Arum Lily (Zantedeschia aethiopica)

Photo: (c) Tony Hisgett

Family: Araceae

Growth Habit: Group of dark green, large leaves arising on fleshy stalks annually from perennial tuberous roots. Leaves are shiny, somewhat succulent, smooth, leathery, arrow shaped and large, 130-500 mm long and 80- 250 mm wide. The first leaves are similar to mature leaves but only 10-20 mm tall. Tuber like rhizomes gives rise to white, fleshy, finely branched, 3 mm thick laterals. Rhizomes are usually a dense cluster of several large, knobbly, short, thick tubers and many small tubers. Flower stalks are erect, stout and arise from the base of the plant up to 1 m tall.

Type of Plant: A robust, dark green, succulent herb

Photo: (c) Franco Folini CC-BY-SA-2.0 license.

Flowers: The false flower or spathe is large white to greenish white and tubular, becoming funnel shaped at the top with a slit down one side. The spathe surrounds the orange-yellow spike of flowers. Flowering takes place in spring. Numerous tightly packed male and female flowers. Upper Male section is covered with stamens and 4 times longer than the lower female section.

Fruits/Seeds: The berry is oval, yellowish, about one centimetre in diameter and contains 4 yellow-brown round seeds about three millimetres in diameter.

Dispersal: By seeds and rhizomes. Initially spread through garden escapees and dumping or garden waste. Spread by seeds and rhizomes once established. Spread into new areas by seeds eaten by birds and mammals or carried by water along creaks and irrigation channels. Rhizome fragments readily establish when moved by cultivation or earthworks.

Distribution: Weed of pastures, disturbed areas, vegetables, roadsides, streams and watercourses, recreational areas, bush land (and especially urban bush land), irrigation channels, freshwater wetlands, gardens and rubbish dumps.

Status: Not declared in Tasmania but has the potential to be a significant environmental weed, especially in waterways, wetlands,  damp spots and coastal areas. The green form called ‘Green Goddess’ is also invasive and can be found clogging up natural waterways.

Arum Lily spreading in Melaleuca wetland, Trevallyn.

Weed Impacts:

  • All parts of the Arum Lily are toxic humans and livestock. Contains toxic amounts of Calcium Oxalate.
  • Engulfs gutters, streams, waterways and wetlands, smothering native vegetation and changing waterflows.
  • Can produce a monoculture of Arum Lily in the understorey.
  • Impedes water and may cause local flooding.
  • Competes with perennial pasture plants.
  • Stock deaths have occurred from grazing Arum Lily.

Control Methods:

  • Grow me instead – replace Arum Lily’s in your garden with species such as Purple Flag Iris (Patersonia occidentalis), Sagg (Lomandra longifolia) and  Calla Lilies (Zantedeschia elliottiana and rehmannii, although closely related they are not regarded as invasive).
  • Manual Removal. Dig out when soil is moist. Ensure to remove all the roots and bulbs as these will reshoot.
  •  Cultivation. This can be useful if done over a few years.
  • Herbicide. Chlorsulfuron and metsulfuron provide good levels of control provided they are applied before the flowers start to wither. Annual, winter applications of 2,4-D provide good control in about 3 years. Paraquat and Diquat also provide good control if repeated. Glyphosate is relatively ineffective.

N.B. Always check the herbicide label before use.