Swan plant

Gomphocarpus fruticosus (L.) W.T.Aiton

Synonyms - Asclepias arborescens, Asclepias fruticosa.

Family: - Asclepiadaceae.


Asclepias is named after Asklepios a god of medicine because a related plant was supposed to be an antidote for poison.

Fruticosa is from the Latin word meaning "thick with leaves" describing the plants bushy appearance.

Swan plant - because the fruit looks like a swan.

Other Names:

Arghel (Syria)

Balloon Cotton - Refers to the balloon like fruit and cottony hairs on the seed.

Cape Cotton - refers to its origin around the Cape of Good Hope inn South Africa and the cottony hairs on the seed.

Cotton Bush - refers to the to the cottony hairs on the seed.

Duck Bush - refers to the duck like shape of the fruit.

Duck bushes

Milkweed (USA) - refers to the copious milky sap that is exuded when the plant is cut.

Narrowleaf Cotton bush - refers to the narrower leaves on this species than the very similar A. physocarpa

Wild Cotton

Wildekapok (S. Africa)


Cream to white flowers occur in summer and produce a bladdery, soft spined, 4-6 cm long fruit on a S shaped stalk.

Swan plant or Cotton Bush (Gomphocarpus fruticosus) is an erect shrub to 2 m high producing a milky sap from all parts when damaged. The narrow leaves are opposite, 40-135 mm long, sparsely hairy and pointed. The flowers are white to cream and arranged in small, often pendulous clusters in the leaf axils. Each flower is 12-13 mm across, with 5 spreading to reflexed petals and a central crown of 5 pouch-like lobes. The inflated green fruit is egg-shaped, 45-60 mm long, and held on an S-shaped stalk. The fruit surface is covered with soft slender spines which are up to 15 mm long. The roots are aromatic and form suckers when damaged.

Swan plant is native to South Africa and was introduced as a garden plant for its attractive fruits, but has become a weed of roadsides, drainage lines, pasture and disturbed areas, sometimes invading undisturbed bushland. It is a declared weed of WA, flowering from November to February.





Opposite pairs. Each pair at right angles to the pair below. Dull green, occasionally with a shiny upper surface.

Stipules - Small.

Petiole - 1-13mm long.

Blade - Narrowly oval. 50-125 x 6-20 mm. Tip tapered to a point. Smooth edges or slightly toothed. Surface with short, fine hairs. Midrib indented on the top surface and on the lower surface it is protruding and a lighter colour.

Sheath -

Stem leaves -


Slender, erect, branched, 600-2000 mm tall. Pale green or downy white, hairy, becoming hairless with age. Woody centre, softer outside. May be hollow. Copious milky sap. Coppice if damaged.

Flower head:

Loose drooping or erect umbel on a 20-50 mm hairy stalk in upper leaf axils. Hairs short and pale. 3-10 flowered.


On hairy 10-15 mm slender stalks. Hairs short and pale. Stalk with a small bract at the base. Shortly tubular. Waxy.

Bracts -

Ovary - style tip 5 angled. Slender style.

Sepals - narrowly oval. 2mm long. Short pale hairs. Free with 2 glands between each one.

Petals - red or pink or white. 6mm long, joined at the base. Bend back at maturity, with a yellow, erect, 5 lobed crown about 6mm long inside. Lobes pouch-like or hollow with 2 incurved teeth.

Stamens - joined at the base.

Anthers - with wings.


Oval, bladdery, beaked pods (follicle) with soft slender bristles to 10 mm long on an 'S' shaped stalk. Lime green. With many tightly packed seeds in a thin walled sac. Air space between the outer wall and the seeds. 50-60 mm long. 20-25 mm wide. Splits to reveal long white feathery hairs attached to the seed.


Flattened. Narrow wings. Brown. Egg shaped. 5-6mm long by 2-3mm wide. Tuft of white silky hairs about 30mm long at top of seed.


Aromatic. Solid crown. Slender taproot. Several laterals. Sucker if damaged.

Key Characters:


Life cycle:

Perennial. Seeds germinate from spring to autumn, with a peak in late spring and early autumn. They develop rapidly and within a few weeks have produced roots and crowns capable of re-sprouting if damaged. It is semi-dormant in winter. Plants don't normally flower in their first season and older plants flower from October to April.



By seed and suckers.

Flowering times:

November to February in Perth.

October to April in Tasmania.

Seed Biology and Germination:

Produces large quantities of seed that germinates readily over a wide range of conditions.

Seed remains viable in the soil for a long time.

Vegetative Propagules:

Suckers from roots.



It produces soil toxins that reduce the germination of other plants.

Population Dynamics and Dispersal:

Mainly spread by seed assisted by wind and water.

Seed is spread as a contaminant of agricultural produce.

Plants transported for home gardens assisted the initial spread. The attractive swan like fruits are collected and distributed by children.

Suckering increases the density of stands and increases it area along the edges.

Acrid milky sap protects them from grazing.

Origin and History:

South Africa, Ethiopia, Mediterranean.

Introduced as garden species or for the making of hats before 1802 in Sydney. It was first described as an invasive pest plant in 1817. By 1894 it was present in all mainland states and causing concern in WA where it was spreading rapidly near Dardanup and Burekup.





Humid tropics and sub-tropics.

Moderate rainfall areas.


Thrives in areas of low fertility and on good soils, especially if it is burnt.

Plant Associations:

Cleared rain forest.




Tested as a kapok substitute but abandoned because of fibre brittleness and harvesting difficulties.


A weed of roadsides, disturbed areas, pastures, native bush and watercourses.

Forms dense patches reducing grazing areas. It is one of the few plants that will invade undisturbed bush.


Toxic to sheep, cattle and pigs, but unpalatable, so it doesn't usually cause problems. It has caused poultry deaths when chaffed in green feed. Cases of poisoning have been due to accidental grazing of young seedlings.

Toxic to rabbits and guinea pigs.

Toxicity probably due to cardiac glycosides and resinoids.


Gastro enteritis and congestion of the gut.


Remove stock from areas that have seedlings.


Noxious weed of WA.

Management and Control:

Local spread is by suckering and seed. Major spread is by wind and water transporting the winged tufted seed or the bladdery fruits floating in streams. Seed may contaminate produce or be transported in mud attached to animals and machines. Mechanical removal is effective if most of the root system is also removed. Repeated cultivation provides some control. Mowing or slashing in winter is effective if seedlings are sprayed or slashed as required. Seedlings can be controlled with dicamba and older plants with glyphosate or triclopyr applied in spring to early summer when they are actively growing. The larva of the Lesser Wanderer Butterfly occasionally causes significant damage to cotton bush.


Eradication strategies:

Mechanical removal is effective if most of the root system is removed. Repeated cultivation provides some control. If possible, cultivate in autumn to encourage seed germination and lift crowns from the soil. Mowing or slashing in winter is effective if seedlings are also sprayed or slashed as necessary.

Seedlings can be controlled with 4 L/ha glyphosate(450g/L) or Grazon® applied in spring to early summer when the Swan Plant is actively growing.

For mature plants, spray foliage and a 1 metre buffer area until just wet, with 100 mL Grazon plus 25 mL Pulse® in 10 L of water before flowering when the plants are actively growing in spring to early summer. This will control the parent plant and help control suckering and subsequent germinations.

In bushland areas, wipe the leaves with a mixture of 1 L glyphosate plus 2 L water before flowering when the plants are actively growing in spring to early summer .

The larva of the Lesser Wanderer Butterfly occasionally causes significant damage to cotton bush.

Herbicide resistance:

Relatively tolerant to the hormone herbicides.

Biological Control:

The larvae of the Wanderer Butterfly (Danaus plexippus and Danaus chrysippus) are often associated with the plant and can cause significant damage. These insects are not native to Australia.

Related plants:

Balloon Cotton Bush (Gomphocarpus physocarpus) is very similar but has broader leaves and fruit that is on a straight stalk and is more globular and doesn't taper into the short curved beak characteristic of Swan Plant.

Broad leaved Cotton bush (Asclepias rotundifolia)

Redhead Cotton bush (Asclepias curassavica) is also similar but has larger red flowers with a yellow central crown and a narrow fruit which lacks spiny outgrowths.

Plants of similar appearance:


A.P.B. Advisory leaflet No. 52 (1979)9

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P699. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P554. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P97-99.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P153-155. Diagram.

Goyder, David - Has a good key of African species.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne). p???.

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #136.2.

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). P525.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). p179-182.

Meadly (1971) J of Ag. 12:65-8.


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