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Scientific Name
Synonyms
Family
Common Names
Origin
Cultivation
Naturalised Distribution
Habitat
Habit
Distinguishing Features
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Environmental Impact
Other Impacts
Legislation
Management
Similar Species
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Click on images to enlarge

infestation (Photo: Land Protection, QDNRW)

habit (Photo: Forest and Kim Starr, USGS)

habit (Photo: Forest and Kim Starr, USGS)

leaves and flower clusters (Photo: Land Protection, QDNRW)

young leaves (Photo: Sheldon Navie)

leaf undersides and flower clusters (Photo: Forest and Kim Starr, USGS)

flowers and flower buds (Photo: Forest and Kim Starr, USGS)

close-up of flower (Photo: Forest and Kim Starr, USGS)

immature fruit (Photo: Forest and Kim Starr, USGS)

close-up of immature fruit (Photo: Land Protection, QDNRW)

mature fruit with seeds (Photo: Forest and Kim Starr, USGS)

close-up of seeds with hairs removed (Photo: Steve Hurst at USDA PLANTS Database)

Calotropis procera

Scientific Name

Calotropis procera (Ait.) Ait.

Synonyms

Asclepias procera Ait.
Calotropis procera (L.) Dryand.
Calotropis procera (Willd.) R. Br.

Family

Asclepiadaceae (the ACT, Victoria, Tasmania, South Australia, Western Australia and the Northern Territory)
Apocynaceae (Queensland and New South Wales)

Common Names

apple of Sodom, auricula tree, cabbage tree, calotrope, calotropis, Dead Sea apple, giant milkweed, Indian milkweed, kapok tree, King Edward's crown, king's crown, king's crown kapok, Prince of Wales' crown, rubber bush, rubber plant, rubber tree, rubberbush, small crown flower, small crownflower, Sodom apple, Sodom's milkweed, swallowwort

Origin

Native to northern Africa (i.e. Algeria, Egypt, Libya, Morocco, Eritrea, Ethiopia, Somalia, Sudan, Kenya, Tanzania, Uganda, Cameroon, Equatorial Guinea, Gambia, Ghana, Guinea-Bissau, Mauritania, Nigeria, Senegal and Sierra Leone), the Arabian Peninsula (i.e. Saudi Arabia, Oman and Yemen), the Middle East, and southern Asia (i.e. Afghanistan, Pakistan, Nepal, India, Myanmar, Thailand and Vietnam).

Cultivation

This species was cultivated as a garden plant (i.e. ornamental) in the past, but it is now out of favour because it is poisonous and generally regarded as a weed.

Naturalised Distribution

This species is widespread in the drier northern parts of Australia. It is mostly found in northern Queensland, north-western Western Australia and in the northern parts of the Northern Territory. Also present in other parts of the Northern Territory, and recorded in South Australia and New South Wales.

It has also become naturalised in parts of Central America, northern South America, the Caribbean, south-western USA (i.e. California) and in Hawaii.

Habitat

Found mostly in semi-arid and arid inland areas, as well as in the drier parts of tropical and sub-tropical regions. A weed of disturbed sites, roadsides, waste areas, near inland watercourses, coastal sand dunes, grasslands, open woodlands and pastures.

Habit

An upright (i.e. erect) shrub or small tree usually growing 1-4 m tall.

Distinguishing Features

Stems and Leaves

The stems and leaves have a waxy appearance and contain a milky white sap (i.e. latex). Branching occurs from the base of the plant upwards. Younger stems are greyish-green in colour, smooth in texture, and have a covering of whitish coloured hairs (i.e. they are hoary). Mature stems have a deeply fissured, cork-like, bark that is light brown in colour.

The large, relatively thick, leaves (5-30 cm long and 4-15 cm wide) are also greyish-green in colour and have entire margins. They are oppositely arranged and have stem-clasping bases (i.e. they are sessile) or very short stalks (i.e. petioles) 3-4 mm long. These leaves are rounded (i.e. orbicular) or egg-shaped in outline (i.e. ovate) with shortly-pointed tips (i.e. acute apices). Their upper surfaces are mostly hairless (i.e. glabrous), while their undersides may be densely covered in tiny white hairs or have a tuft of stiff hairs at the base of the central vein (i.e. midrib).

Flowers and Fruit

The flowers (15-25 mm across) are borne in clusters, each containing 3-15 flowers, in the forks of the uppermost leaves (i.e. in axillary inflorescences). The main stalk of these flower clusters (i.e. peduncle) is 20-55 mm long and each flower has a stalk (i.e. pedicel) about 15-25 mm long. These flowers have five spreading petals (7-10 mm long and 6-10 mm wide) that are white or pinkish in colour, with much darker purple or purplish-brown tips, and a crown-like centre (i.e. corona) that is also purplish in colour. They also have five sepals (about 5 mm long and 3 mm wide) that are oval (i.e. elliptic) or egg-shaped in outline (i.e. ovate) and five stamens. Flowering occurs mostly during winter.

The fruit is a large (6-12 cm long and 3-7 cm wide) bladdery 'pod' (i.e. follicle) that is greyish-green in colour and rounded (i.e. sub-globose) to somewhat egg-shaped (i.e. obliquely ovoid). These fruit have thick and spongy skins which split open at maturity. Each fruit contains numerous brown, flattened seeds (about 6 mm long and 4 mm wide) that are topped with a tuft (i.e. coma) of long, white, silky hairs (35-50 mm long).

Reproduction and Dispersal

This plant reproduces mainly by seeds, though local increase in the size and density of populations also occurs via suckering from the roots.

The seeds can be spread long distances by wind and water and can also be dispersed in mud that becomes attached to animals and vehicles.

Environmental Impact

Calotrope (Calotropis procera) is regarded as an environmental weed in the Northern Territory, Western Australia and Queensland. It thrives on poor soils, particularly where overgrazing has removed competition from native grasses, and forms dense thickets which compete with native plant species and transform the appearance of savanna plant communities. This species is culrrently listed as a priority environmental weed in three Natural Resource Management Regions and it is being actively managed by community groups in the Northern Territory.

Other Impacts

The milky sap is toxic to humans and sometimes also to livestock. It can also hinder pastoralism by reducing the productivity of rangeland pastures and making mustering more difficult.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Similar Species

Calotrope (Calotropis procera) is very similar to giant calotrope (Calotropis gigantea). These two species can be distinguished by the following differences: