Barleria has spread into natural ecosystems from gardens and the improper disposal of garden waste. It has the potential to cause economic and environmental damage by forming dense thickets that displace native vegetation and prevent revegetation by native plants. Thickets can impede the movement of stock, restrict access to waterways and reduce the aesthetic values of natural bushland.
Barleria has some beneficial properties that undoubtedly have helped increase its distribution: it is used as a hedge plant; it has numerous medicinal properties including treating fever, respiratory diseases, toothache, joint pains and a variety of other ailments; and it has several cosmetic uses.
Barleria is native to tropical East Africa and Asia, including India, Indonesia, Malaysia and the Philippines. It has been cultivated throughout the world as an ornamental plant, and has escaped from gardens in many regions including Mauritius, Hawaii, Puerto Rico and Papua New Guinea.
Barleria has been found around townships in the Northern Territory (Darwin, Berry Springs, Katherine, Mataranka and the Victoria River district), Queensland (Townsville) and on Boigu Island in the Torres Strait. In 2002 it was discovered in the Kimberley Region of Western Australia. It has not been found in New South Wales but should be part of early detection protocols in northern parts of the state.
Barleria reproduces by seed, one plant producing up to hundreds of seeds in a season. It is not known how long the seeds remain viable in the soil after being dropped but it is likely to be at least several years. Seeds require moist conditions to germinate. Although most seeds germinate within a few metres of the parent plant, infestations can move relatively quickly downhill, where seed transport may be aided by water. Also, as seen in the Torres Strait infestation, seed spread may be quicker along paths or roads.
Many plants that are closely related to barleria are capable of vegetative reproduction when cuttings or stem fragments encounter a suitably moist environment that allows them to start growing roots. Barleria can probably also reproduce vegetatively.
Regardless of whether it has reproduced by seed or cutting, most recorded infestations in Australia have been traced back to escapees from gardens. It is thought that the Katherine infestations developed from garden waste that was dumped in bushland or transported on heavy machinery.
Barleria is an erect, prickly shrub, usually single-stemmed, growing to about 1.5 m tall. The stems and branches are stiff and smooth and light brown to light grey in colour. The leaves are up to 100 mm long and 40 mm wide, and oval-shaped though narrow at both ends (ellipsoid). The base of the leaves is protected by three to five sharp, pale coloured spines, 10–20 mm long.
The yellow–orange tubular flowers are found bunched tightly together at the top of the plant, but they also occur singly at the base of leaves. The flowers are 40 mm long and tubular, with several long protruding stalks (stamens).
The seed capsule is oval-shaped and 13–20 mm long, with a sharp pointed beak. It contains two fairly large, flat seeds, typically 8 mm long by 5 mm wide, covered with matted hairs. Barleria has a central tap root, with lateral roots branching off in all directions.
Barleria grows on a wide variety of soil types and seems to prefer well-drained soils. On the Australian mainland it grows well in tropical savanna country and along riverbanks. It is particularly hardy, and in the Katherine region flourishes on rugged limestone outcrops with little soil cover by clinging to the rocks and crevices with a network of roots. The small infestation on Boigu Island is growing on sandy soil. Barleria also grows well in disturbed areas such as roadsides or overgrazed pastures.
Barbara Waterhouse (AQIS/Weeds CRC), Andrew Mitchell (AQIS/Weeds CRC), Colin Wilson (NT DIPE), Noel Wilson (WA Dept of Agriculture), Peter James (Qld DNRM), Michael Crothers (NT Greening Australia), Bruce Morrow (Katherine) and John Thorp (National Weeds Management Facilitator).
CRC for Australian Weed Management (2003). Weed Management Guide: Barleria or porcupine flower. CRC for Australian Weed Management, Adelaide, South Australia.
Early detection and eradication are also important to prevent the spread of barleria. Small infestations can be easily eradicated if they are detected early but an ongoing commitment is needed to ensure new infestations do not establish.
Because there are relatively few barleria infestations, and it can potentially be eradicated before it becomes established, any new outbreaks should be reported immediately to your state weed management agency or local council. Do not try to control barleria without their expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem.
Barleria (Barleria prionitis) is not declared in NSW under the Noxious Weeds Act 1993.