ecological or economic harm in Hawaii and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawaii and/or other parts of the world."
Physical: Manual methods appear to be the most effective means of controlling C. edulis at this stage. Albert (1996; in PIER, 2005) recommends: "Hand-pull individual plants and remove any buried stems. Mulch to prevent re-establishment. Large mats can be removed by rolling them up like a carpet". It is important to remove any C. edulis remains during eradication, as any remains left in place become a focus of regeneration, due to the large number of seeds which survive in the fruit for a long time (Fraga et al. 2006).
Another thing to keep in mind following removal of C.edulis is that secondary plant invaders can take advantage of opened areas, spreading rapidly and impeding restoration efforts in coastal dune habitats. C. edulis leaves behind a layer of debris of dead and decaying organic matter that accumulates under the plant. This tends to be left behind after C. edulis is removed. Within the debris are often the dormant seeds of invasive grasses, and these sprout after C. edulis is removed, benefiting from the accumulation of nutrients in the area that C. edulis has facilitated. To avoid this it may be best to selectively remove C. edulis to ensure that some is left behind to stabilise the soil and minimise sand movement into the area. Once the area has been restored to a more natural community, the remaining C. edulis can be removed and that area restored in turn (Kim, undated).
Chemical: PIER (2005) suggest the use of glyphosate herbicides. Schmalzer and Hinkle (1987) reported that there had been no comprehensive survey of herbicide effects on C. edulis. It is assumed that broad spectrum herbicides would kill C. edulis but they may also impact adjacent vegetation. Chlorflurenol, a morphactin, has been used to reduce growth of C. edulis along roadways (Hield and Hemstreet, 1974; in Schmalzer and Hinkle, 1987).
Biological: The options for biological control are currently limited, as the pathogens which attack C. edulis are not specific to it. Verticillium wilt can cause considerable damage (McCain et al. 1974), but using it could cause problems as it also attacks commercial crops (Schmalzer and Hinkle, 1987). Suehs et al. (2004b) state that a constraint on seed production or germination would be the most efficient way to control C. edulis on a long-term basis, if possible, due to its high success in these domains. Two introduced scale insects caused widespread mortality of Carpobrotus edulis plantings in California in the 1970s (Donaldson et al. 1978). As a result the California highway Department introduced natural enemies to control iceplant scale (Tassan et al. 1982). Nonetheless, scale insects have been observed to cause death of clones in California and could be more widely promoted in natural settings.
Carpobrotus edulis is slightly agamospermic, completely self-fertile, slightly preferentially self-compatible, and experiences no inbreeding depression (Vila et al. 1998; Suehs et al. 2004b).
“Active growth of C. edulis occurs primarily along the main axes, although lateral branches may also grow, particularly following death of the apical meristem of the main axis. An individual branch can elongate more than 1m in a year. Branches tend to grow over each other, resulting in the accumulation of up to 40cm of live and dead plant material. Stems exhibit vine like growth and can crawl over shrubs, fences and other obstacles. Rooting occurs at nodes in contact with the soil surface” (D’Antonio, 1990a). The plant is readily cloned by rooting stem fragments that contain at least one node.
Carpobrotus edulis produces a fleshy indehiscent fruit in early spring in California, USA, which remains on the plant until autumn when it is eaten by a variety of native mammals. Uneaten fruits remain on the plants for several years. Ungerminated seeds remain viable in the soil for at least two years (D’Antonio, 1990b). It flowers in April in the Balearic Islands (Universitat de las Illes Balears, undated), and between August and October in South Africa (Malen and Notten, 2006).
Reviewed by: Carla D'Antonio Professor Ecology, Evolution & Marine Biology University of California, Santa Barbara USA
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Sunday, 9 November 2008