Alligator weed
Alternanthera philoxeroides
family
Amaranthaceae
origin
Exotic
declaration
Category 3 Restricted Matter (Biosecurity Act 2014)
Must not be distributed or disposed. This means it must not be released into the environment unless the distribution or disposal is authorised in a regulation or under a permit.
Common names
Alligator weed, Alligatorweed, Mukuna-menna, Pannankarni.
A semi-aquatic, aquatic, or terrestrial herbaceous plant that produces roots at its stem joints. These stems are often hollow when growing in water, and form dense mats of vegetation out over the water surface. Its oppositely arranged leaves are almost stalkless and elongated in shape (2-14 cm long and 1-4 cm wide). Its flowers are borne in dense globular clusters (1-2 cm across) on stalks 2-9 cm long in the forks of the upper leaves.These small flowers have five white 'petals' that acquire a papery appearance as the fruit mature.
Impact
Impact
Alligator weed (Alternanthera philoxeroides) is already an important environmental weed in New South Wales, Victoria and Queensland, and is seen as a potentially significant environmental weed in many other parts of Australia. It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. In fact, this species has been named as one of Australia's 20 Weeds of National Significance (WoNS). It is thought that the potential range of alligator weed (Alternanthera philoxeroides) includes waterways throughout most of southern and eastern Australia.It is an especially troublesome weed because it invades both terrestrial and aquatic habitats, and is very difficult to eradicate. Alligator weed (Alternanthera philoxeroides) can totally disrupt natural aquatic ecosystems by blanketing the surface of the water with thick mats of vegetation that impede the penetration of light below the water surface, shading out any submerged native plant species. These mats also promote sedimentation and flooding and prevent gaseous exchange, leading to a reduction in water quality (i.e. reduced oxygen levels in the water). Such changes to aquatic ecosystems can have significant negative impacts on the native plants and animals growing in them (e.g. reduce water bird and fish activity, cause the death of native fish and replace native wetland plants). When growing on land it also grows into a dense mat of vegetation with a mass of creeping underground stems (i.e. rhizomes) and is capable of out-competing all but the most robust plant species. It quickly displaces native plants and can be harmful to the native animals that rely on them.Alligator weed (Alternanthera philoxeroides) is currently having the greatest impact in New South Wales, where the total infested area is now estimated at 3,950 hectares. It has spread from initial sites in the Newcastle area to invade aquatic habitats and seasonally flooded land in the Fullerton Cove, Williamtown and Raymond Terrace areas in the Lower Hunter region. In the Sydney region, alligator weed (Alternanthera philoxeroides) has spread throughout the Parramatta and Georges River catchments. It has also spread to many other locations in the Sydney basin including the Botany wetlands, several northern suburbs and the Hurstville area. However, its continual spread downstream in the Hawkesbury/Nepean catchment, which now has approximately 70 km of infested waterways, in of most concern in this region. Large infestations have also bee located in Barren Box Swamp, near Griffith, and in a tributary of the Richmond River, on the far north coast.It should also be noted that alteration to the natural flow regimes of rivers, streams, floodplains and wetlands has been listed as a "key threatening process" to natural ecosystems in New South Wales. Exotic plant species such as alligator weed (Alternanthera philoxeroides) have reduced stream flows and substantially contributed to this worsening environmental problem (i.e. by impeding water flow and increasing water loss through transpiration). Alligator weed (Alternanthera philoxeroides) has also been found at several hundred sites in Victoria, though most of these sites are in backyards in suburban Melbourne. It is listed among the top 50 most invasive plant species in south-eastern Queensland, even though it is not yet widely naturalised in this region. This species is also regarded as a potentially invasive garden plant in the Greater Adelaide region and is considered to to pose a significant threat to Adelaide's biodiversity.Alligator weed (Alternanthera philoxeroides) is also very invasive overseas, and is considered to be one of the worst aquatic weeds in the world. In the USA, it forms dense tangled mats of vegetation that overtop native aquatic plants and out-compete them for sunlight. It eventually replaces desirable native species and can significantly alter the aquatic and riverine ecology of heavily infested areas. This species also invades drains, streams, swamps and similar wet habitats in New Zealand and is noted to be harmful to native biodiversity in China. It is also a major problem parts of southern Asia (i.e. in Burma, Thailand, Indonesia and India). For more information from the Queensland Government
Location
Location
Characteristics
Characteristics
Similar Species
Similar Species
Alligator weed (Alternanthera philoxeroides) is already an important environmental weed in New South Wales, Victoria and Queensland, and is seen as a potentially significant environmental weed in many other parts of Australia. It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. In fact, this species has been named as one of Australia's 20 Weeds of National Significance (WoNS). It is thought that the potential range of alligator weed (Alternanthera philoxeroides) includes waterways throughout most of southern and eastern Australia.It is an especially troublesome weed because it invades both terrestrial and aquatic habitats, and is very difficult to eradicate. Alligator weed (Alternanthera philoxeroides) can totally disrupt natural aquatic ecosystems by blanketing the surface of the water with thick mats of vegetation that impede the penetration of light below the water surface, shading out any submerged native plant species. These mats also promote sedimentation and flooding and prevent gaseous exchange, leading to a reduction in water quality (i.e. reduced oxygen levels in the water). Such changes to aquatic ecosystems can have significant negative impacts on the native plants and animals growing in them (e.g. reduce water bird and fish activity, cause the death of native fish and replace native wetland plants). When growing on land it also grows into a dense mat of vegetation with a mass of creeping underground stems (i.e. rhizomes) and is capable of out-competing all but the most robust plant species. It quickly displaces native plants and can be harmful to the native animals that rely on them.Alligator weed (Alternanthera philoxeroides) is currently having the greatest impact in New South Wales, where the total infested area is now estimated at 3,950 hectares. It has spread from initial sites in the Newcastle area to invade aquatic habitats and seasonally flooded land in the Fullerton Cove, Williamtown and Raymond Terrace areas in the Lower Hunter region. In the Sydney region, alligator weed (Alternanthera philoxeroides) has spread throughout the Parramatta and Georges River catchments. It has also spread to many other locations in the Sydney basin including the Botany wetlands, several northern suburbs and the Hurstville area. However, its continual spread downstream in the Hawkesbury/Nepean catchment, which now has approximately 70 km of infested waterways, in of most concern in this region. Large infestations have also bee located in Barren Box Swamp, near Griffith, and in a tributary of the Richmond River, on the far north coast.It should also be noted that alteration to the natural flow regimes of rivers, streams, floodplains and wetlands has been listed as a "key threatening process" to natural ecosystems in New South Wales. Exotic plant species such as alligator weed (Alternanthera philoxeroides) have reduced stream flows and substantially contributed to this worsening environmental problem (i.e. by impeding water flow and increasing water loss through transpiration). Alligator weed (Alternanthera philoxeroides) has also been found at several hundred sites in Victoria, though most of these sites are in backyards in suburban Melbourne. It is listed among the top 50 most invasive plant species in south-eastern Queensland, even though it is not yet widely naturalised in this region. This species is also regarded as a potentially invasive garden plant in the Greater Adelaide region and is considered to to pose a significant threat to Adelaide's biodiversity.Alligator weed (Alternanthera philoxeroides) is also very invasive overseas, and is considered to be one of the worst aquatic weeds in the world. In the USA, it forms dense tangled mats of vegetation that overtop native aquatic plants and out-compete them for sunlight. It eventually replaces desirable native species and can significantly alter the aquatic and riverine ecology of heavily infested areas. This species also invades drains, streams, swamps and similar wet habitats in New Zealand and is noted to be harmful to native biodiversity in China. It is also a major problem parts of southern Asia (i.e. in Burma, Thailand, Indonesia and India). For more information from the Queensland Government
