A rhizomatous perennial with large, dark green, hairless, arrow shaped leaves to 50 cm long on stalks up to 3 metres tall. It usually grows in drains, water courses or very damp places.
Description:
Cotyledons:
One.
First leaves:
Leaves:
All basal.
Petiole - Up to 3000 mm long but usually less than 1000 mm, green to violet or reddish and attached near the centre of the lower half of the leaf. Hairless. Blade - Dark green,150-600 mm long by 125-225 mm wide, arrow shaped, soft texture. Notched at the base. Obvious network veins. Hairless. Ligule - None Auricles - None Stem leaves - None.
Stems:
None
Flower stem - Shorter than petioles, usually les than 1000 mm long.
Flower head:
Spike with many greenish white flowers. Male flowers on the lower portion, then sterile flowers then female flowers near the tip. Spike surrounded by a leaf like spathe.
Flower stalk (peduncle) usually shorter than petioles.
Uncommon in the south west of WA.
Flowers:
Spathe - 150-300 mm long, yellow with a green or red-purple base, sometimes curved.
Perianth - None.
Ovary - One celled with many ovules in 2-4 rows Stamens - Anthers -
Fruit:
Small berry.
Seeds:
Probably doesn't set viable seed in the south west of WA.
Roots:
Starchy, succulent, rhizomatous, upright tuber, up to 5000 g.
Old stands may have around 100 t/ha of tuber.
Smaller, globular cormels, 40-60 mm diameter, are produced on the sides of the tuber.
Stolons about 1000 mm long and 10 mm diameter.
Key Characters:
Hairless.
Large triangular leaves on a long stout petiole. Blade almost at right angles to the petiole.
Leaves prominently petiolate.
Spathe constricted, upper part yellow
Ovary one celled.
Biology:
Life cycle:
Perennial. Dormant in the cooler winter months in the south west of WA. Flowers are produced in autumn but are rarely seen and seed production is low and of low viability.
Physiology:
Tolerates long periods of inundation and waterlogging.
Reproduction:
By tubers, cormels and stolons. Seed is probably rare.
Flowering times:
Flowers not recorded in southern Australia.
Seed Biology and Germination:
Little viable seed produced.
Vegetative Propagules:
Tubers, stolons and cormels.
Hybrids:
There are a number of edible cultivars and varieties.
Allelopathy:
It is reported to inhibit the growth of companion plants.
Population Dynamics and Dispersal:
Spreads by stolons up to 1500 mm long that form new plants at their ends and cormels that that may be transported by water flows.
Spread is mainly by transport of tubers, cormels and stolons by earth moving equipment and dumping of garden refuse. Patches increase in size by about 1000 mm per year.
Origin and History:
Native to Indonesia and south east Asia. It may also be native to Northern Australia and Queensland.
Introduced to Beagle Bay Mission, near Broome in WA around the turn of the century.
Recorded as a weed of wetlands in Maylands, near Perth in 1982.
It is spreading along the Swan and Moore rivers.
Distribution:
ACT, NSW, QLD, NT, WA.
South East Asia, Lord Howe Island, Polynesia, Japan.
In water courses around the Perth region.
Habitats:
Climate:
Sub tropical to Mediterranean
It is most invasive in partial shade and permanently moist areas but will tolerate full sun to dense shade and long periods of inundation.
Soil:
Common on black sandy clays and slightly acid soils in wet areas. Prefers soils with much organic matter and high nitrogen levels.
Plant Associations:
Arum Lily, Water weeds.
Significance:
Beneficial:
Ornamental, tropical gardens.
Used in Asian and Polynesian cooking and has been cultivated for 6000 years.
Aboriginal food
Detrimental:
Weed of wet areas and water courses.
Forms thick stands that exclude most other species and can invade undisturbed wetlands.
Impedes water flow and may cause local flooding.
Toxicity:
Contains calcium oxalate at levels that may cause ill health in stock.
May cause a mild to severe rash in people.
Symptoms:
Skin rash and or mild sting when handling plants.
Treatment:
Legislation:
None.
Management and Control:
Don't dispose of rhizomes or garden waste in wetland areas. Reduce the quantities of nitrogen entering the infested area.
Control is often difficult because it often grows in boggy inaccessible areas.
Manual removal is difficult because of the large amount of root material present, regrowth from fragments that are left and disposal of the plants, tubers and cormels.
In areas with good access, removal of the plant and top 200 mm of soil with a backhoe and hand removal of fragments in following years should be effective.
Control with herbicides for a few seasons followed by manual removal of the odd remaining plants is probably the best strategy.
Little work has been done on chemical control. Sulfonylurea, bipyridyl and hormone herbicides are likely to be the best options for control.
Mowing, slashing and grazing are not effective.
Thresholds:
Eradication strategies:
Search for infestations upstream from the target area and control these first to reduce re infestation. Start with small satellite infestations and move into the main infestation.
Manual removal is effective provided all the tuber and cormels are collected and regrowth is removed the following season. Collected tubers and cormels can be composted at a dry site away from habitation because of the smell. Over a ton of plant material will need to be disposed of for each 100 square metres of infestation.
Alternatively mechanical removal of the tubers and top soil followed by hand removal of fragments for a few years should be effective.
Little work has been done and my best bet is to hand spray the leaves with a mixture of 10g chlorsulfuron(700g/kg) plus 250 mL wetting agent in 100 L water in summer before flowering. Repeat for 3 years then remove remaining tubers by hand.
Cutting the leaf close to the tuber and painting the cut with a mix of 1 L glyphosate(360g/L) plus 0.05 g metsulfuron(600g/kg) in 1 L water in late summer and then spraying emerging leaves 4 weeks later with a mix of 20 mL glyphosate(360g/L) plus 0.05 g metsulfuron(600g/kg) plus 2 mL Pulse Penetrant® in 1 L water has provided good control (Brown pers com). Odd remaining plants should be removed when seen over the next few years.
In early summer, it is difficult to use the cut stump method because of the copious quantities of sap that flows from the cuts.
Where large areas are controlled revegetation may be required to control stream bank erosion and colonisation by other wetland weeds.
Because this plant only appears to spread vegetatively, it should be possible to eradicate it quite successfully from local areas.
Herbicide resistance:
None recorded.
Biological Control:
None.
Related plants:
Arum Lily (Zantedeschia aethiopica) has a white, open spathe ("flower") and 3 celled ovary.
Plants of similar appearance:
References:
Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Brooks, K. and Brown, K. (2001) Managing Weeds in Bushland - Taro. EWAN (Inc), Perth.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P19.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #267.1.
Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P733.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.