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Zantedeschia aethiopica

Description
 

Arum Lily (Zantedeschia aethiopica) is a robust, clump-forming, perennial herb growing to 1.5 m high. It has a stout rootstock or short, thick underground stem (rhizome) with white, somewhat fleshy, finely branched roots. There is often a dense cluster of several large, knobbly tuber-like rhizomes and many smaller tuber-like nodules (rhizomatous offsets). The large arrowhead-shaped leaf blades are glossy dark green to somewhat dull, leathery in texture, to 60 cm long and 30 cm wide, with a prominent midrib and a tip that is bent downwards or curls towards the underside of the leaf. Arising directly from the basal rhizome, the thick, fleshy leaf stalks are up to about 80 cm long, narrowly winged at their base, and exude a sticky sap when broken (Jessop 1986; Hay 1993; Conn 1994; Curtis & Morris 1994; Moore 1997; Parsons & Cuthbertson 2001; Sainty & Associates 2003).

The arum-type flower structure has a central spike (the spadix) to 9 cm long bearing tiny, tightly packed pale yellow to orange-yellow flowers (male flowers above, female below). This is surrounded by a white to ivory (sometimes with green shading) funnel-like bract (the spathe) to 26 cm long terminating with a pointed, recurved tip. The spathe is split to the base on one side with overlapping edges spreading in the upper part. The thick and fleshy flower stalk is as long as or slightly longer than the leaves (Jessop 1986; Hay 1993; Conn 1994; Curtis & Morris 1994; Moore 1997; Parsons & Cuthbertson 2001; Sainty & Associates 2003).

The fruits are irregularly globular berries, 5-10 mm long, clustered in the lower part of the central spike. The immature berries are green or yellowish, turning orange when ripe. They contain several to sometimes many yellowish brown or yellowish orange seeds that are about 3 mm in diameter (Jessop 1986; Hay 1993; Conn 1994; Curtis & Morris 1994; Moore 1997; Parsons & Cuthbertson 2001; Sainty & Associates 2003).

For further information and assistance with identification of Arum Lily contact the herbarium in your state or territory.

Distribution:

Arum Lily is naturalised in temperate regions of Australia. It is found from Northampton to Esperance in south-western Western Australia; in south-eastern South Australia (e.g. moist valleys in the Adelaide Hills); in coastal eastern New South Wales (mainly south from Gosford), southern Victoria and Tasmania (mainly north-west area). It has also been reported as a garden escape near urban areas of Brisbane in south-eastern Queensland (Hay 1993; Keighery 1997; Scott 1997a; Parsons & Cuthbertson 2001; Groves et al. 2005).

Arum Lily is well adapted to the Mediterranean climate of south-western Australia, where it grows and spreads vigorously. It is a particularly serious weed along creek lines and in wet areas, pastures and natural bushland (Keighery 1997; Plummer 1997; Scott 1997a; Sainty & Associates 2003).

Arum Lily has not become widely naturalised in any other region of the world, despite being grown around the world as an ornamental (Scott 1997a). It is a localised weed in New Zealand, Norfolk Island, China, Africa, Mascarenes, Europe, Azores, Canary Islands, Madeira, and the United States (Scott 1997a, Blood 2001, Weber 2003).

Habit:Herb
Key points:
  • Arum Lily (Zantedeschia aethiopica) is a tall fleshy herb with big, dark green, arrowhead-shaped leaves and large white funnel-shaped 'arum-type' flower structures with a central yellow spike.
  • It is a common ornamental garden plant that has escaped from cultivation.
  • Arum Lily has become a widespread weed, invading mainly damp habitats in pastures, wetlands and forest.

All parts of the plant are toxic to humans, stock and pets.

How it spreads:

Arum Lily spreads by both seed and root fragments (Weeds Australia undated).

There may be 50-500 seeds per flower head and up to 5 000 seeds per square metre in a dense stand of plants. The seeds germinate readily, though they do not usually remain viable for more than about 4 months. The seeds are spread by water, birds, foxes, livestock, contaminated soil, machinery, and in dumped garden waste (Panetta 1988; Moore 1997; Plummer 1997; Uren 2000; Blood 2001; Parsons & Cuthbertson 2001; Sainty & Associates 2003 WEEDeck H10).

Natural spread by rhizome growth or expansion is usually localised and less than 30 cm per year (Moore 1997). However, the plant can be spread rapidly from initial sites of introduction by rhizome fragments, which can travel long distances through garden refuse disposal, cultivation and earthworks.

Where it grows:

Arum Lily is naturalised in many parts of southern Australia. It grows in open to semi-shaded conditions in damp or marshy areas in wasteland, rubbish dumps, abandoned habitation sites, pastures, market gardens, freshwater wetlands, disturbed creeklines, waterways (commonly on stream banks), floodways, drains, gullies and irrigation ditches as well as in bushland, warm-temperate rainforest and sand dune heath (Sainty & Jacobs 1981; Scott & Wykes 1997a; Blood 2001; Parsons & Cuthbertson 2001; Sainty & Associates 2003; Richardson et al. 2006). Keighery (1997) describes in more detail the range of habitats and locations invaded by Arum Lily in Western Australia.

Arum Lily prefers subtropical to temperate climates but has a wide tolerance: tropical to cold areas, sun to shade conditions, frost to -10oC (if less than five days of frost per year), water-logging for short periods with up to 30 cm of water over the rootstock, wind, and salt (Blood 2001). Its distribution inland may be limited by frost. It thrives in sandy soil with a periodically high watertable (Sainty & Associates 2003) but also commonly occurs on rich friable soils (Parsons & Cuthbertson 2001).

Flower colour:White, Yellow
Distribution map:

http://www.weeds.crc.org.au/documents/arumlily.pdf 

Impacts:

Arum Lily was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Arum Lily was not included as one of the 20 WONS. However, it remains a weed of potential national signficance.

Arum Lily can form large spreading clumps. It is a problem for agriculture where it competes with pasture - dense infestations can completely replace pasture species (Parsons & Cuthbertson 2001) - and is a health hazard for stock, being especially toxic to cattle (Groves et al. 2005).

However, it is increasingly being recognised as a significant environmental weed, which invades native vegetation and achieves dominance along watercourses and swampy habitats (Scott & Wykes 1997a). Dense clumps of Arum Lily crowd out native species affecting the biodiversity of natural areas, especially by replacing the native understorey. In wet, swampy habitats it can be extremely troublesome as it impedes water flow (Hussey et al. 1997).

The tuber-like roots and rhizomes, leaves, flowers (especially the yellow spike), fruit and seeds are poisonous, as well as being a skin and eye irritant to humans, livestock and pets (Shepherd 2004; Lloyd & Dodd 2006; Richardson et al. 2006). It can cause eczema and irritant dermatitis (Shepherd 2004). The plant has caused fatalities in humans and stock and is especially toxic to children (Parsons & Cuthbertson 2001; Sainty & Associates 2003). Symptoms of poisoning include swelling and burning of the lips, mouth, throat and tongue, acute gastritis (stomach pain) and diarrhoea, causing exhaustion, shock and death (Lamp & Collet 1989; Parsons & Cuthbertson 2001; Shepherd 2004; Lloyd & Dodd 2006). Toxicity is due to calcium oxalate and the alkaloid coniine (Shepherd 2004).

Further information on poison properties and poisoning is provided by Aplin (1966), Everist (1964, 1974), Covacevich et al. (1987), the Child Accident Prevention Foundation of Australia and the U.S. Food & Drug Administration Poisonous Plant Database.

Origin:

Arum Lily is native to Natal and Cape Province in South Africa (Scott & Wykes 1997a).

History:

Arum Lily was introduced to Australia as an ornamental plant for horticulture and was widely promoted in nursery catalogues in Victoria from the 1850s to 1880s. It was introduced into Western Australia by immigrants and floriculturists who were looking for plants suited to the Mediterranean climate of the area. Despite its potential as a significant weed, Arum Lily is still available from nurseries in many states as a garden plant, and is still popular in the florist trade, being traditionally associated with funerals (Groves et al. 2005).

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This database is designed to provide information, including biological and ecological, on invasive plant species that are on a national weed list, or are legislated against in a state or territory. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. For further information on the images contained in the database please contact the copyright owner. All images in the weed identification tool are managed by the Australian Plant Image Index (APII). Various copyright conditions apply for these images. For further information on the copyright conditions of images contained in the database please contact the APII at: photo@anbg.gov.au.