Ecology Distribution Management Info Impact Info References and Links Contacts

Taxonomic name: Celastrus orbiculatus Thunb. Synonyms: Celastrus articulatus Thunb., Celastrus orbiculata Thunb. Common names: Asian bittersweet, Asiatic bittersweet (English), climbing spindleberry (English), Japanese bittersweet, oriental bittersweet (English), Rundblättriger Baumwürger (German), tsuru-ume-mo-doki (Japanese) Organism type: vine, climber Celastrus orbiculatus is a deciduous, dioecious round-leaved vine that makes use of the 'sit and wait' invasion strategy. This species establishes under closed canopy forest conditions and persists indefinitely until it is released by a disturbance that creates conditions optimal for rapid growth. It invades forested land but has also been known to persist on coasts and may possibly disrupt dune formations. C. orbiculatus can overtop and girdle native trees and shrubs along roads, in clearings and in forest gaps. Identifying and eradicating populations before it they are released by an opening in the canopy is the easiest method of control. Description C. orbiculatus is described as a deciduous, woody, perennial vine from the staff-tree family (Celastraceae), which sometimes occurs as a trailing shrub. Also known as round-leaved and oriental bittersweet, stems of older plants sometimes grow to 10cm (4 inches) in diameter. Leaves of oriental bittersweet are glossy, rounded, finely toothed and arranged alternately along the stem. Clusters of small greenish flowers emerge from leaf axils, allowing each plant to produce large numbers of seeds. Dreyer (2003) recognises the following identification characterisitics of C. orbiculatus: Axillary buds are 1-3mm long, rounded, with outer scales sometimes becoming spine-like. Leaves are glabrous, alternate in arrangement and extremely variable in size and shape, from broadly oblong-obovate to suborbicular, 2 -12cm long and 1.5 to 8cm wide. Leaf margins are crenate-serrate and leaf base cuneate to obtuse, tip acute to rounded. Petioles are 1-3cm long. Inflorescences are axillary cymes, usually containing 3 - 7 flowers. However inflorescences are sometimes terminal in male plants. Flowers are small, greenish-yellow, and usually become unisexual by abortion or reduction of male or female parts, thus the plants are usually dioecious. Occasional vines develop both unisexual and perfect flowers and are then termed polygamo-dioecious. Another reported variation is occasional monoecious plants, i.e. with both male and female flowers on the same vine. The flowers have 5 sepals and 5 petals. Male flowers contain 5 stamens which are about as long as the petals and inserted at the edge of a cup-shaped disk around a vestigial pistil. Female flowers have vestigial stamens, a 3-lobed stigma, columnar style and well a developed superior ovary, sometimes embedded in the disk. The fruit are globose, loculicidal capsules, 6 to 8mm in diameter, which change in colour from green to bright yellow as they mature. The capsules are three valved with each valve (locule) containing one or two brown seeds completely enclosed in a fleshy red aril. Upon ripening, the yellow outer covering splits open to reveal the red aril, thus presenting a brightly bicoloured "dispersal flag". Similar Species Celastrus scandens More Occurs in: agricultural areas, coastland, natural forests, planted forests, range/grasslands, riparian zones, ruderal/disturbed, scrub/shrublands, urban areas Habitat description Oriental bittersweet dominates gap and edge environments, but may also colonise undisturbed forest (Ellsworth et al. 2004b). Dreyer (2003) states, "Its North American habitat preferences have been stated as wide. It is variously described as occupying open woods and thickets, roadsides, fence-rows, and thickets, alluvial woods, roadsides and thickets". General impacts McNab and Loftis (2002) observe that, C. orbiculatus characteristics of shade tolerance, rapid growth response upon release from shading, prolific and consistent annual seed production with high viability and germination, and, adaptation to a wide range of suitable environments make it highly competitive with native vegetation and potentially difficult to manage in forests that are subject to recurrent natural or managed disturbance. Ellsworth et al. (2004) state, "Once established, C. orbiculatus can overtop and girdle native trees and shrubs along roads, in clearings and in forest gaps". The success of C. orbiculatus may be due to frequent natural and human-caused disturbances in the eastern U.S. (Robertson et al. 1994 ; Luken et al. 1997 ; McDonnell et al. 1997 ; McNab and Loftis, 2002 ). Disturbances can lead to plant invasions through an increase in the availability of resources such as germination sites, light and water (Hobbs and Huenneke, 1992 ; Greenberg et al. 2001 ). However, it has also been suggested that C. orbiculatus seedlings can become established and survive in intact forest understory (Paterson, 1974 , 1975 ; Greenberg et al. 2001 ). This ability has important implications for forest management because disturbances that result in increases in light may release C. orbiculatus already established in the understory. Silveri et al. (2001) state that, "The annual growth rate of C. orbiculatus may exceed 3m (Paterson 1974), allowing plants in open-light habitats to climb a canopy-sized tree in 3-4 growing seasons. Twining vines are generally limited to small-diameter supports (Teramura et al. 1991), but C. orbiculatus is able to climb tree trunks with a wide variety of diameters, aided by spiny projections around its bud and leaf scars that lodge in the host's bark. C. orbiculatus kills other vegetation through blanketing and constrictive twining, and halts the succession of young deciduous forests (McNab and Meeker 1987; Dreyer 1994)." Ellsworth et al. (2004) also suggest that failure to control it would result in severe forest degradation and considerably higher future costs associated with forest restoration. Uses C. orbiculatus favourable ornamental qualities, particularly its colourful and abundant fruit, make it an attractive ornamental species. Geographical range Native range: Asia (USDA-GRIN, 2004). Known introduced range: Australasia-Pacific and North America (Dreyer, 2003; USDA-GRIN, 2004). Introduction pathways to new locations For ornamental purposes: McNab and Loftis (2002) state that oriental bittersweet was introduced as an ornamental to the USA. Local dispersal methods Consumption/excretion: McNab and Loftis (2002) state that, "Seeds are believed to be disseminated primarily by birds ( Stoll et al. 1980 and Dreyer, 1994) that consume the leathery capsule consisting of three to five seeds, which ripens in the fall." People sharing resources (local): Management information For details on preventative measures, chemical, physical, biological control options, please see management information. Reproduction McNab and Loftis (2002) state that, "Seeds are believed to be disseminated primarily by birds ( Stoll et al. 1980 and Dreyer, 1994) that consume the leathery capsule consisting of three to five seeds, which ripens in the fall." Lifecycle stages McNab and Loftis (2002) recorded in their study that, " C. orbiculatus vines emerged from winter dormancy and began stem elongation several weeks before the arborescent overstory. We observed that many C. orbiculatus seedlings from 0.2 to 0.5m height had experienced periodic dieback of the stem terminal followed by resprouting. Paterson (1975) reported that tip ends of C. orbiculatus stems are typically killed by onset of freezing temperatures in the fall and although not reported, susceptibility of seedlings to cold damage could be influenced by their location in relation to canopy gaps." Silveri et al. (2001) state that, "In the absence of disturbance, C. orbiculatus invades forested habitat using a strategy similar to the 'advance regeneration' of some canopy trees. Like these shade tolerant species (Philips and Shure 1990; White 1991), C. orbiculatus seedlings may persist for long periods on the forest floor but require creation of a gap to reach the canopy and reproduce sexually." Reviewed by: Dr. Robin Harrington. Associate Professor, Department of Natural Resources Conservation. University of Massachusetts. USA Principal sources: Dreyer, 2003. Element Stewardship Abstract For Celastrus orbiculatus Thunb. (C. articulatus) McNab and Loftis, 2002. Probability of occurrence and habitat features for oriental bittersweet in an oak forest in the southern Appalachian mountains, USA. Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG) with support from the Terrestrial and Freshwater Biodiversity Information System (TFBIS) Programme (Copyright statement) Last Modified: Thursday, 15 December 2005