Arum Lily

Zantedeschia aethiopica (L.) Sprengel

Synonyms - Calla aethiopica, Richardia africana.

Family: Araceae.

Names:

Zantedeschia recognises the Italian botanist Dr Zantedeschi.
Aethiopica is Latin for Ethiopia and is in reference to Africa, its country of origin.
Arum Lily comes from its resemblance to plants in the Arum genus of lilies.

Other Names:

Calla Lily because it used to be in the Calla genus.
Childsiana
Death Lily
Funeral Flower
Green Goddess
Lily of the Nile
Pig Lily
Pink Marshmallow
Pink Mist
St Joseph's Lily
Varkblom (South Africa)
White Arum Lily

Summary:

Arum Lily has a tuft of dark green, shiny, somewhat succulent leaves arising annually from perennial tuberous roots. The large leaf blades are heart-shaped to arrow-shaped and usually about 250 mm long on a stalk almost as long. It is easily recognised by its conspicuous large, white, funnel-like 'flower' about 100 mm across, which has a central, orange, pencil-like column of minute male and female flowers. In fruit, the tiny female flowers at the base of this column are replaced by orange-yellow berries.
Native to South Africa, Arum Lily is a common and widespread serious weed of pasture and bushland, particularly of damp areas but also invading drier sites. It flowers mainly in late winter and spring and the berries are spread by birds.
This very distinctive plant is not likely to be confused with any native species.
It may be toxic to stock.

Description:

Cotyledons:

One.

First leaves:

Similar to mature leaves but only 10-20 mm tall.

Leaves:

Dark green, large, leathery and arrow shaped. Several per shoot arising from the base
Stipules - None.
Petiole - Green, becoming paler and white at the base. Sheathing near the base. 400 to 1500 mm long. Arises from the tuber like rhizome.
Blade - Arrow shaped (ovate-cordate), 130-500 mm long x 80-250 mm wide, shiny, smooth and wavy edges and blunt basal lobes. Base notched where the petiole joins. Tip pointed and bent down. Parallel, curved veins arising from the mid rib and indented into the upper surface of the leaf and raised on the lower surface. Sides curved to straight, angular and undulating. Surface flat to undulating.

Stems:

Short, fleshy rhizome.
Flower stalk - Erect, stout. Arises from the base of the plant. About 6 mm diameter and up to 1000 mm tall. Hairless.

Flower head:

Large, white, funnel shaped, erect, persistent spathe (leaf like bract), 100-260 by 80-150 mm, on a stout stalk. It is split to the base with overlapping edges, top widely spreading, tip pointed and bent back. Spathe surrounds the orange-yellow spike of flowers.
Spike or simple spadix - Bright yellow to orange-yellow, shorter than spathe but protrudes. On a stout stalk that extends to the base of the plant. Numerous tightly packed male and female flowers. Upper Male section is covered with stamens and 4 times longer than the lower female section.

Flowers:

Male and female flowers. Lower ones female, upper ones male. Yellow to orange. Small.
Ovary - 3 celled with 2 to many ovules in each cell.
Style - Short or absent.
Perianth - None.
Stamens - Stamens without anthers (staminodes) surround the female flowers.
Filaments - None.
Anthers - Yellow. Without stalks. Flat on top. Pollen forms thread like strings from pores at the top of the anther.

Fruit:

Globular, 5-10 mm diameter, succulent, berries in an enlarged cluster with about 40-50 berries. Initially green turning orange-yellow on maturity. 1-3 (rarely to 5) celled with few to 18 seeds and 4 on average.

Seeds:

Almost globular. Yellow-brown, 3 mm diameter. Wrinkled when dry.

Roots:

Tuber like rhizome gives rise to white, fleshy, finely branched, 3 mm thick laterals.
Rhizome is usually a dense cluster of several large, knobbly, short, thick tubers and many small tubers.

Key Characters:

Yellow spadix surrounded by a white, funnel shaped spathe.

Biology

Life cycle:

Perennial. Flowers mainly from August to December. Seeds germinate in autumn and winter and grow slowly producing a pea sized tuber by its first summer. It continues growth during summer if moisture is available and becomes dormant in early winter. New leaves form in winter to spring. It normally takes several years before it flowers. Nodules from tubers behave similarly and increase in size before flowering. Large tubers produce leaves in winter and spring and flower from late winter to spring each year. The flowering stem collapses and the spathe dries out as the seeds mature. Top growth normally dies off by mid to late summer and growth resumes in autumn.

Physiology:

Tolerates waterlogging up to 300 mm deep, a wide range of temperatures, sun and shade.
Tolerates occasional frost but it is not found in frost prone areas.

Reproduction:

By seeds and rhizomes.

Flowering times:

Any time but mainly June to December, with the major flowering from August to November. Flowering is often staggered.

Seed Biology and Germination:

(Based on Panetta, 1988)
Few seeds last longer than 4 months in the field and have little dormancy (Panetta, 1988). Up to 42% of seeds may be dormant soon after maturation but this drops to less than 7% within 15 weeks.
Viability declines rapidly during dry storage.
Large amounts of seed are produced (around 5000/m2 in dense stands). 50-500 seeds per flower head have been reported. More seed is produced at wet compared to drier sites.
They have optimum germination in alternating temperatures of 15-20oC during the day and 5-100C at night. Little germination occurs with temperatures of 27/35oC (i.e. in summer).
The seed is slow to germinate. It takes about 3 weeks after suitable temperatures and moisture are present before the first seeds germinate and another 3 weeks for the last seeds to germinate.
Seeds are not affected by exposure to light.
Removal of the outer layer of the testa caused most seeds to die before germination. This may be significant in determining the role of birds or other predators on the dispersal of the seed.
Low levels of fruit abortion and high levels of pollination and seed viability occur in the field.
Spraying plants with chlorsulfuron before anthesis completely stops seed production. Spraying before berry expansion allows some seed to develop but reduced seed viability to less than 1%. Spraying plants when berries had fully expanded had no effect on seed production or viability.
Plants cross pollinate because the pollen is shed before stigmas in the same flower head become receptive.

Vegetative Propagules:

Tuber like rhizomes with few to 30 or more tuber like offsets or nodules that are all capable of producing new plants.
Up to 100 t/Ha of rhizomes have been recorded in dense infestations (Moore, 1983).

Hybrids:

None.
A number of ornamental cultivars have been produced including Childsiana, Green Goddess, Pink Marshmallow and Pink Mist.

Allelopathy:

None reported.

Population Dynamics and Dispersal:

Initially it was spread by man as a garden plant and in garden refuse. Occasionally sold in nurseries and at fetes.
It is now mainly spread by seeds eaten by birds. Foxes and stock consume the seed and also aid dispersal. Birds are the main source of spread to new areas. The seed is short lived in the soil.
Seeds are carried in water flows along streams and irrigation channels.
Rhizome fragments readily establish when moved by cultivation or earthworks. Very localised spread (less than 300 mm/year) occurs by expansion of the rhizome.

Origin and History:

South Africa.

Distribution:

NSW, SA, TAS, VIC, WA.
12,000 Ha in WA spread over the Esperance plains, Geraldton sandplains, Jarrah forest, Swan coastal plain and Warren regions.
Weed of Azores, China, Corsica, Europe, Hawaii, Madeira, NZ, South Africa, USA

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Mediterranean. Sub humid and sub tropical regions with few frosts.
Warm temperate rainforests.
Occasional frost.

Soil:

Damp and poorly drained, friable soils.
Winter waterlogged areas.
Sandy, alkaline, coastal soils.
Rarely thrives on drier slopes.

Plant Associations:

Marsh, wetland coastal and riparian vegetation.

Significance:

Beneficial:

Ornamental. Reduces erosion.
Boiled roots are used for food by some African tribes.

Detrimental:

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.
Impedes water and may cause local flooding.
Listed as a "GardenThug".

Toxicity:

(Based on Everist, 1974)
Contains toxic amounts of Calcium Oxalate.
Cattle deaths have been reported but field problems are not common because stock generally avoid eating them.
Children have been fatally poisoned after eating the white spathe or yellow spadix of the flowers. This is probably due to an alkaloid in the flower and flower stalk. All parts of the plant are toxic and may cause illness if eaten.

Symptoms:

Swelling of the tongue and throat, acute gastritis and diarrhoea followed by death from shock and exhaustion. Irritates mucous membranes of the mouth and throat. Suspected of causing eczema.

Treatment:

Keep Arum Lily flowers out of reach of children.
See a doctor immediately if ingestion is suspected.

Legislation:

Noxious weed of WA.

Management and Control:

Mechanical removal is only effective if all the root fragments are removed. Multiple rotary hoeing over a few years as used in preparation for vegetable growing provides control. Chlorsulfuron (e.g. Glean®) and metsulfuron (e.g. Brush Off®) 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.

Thresholds:

Dense infestations can completely eliminate pasture species or displace native species in bushland.

Eradication strategies:

Because of the rapid spread of seed by birds, eradication must be done on a wide scale basis or where infestations are isolated (at least 5 Km from the closest infestation). Make a mixture of 10 grams of chlorsulfuron(750g/kg) plus 100 mL of 2,4-D ester (800g/L) plus 250 mL Pulse® Penetrant per 100 L of water. Spray plants until just wet in late winter just before the main flowering and before the flowers start to wither. Repeat annually.
Prevent seed set by picking or slashing flowers that escaped earlier treatments or applying chlorsulfuron before flowers (spathes) wither and berries start to expand (and preferably before anthesis). Repeat for 3 years. Mark infested areas at the first spraying so they can be retreated in subsequent years. Otherwise it is often very difficult to find these areas in subsequent seasons when only small, non flowering plants are present.
In restricted spraying areas the 2,4-D can be left out of the mix. Alternatively, use 1 g metsulfuron(600g/kg) plus 25 mL Pulse® per 10 L water as above.
In sensitive areas a blanket wiper may be used to apply these products. In scattered infestations, that will be spot sprayed, a mix of 50 mL Reglone® or Spray.Seed® plus 25 mL wetting agent in 10 L water provides good control and knock down within a few days, so that missed plants can be easily seen. Wear protective clothing when using this mix.
Glyphosate is relatively ineffective.
Mechanical removal is only effective if all the root fragments are removed. Multiple rotary hoeing over a few years provides control.
Cut flowers to prevent birds spreading seed.

Herbicide resistance:

None reported.

Biological Control:

Rhizoctonia (root rot), Erwinia (soft rot), spider mites (Brevipalpus and Tetranychus), Mosaic virus and Pseudomonas causes significant damage to Arum lily overseas. (Parsons, 1992).

Related plants:

No other plants in the Zantedeschia genus are naturalised in Australia.
"Green Goddess" is an ornamental species that is expected to naturalise.
Water Lettuce, another noxious weed is in the same family.

Plants of similar appearance:

The flower is very distinctive so few plants are confused with Arum Lily.
Cunjevoi (Alocasia brisbanensis)
Italian Arum or Aaron's Rod (Arum italicum)
Easter lilies (Lilium longiflorum)
Ornamental Zantedeschia species are also grown in Australia.
Taro (Colocasia esculenta) and Philodendron are in the same family.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P20. Photo.

Black, J.M. (1978). Flora of South Australia. (Government Printer, Adelaide, South Australia). P304. Diagram.

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P166-167. Photos.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P92. Photo.

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1294.1.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P734.

Moore, J.H. (1983). Experimental Summaries, Plant Research Division, Department of Agriculture of Western Australia.

Moore, J.H. and Wheeler, J.R. (2002). Southern Weeds and their Control. Photos.

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P36.

Panetta, F.D. (1988). Studies on the seed biology of arum lily (Zantedeschia aethiopica (L.) Spreng.). Plant Protection Quarterly 3(4):169-171.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P41-43. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.