Description
Barleria (Barleria prionitis) is a robust prickly shrub to 1.5 m tall. Its branches are hairless and have 2-5 spines each 10 -20 mm long at the base of leaves and branches. Its leaves are oval in shape and up to 130 mm long and 40 mm wide. The edges of the leaves are smooth but the apex is spine-tipped. Hairs may be found either all over the leaf or only on the midrib, edges and main lateral veins.
The yellow-orange, tubular flowers are about 40 mm long and grow in bunches at the ends of branches, sometimes with some single flowers at the leaf bases below. Each flower has a leaflike bract and a pair of spreading spines at its base. There are 4 stamens but only 2 of them protrude beyond the petals. The seed capsules are about 18 mm long, hairless and contain 2 flat seeds, measuring about 8 mm by 5 mm. The seeds are covered in long hairs which becoming mucilaginous when wet.
For further information and assistance with identification of Barleria contact the herbarium in your state or territory.
Distribution:
Barleria was originally recorded in the Northern Territory in Darwin and from the Victoria River Downs Station area where it probably arose from discarded pot plants. It has also been found around Berry Springs, Katherine and Mataranka. The population from waste places on the Ross River in Townsville has apparently now been eradicated, but the Victoria River Downs plants persist. Barleria is also recorded in the East Kimberley in Western Australia and on Boigu Island in the Torres Strait.
Barleria is well adapted for the wet-dry tropics of northern Australia and has the potential to spread throughout that region.
Habit:
Shrub
Key points:
- The dense prickly thickets which Barleria (Barleria prionitis) forms are undesirable for economic and environmental reasons.
- Because it escapes from gardens, other species should be planted instead.
- Barleria is difficult to eradicate once established, but early intervention is effective.
- It has medicinal and antiseptic properties which may be able to be exploited if the plant continues to spread.
- If you see a plant that may be Barleria, contact your local council or state territory weed management agency.
How it spreads:
Dispersal is by seeds, 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. 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. As with most members of the family Acanthaceae, mature capsules explode and fling out their seeds; the signal to do this is often wetting of the capsule after a dry period.
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. Because of the ability of Barleria to grow roots from any node of the plant care needs to be taken that garden waste is treated before it is discarded. All known occurrences in Australia appear to have been from discarded garden plants.
Where it grows:
Barleria grows on a wide variety of soils and seems to prefer well-drained areas. In the Katherine area it has been recorded from rugged limestone outcrops in very little soil, presumably extracting moisture by a network of roots into rock crevices. It occurs in savanna country, along river banks and, on Boigu Island, in sand. It is also recorded from disturbed areas such as roadsides or overgrazed pastures.
Flower colour:
Yellow
Distribution map:
Impacts:
Barleria is on the Alert List for Environmental Weeds, a list of 28 non-native plants that threaten biodiversity and cause other environmental damage. Although only in the early stages of establishment, these weeds have the potential to seriously degrade Australia’s ecosystems.
Barleria is found in natural ecosystems, such as open woodland or along watercourses, in the Northern Territory, where it can be very persistent and difficult to remove. While it is not particularly active in the dry season it becomes extremely vigorous with the onset of the wet.
The dense, prickly thickets that it eventually forms are potentially environmentally and economically damaging. Cattle do not eat Barleria, and their movements, as well as those of other animals, may be impeded where it occurs around waterways. It can also provide refuges for feral animals. Clearly it is not desirable in areas of human recreation and may reduce the capacity for indigenous people to exploit natural resources in infested areas.
Origin:
Barleria occurs naturally throughout East Africa, tropical Asia, including India, Indonesia, Malaysia and the Philippines. It is a weed in parts of tropical America (Puerto Rico) and in Hawaii (Francis, undated).
Most recorded infestations in Australia have been traced back to escapees from gardens. Barleria was originally recorded in Northern Territory at Darwin and in the Victoria River Downs Station area where it probably arose from discarded pot plants in the area surrounding the old 1920s hospital on Wickham River. A population from waste places on the Ross River in Townsville has apparently now been eradicated, but the Victoria River Downs plants persist, though under “active control” (Waterhouse 2004, pers. comm.). Barleria has escaped into a creek at Argyll Diamonds in the East Kimberley (Mitchell 2004, pers. comm.). A small naturalised population originating from dumped garden plants occurring on a sand spit on Boigu Island in the Torres Strait appears to be spreading.
History:
The date of Barleria’s original arrival in Australia is not known. Because of its wide use as an ornamental and hedge plant and the establishment of the Victoria River Downs populations from discarded pot plants by the 1960s it is likely that it was introduced to Australia at least by the early 1900s.
It is used as a hedge plant. It is also possible that it may have been introduced to Australia because of its well known medicinal and antiseptic properties, including treating fever, respiratory diseases, tooth ache, joint pains and a variety of other aliments.
