Alternanthera philoxeroides (Mart.) Griseb.

Title: Alternanthera philoxeroides (Mart.) Griseb.

Scientific Name:

Alternanthera philoxeroides (Mart.) Griseb.

Common Names:

alligator weed

Source & more images (via ALA)

Habitat: Warm-temperate to tropical regions in wet waste places and water in swampy mud flats (Parsons and Cuthbertson 1992). Alligator weed thrives in shallow drainage ditches, canals, rivers, lakes, reservoirs, swamps, rice fields, and wet or occasionally inundated pastures (Parsons and Cuthbertson 1992).

Distribution:

Original source via CABI

Invasiveness Assessment

ESTABLISHMENT

1. Germination requirements? “Growth (vegetative) starts with development of node buds on old stems in early spring”. (Parsons and Cuthbertson, 1992)

2. Establishment requirements? “Establishes readily wherever there is an adequate water supply…it has a low light requirement”. (Parsons and Cuthbertson, 1992)

3. How much disturbance is required? Established in rice crops and inundated pastures. (Parsons and Cuthbertson, 1992)

GROWTH / COMPETITIVE

4. Life form? Aquatic (emergent or free flowing) as well as terrestrial. (Parsons and Cuthbertson, 1992)

5. Allelopathic properties? None reported.

6. Tolerates herb pressure?

7. Normal growth rate? “Strong competition in rice fields and pastures prone to water logging, often crowding out desirable species”. “Alternanthera philoxeroides competes successfully with other plants with the exception of water hyacinth. (Spenser & Coulson 1976); (Coulson 1977); (Julien & Broadbent 1980 p. 154). ( Parsons and Cuthbertson, 1992)

8. Stress tolerance to frost, drought, w/logg, sal. etc? Tolerant of frosts, water logging and salinity. “It requires a warm growing season but will tolerate cold winters including severe frosts which may kill emergent stem material. (Coulson 1977)”. (Julien & Broadbent 1980 p. 152.) (Parsons and Cuthbertson, 1992)

REPRODUCTION

9. Reproductive system? “Reproduction in the field is entirely vegetative”. (Parsons and Cuthbertson, 1992)

10. Number of propagules produced? “Reproduction in the field is entirely vegetative”.

11. Propagule longevity?

12. Reproductive period? Produces thick mats. (See picture P & C 1992 p. 157).“Floating mats of alligator weed are generally monocultures”. (Julien & Broadbent 1980 p. 152). (Parsons and Cuthbertson, 1992)

13. Time to reproductive maturity? Nodes on old stems in early spring stems and flowers in mid summer - flowering until March. Some seeds produced but rarely ever viable in Australia (Parsons and Cuthbertson, 1992).

DISPERSAL

14. Number of mechanisms? Water currents and cultivation. (Parsons and Cuthbertson, 1992)

15. How far do they disperse?

Impact Assessment

RECREATION

1. Restrict human access? Prostrate, semi-prostrate or ascending plant in both terrestrial and aquatic situations. Restricts access on land and can seriously affect access to waterways. (Parsons and Cuthbertson, 2001)

2. Reduce tourism? “In water dense mats…extend for 15 m or more.” Major impact on water-based recreation and creates a dangerous hazard for swimming. (Ensbey, 2001; Muyt, 2001)

3. Injurious to people? Not toxic through physical contact. The plant has been cultivated and consumed in Australia in the mistaken belief it is the culinary herb A. sessilis, known commonly as Mukunu-wenna. The plant does contain calcium oxalate crystals. (Muyt, 2001; Parsons and Cuthbertson, 2001)

4. Damage to cultural sites? An “aggressive, invasive species.” In terrestrial situations it develops extensive root systems and is very persistent. Infestation could seriously affect historic or cultural feature. In attempting to eradicate the weed extensive excavation may need to be undertaken. (Muyt, 2001)

ABIOTIC

5. Impact flow? “The prolific growth restricts flow, increases sedimentation, aggravates flooding and acts as a barrier.” (Groves et al., 1995)

6. Impact water quality? “…the thick mats…restrict light penetration…and create anaerobic conditions.” “The mats restrict light, thereby reducing primary productivity and anoxic conditions may result.” (Groves et al., 1995; Parsons and Cuthbertson, 2001)

7. Increase soil erosion? Terrestrial plants have thickened, dense roots to depths of 0.5 m. Soil erosion not increased as a result of infestation. (Muyt, 2001)

8. Reduce biomass? In aquatic situations biomass is increased significantly. Little effect in terrestrial situations. (Groves et al., 1995)

9. Change fire regime? In both aquatic and terrestrial situations the plant does not die back leaving dry matter to support fire. (Gunaseker pers. comm)

COMMUNITY HABITAT

10(a) Impact on composition of high value EVC? EVC=Plains Grassy Wetland (E); CMA=Port Phillip; Bioreg:= Central Victorian Uplands; VH CLIMATE potential. Although not known as an invasive weed in Victorian natural ecosystems, it has the potential to invade riparian vegetation, freshwater wetland (seasonal and permanent). “It has a low light requirement.” In aquatic situations it has the capacity to form monocultures, but less so on land. (Groves et al., 1995; Parsons and Cuthbertson, 2001)

10(b) Impact on medium value EVC? EVC=Sedgy riparian woodland (D); CMA= Port Phillip; Bioreg:= Central Victorian Uplands; VH CLIMATE potential. Similarly invasive as above. (Groves et al., 1995; Parsons and Cuthbertson, 2001)

10(c) Impact on low value EVC? EVC=Wet forest (LC); CMA= Port Phillip; Bioreg:= Central Victorian Uplands; VH CLIMATE potential. As in 10(a). (Groves et al., 1995; Parsons and Cuthbertson, 2001)

11. Impact on structure? “Floating mats of A. philoxeroides are generally monocultures but other species occur close to the bank. In wet terrestrial situations, it may occur as the only emergent species but is more often associated with clover, grasses or common rush.” (Groves et al., 1995)

12. Effect on threatened flora?

FAUNA

13. Effect on threatened fauna?

14. Effect on non-threatened fauna? Due to its invasive habit in waterways and its potential to create anoxic conditions, it is likely to reduce the habitat and threaten aquatic fauna. “…affects fish and other organism habitat.” (Groves et al., 1995; Blood, 2001)

15. Benefits fauna? “Alligator weed provides no benefits to Australia.” (Groves et al., 1995)

16. Injurious to fauna? No evidence of harm to fauna although, “In New Zealand and Australia alligator weed causes photosensitisation of skin in light pigmented cattle resulting in cancerous lesions.” (Ensbey, 2001)

PEST ANIMAL

17. Food source to pests? Not evident, but some herbivorous insects do feed on plant.(Groves et al., 1995)

18. Provides harbor? May provide harbour for minor pest species (birds). (Groves et al., 1995)

AGRICULTURE

19. Impact yield? It is a strong competitor in rice fields and pastures prone to waterlogging. “Alligator weed has eliminated small crops and turf farming from parts of the Lower Hunter (NSW).” (Parsons and Cuthbertson, 2001; Ensbey, 2001)

20. Impact quality? “If present, land and associated production can be quarantined and sales restricted due to W1 weed status.” (Ensbey, 2001)

21. Affect land values? As above.

22. Change land use? In terrestrial situations it is difficult to eradicate. The plant is resistant to herbicide treatment and mechanical removal is difficult due to the depth of the root system. Excavation of up to 2 m is recommended. Significant change to use is dictated. See also comment in Q21 above.

23. Increase harvest costs? Occurrence of the weed in water supplies for irrigation and the need to control it can increase production costs. (Ensbey, 2001)

24. Disease host/vector? “Provides habitat for disease vectors such as mosquitoes.” (Blood, 2001)

Feedback

Do you have additional information about this plant that will improve the quality of the assessment? If so, we would value your contribution.

Assessment ratings originally made by the Victorian Department of Primary Industries.

The entry of this assessment was made possible through the generous support of an anonymous donor.

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referenced by (1)

wra702: Common Name - A (via alligator weed)

Article: wra1259 (permalink)
Categories: :wra:a, :wra:inv1, :wra:invmh, :wra:inv2, :wra:invh, :wra:inv3, :wra:inv4, :wra:inv5, :wra:invl, :wra:inv6, :wra:invm, :wra:inv7, :wra:inv8, :wra:inv9, :wra:inv10, :wra:inv11, :wra:inv12, :wra:inv13, :wra:inv14, :wra:inv15, :wra:imp1, :wra:imph, :wra:imp2, :wra:imp3, :wra:impml, :wra:imp4, :wra:imp5, :wra:imp6, :wra:imp7, :wra:impl, :wra:imp8, :wra:imp9, :wra:imp10a, :wra:impmh, :wra:imp10b, :wra:imp10c, :wra:imp11, :wra:imp12, :wra:impm, :wra:imp13, :wra:imp14, :wra:imp15, :wra:imp16, :wra:imp17, :wra:imp18, :wra:imp19, :wra:imp20, :wra:imp21, :wra:imp22, :wra:imp23, :wra:imp24
Date: 23 September 2009; 11:09:03 AM AEST

Author Name: David Low
Author ID: adminDavid