Asparagus asparagoides: an invasive plant in Australia
Asparagus asparagoides, a very invasive climbing vine from the Asparagaceae family, was the topic of a workshop held in Australia on 2005-11-10/11. This plant is recognized as one of the most troublesome environmental weeds in southern Australia. Asparagus asparagoides (= Elide asparagoides) is naturalized in all Australian States, except in the Northern Territory and in the Australian Capital Territory (Canberra). It is most prevalent in the temperate and Mediterranean regions of southern Australia. Climate modelling to predict potential distribution of the plant showed that slight northern expansions could be expected along the east and west coasts of the mainland.
This plant is native to South Africa and was introduced into Australia as a garden ornamental possibly via Europe, where it was first used in horticulture. It is also recorded from Namibia and further north in tropical Africa. It naturalized in New Zealand where it is considered to be a weed, and in some counties of California (US). In the EPPO region, this plant is recorded in the Azores (PT) and mainland Portugal, Islas Canarias (ES), and Sicilia (IT). It is also known as an emerging invader in Corse (FR) (EPPO RS 2006/046). It can invade a variety of habitats in warm temperate climates. According to a climatic prediction, the plant has the potential to establish in the Mediterranean basin and along the Atlantic coast of the EPPO region (Portugal, France, United Kingdom and Northern Ireland) (Scott, pers. comm. 2006).
In Australia, it prefers shaded or partly-shaded habitat and grows in hind dunes on exposed beaches, coastal cliffs and amongst shrubs on sheltered bays. Mature plants contain, on average, two or three seeds. Frugivorous birds are recognized as important contributors to A. asparagoides seed dispersal. Whilst seeds remain the most important means of dispersal, established plants can also increase in size through spread of branching rhizomes. It is a major problem for conservation because it can change the structure, floristic composition and ecology of natural ecosystems. As a serious invader of both disturbed and undisturbed habitats, it can quickly dominate understorey vegetation, modify the aesthetics, affect access and change the overall structure of the landscape. It is also considered by citrus growers in Australia as one of the worst weeds they face. In fact, A. asparagoides has been rapidly invading citrus orchards causing decline, interfering with harvesting and tree maintenance operations and increasing production costs. This plant is prohibited from import to Australia under the Commonwealth plant quarantine legislation. Biological control agents have been released in Australia. Other management methods have been tested such as herbicides, hand weeding, slashing and grazing, fire and revegetation.
Sources
Plant Protection Quarterly (2006) Special National Asparagus Weeds Management Workshop Proceedings Part 1. Volume 21, Number 2. 88p.
Personal communication with John Scott, CSIRO Australia, 2006.
More information can be viewed on:
Weeds Australia: http://www.weeds.org.au/WoNS/bridalcreeper/