Gomphocarpus fruticosus (L.) W. T. Aiton, Apocynaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk; score: 27 (Hawaii-Pacific Weed Risk Assessment for Gomphocarpus fruticosus)

Other Latin names:  Asclepias decipiens N. E. Br.; Asclepias flavida N. E. Br.; Asclepias fruticosa L.; Asclepias rostrata N. E. Br.; Asclepias setosus Forssk.

Common name(s): [more details]

English: narrowleaf cotton bush, swan plant

Habit:  shrub

Description:  "[Gomphocarpus fruticosus] is [a] . . . shrub, to 2m . . . . The flowers have a similar structure to Asclepias, but both petals and corona are white to cream and are produced in summer. The seed pods are inflated, thin-walled, 4-6cm long, sparsely covered in soft spines and narrowing to a point; they are borne on an S-shaped stalk." (Western Weeds, p. 86)

"Habit: An upright (i.e. erect) shrubby plant usually growing 0.5-2 m tall. It is a relatively long-lived (i.e. perennial) species and normally has a rather slender few-branched habit.
"Distinguishing Features: a small, upright, long-lived shrub usually growing 0.5-2 m tall that is rather slender and few-branched; its stems and leaves contain a poisonous milky sap; its leaves are narrow (5-12.5 cm long and 5-15 mm wide) and oppositely arranged along the stems; its flowers (12-13 mm across) are white or cream in colour with five waxy petals and a crown-like structure at its centre; its distinctive, inflated fruit (4-6 cm long and 2-3.5 cm wide) are slightly curved, covered in soft bristles, and gradually taper to a short point at their tips; these fruit contain numerous seeds topped with silky white hairs (about 30 mm long).
"Stems and Leaves: The upright (i.e. erect) stems are pale green in colour and covered in small whitish hairs (i.e. hoary) when young. These stems turn brown in colour and become somewhat woody with age. All parts of the plant, and particularly the stems, exude a white milky sap (i.e. latex) when broken or damaged. The leaves are rather narrow or elongated (i.e. linear-lanceolate) in shape and taper to a point at both ends (i.e. with attenuate bases and acute apices). These leaves (4-12.5 cm long and 5-15 mm wide) are oppositely arranged along the stems and borne on short stalks (i.e. petioles) 3-10 mm long. Their upper surfaces are usually shiny and pale green in colour while their lower surfaces are paler and duller in appearance.
"Flowers and Fruit: The flowers are borne in loose, drooping (i.e. pendulous) clusters (i.e. umbels) in the forks (i.e. axils) of the leaves. These clusters consist of 3-10 flowers, each flower being borne on a slender stalk (i.e. pedicel) 10-20 mm long, and the flower stalks (i.e. pedicels) all radiate from the same point. The flowers (about 2 cm long and 12-13 mm across) are white or cream coloured (sometimes with slightly pinkish centres) and are slightly tubular in appearance. They have five waxy petals that are used together at the base with lobes (i.e. corolla lobes) 6-7 mm long. In the centre of these flowers are five pouch-like projections that form a distinctive crown-like structure (i.e. corona). The flowers also have five small and narrow sepals and five stamens. Flowering occurs from spring through until early autumn (i.e. from August to April), but is most abundant during summer. The distinctive thin-walled fruit are balloon-like or bladdery in appearance (4-7 cm long and 1.5-3.5 cm wide) and light green in colour. Often referred to as 'pods', they are actually follicles, and are borne on an S-shaped stalk (i.e. pedicel). These fruit are narrowly egg-shaped (i.e. narrowly ovoid), slightly curved (i.e. falcate), and covered in soft spines or bristles up to 10 mm long. They gradually taper to a short pointed projection (i.e. beak) at one end, turn brown in colour with age, and split open at maturity to release their numerous seeds. These seeds (about 6 mm long and 3 mm wide) are brown or black in colour, flattened, and topped with a tuft (i.e. coma) of numerous white silky hairs (about 30 mm long). The fruit are present from late summer through to late spring (i.e. from February to December)." (Weeds of Australia [punctuation and formatting adapted by PIER])

Habitat/ecology:  "This species grows in a wide range of environments including warm temperate, sub-tropical, tropical and occasionally even semi-arid regions. It is a weed of roadsides, disturbed sites, waste areas, waterways, pastures, open woodlands and fallows." (Weeds of Australia)

In introduced areas in Australia: "It usually grows along forest margins or grassy remnant native vegetation..., but has also been reported from coastal environs. In the...inland parts of northern New South Wales, it is also listed among the top 20 priority environmental weed species. It is also a common weeds of endangered brogo wet vine forest and dry rainforest ecological communities...." (Weeds of Australia)

Propagation:  "Reproduction and Dispersal: This species reproduces by seed and suckers may also be produced off lateral roots that are closest to the soil surface. The seeds are most commonly spread by wind and water. They may also be dispersed as a contaminant of agricultural produce (e.g. fodder) or in mud attached to animals, machinery and other vehicles." (Weeds of Australia [punctuation and formatting adapted by PIER])

"Narrow-leaf cotton bush spreads by seeds, which usually germinate in spring or autumn, but can germinate at any time in warm, moist conditions. Seedlings have the ability to resprout from the crown or root if the above ground parts of the plant are damaged. The plants grow through summer and usually flower in the second year from October to April." (Western Australian Government)

Native range:  Africa: Kenya, Uganda, Djibouti, Eritrea, Ethiopia, Somalia, Sudan, Angola, Malawi, Mozambique, Zambia, Zimbabwe, Botswana, Lesotho, Namibia, South Africa, Swaziland; Arabian Peninsula: Oman, Saudi Arabia, Yemen (GRIN)

South Africa (Western Weeds, p. 86)

Impacts and invaded habitats:  "Environmental Impact: Narrow-leaved cotton bush (Gomphocarpus fruticosus) is regarded as an environmental weed in Western Australia, New South Wales, Tasmania, Victoria and Queensland. It was recently listed as a priority environmental weed in two Natural Resource Management regions. This species is currently of most concern in New South Wales and Western Australia. It is a common weed of grasslands, open woodlands and disturbed sites in these states and also invades vegetation near waterways and around other waterbodies (i.e. riparian areas). It competes with native plants in these habitats and is capable of forming dense thickets. ... This species was listed as a moderately important species in the Environmental Weed Strategy of Western Australia and has also been recorded in several conservation areas in this state.... Narrow-leaved cotton bush (Gomphocarpus fruticosus) is also present in conservation areas in New South Wales...and appears on several regional environmental weed lists.... It usually grows along forest margins or grassy remnant native vegetation..., but has also been reported from coastal environs. In the...inland parts of northern New South Wales, it is also listed among the top 20 priority environmental weed species. It is also a common weeds of endangered brogo wet vine forest and dry rainforest ecological communities.... Narrow-leaved cotton bush (Gomphocarpus fruticosus) is also listed as a common environmental weed of the Adelaide region in South Australia.
"Other Impacts: Narrow-leaved cotton bush (Gomphocarpus fruticosus) is poisonous to livestock and humans, and has caused deaths in cattle, sheep and poultry. It is seldom consumed fresh by livestock, but may be dangerous if it contaminates fodder or chaff. Severe gastroenteritis is the main symptom of poisoning by this species. Dense infestations may also reduce the productivity of pastures." (Weeds of Australia [punctuation and formatting adapted by PIER])

If you know of other invaded habitats or impacts, please let us know.

Presence:

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Asia Asia	Arabian Peninsula (southern)	native	Queensland Government (year unknown) accessed 20190205, see ref for details (countries)
Asia Asia	Asia (east)	native	Randall, R. P. (2017) (p. 1675)
Asia Asia	Asia (temperate)	native	U.S. National Plant Germplasm System (year unknown) accessed 20190124; see ref for country details
Asia Asia	Asia (western)	native	Randall, R. P. (2017) (p. 1675)
Asia Asia	Cyprus	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Asia Asia	Cyprus		Randall, R. P. (2017) (p. 1675)
Asia Asia	Israel		Randall, R. P. (2017) (p. 1675)
Australia Australia	Australia	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Australia Australia	Australia	invasive cultivated	Randall, R. P. (2017) (p. 1675)
Australia Australia	Australia		Randall, R. P. (2017) (p. 1676)
Australia Australia	Australia	invasive	Randall, R. P. (2017) (p. 467)
Australia Australia	Australia	introduced	Queensland Government (year unknown) accessed 20190205, see ref for details (states)
Australia Australia	Tasmania	introduced	Queensland Government (year unknown) accessed 20190205
Japan Japan	Japan		Randall, R. P. (2017) (p. 1675)
Japan Japan	Japan		Randall, R. P. (2017) (p. 467)
New Zealand New Zealand	New Zealand (country)	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
New Zealand New Zealand	New Zealand (country)	invasive	Randall, R. P. (2017) (p. 1675)
New Zealand New Zealand	New Zealand (country)	introduced	Queensland Government (year unknown) accessed 20190205 "naturalised"
South America (Pacific rim) South America (Pacific rim)	Colombia		Randall, R. P. (2017) (p. 1675)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124; "naturalized"
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)		Randall, R. P. (2017) (p. 467)
United States (west coast) United States (west coast states)	USA (California)	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124; "adventive"

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island		Randall, R. P. (2017) (p. 1675)
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island	introduced	Queensland Government (year unknown) accessed 20190205 "naturalised"
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Africa Africa	Africa	both native and introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124; see ref for country details
Africa Africa	Africa	native	Randall, R. P. (2017) (p. 1675)
Africa Africa	Africa	native	Randall, R. P. (2017) (p. 467)
Africa Africa	Africa (eastern)	native	Queensland Government (year unknown) accessed 20190205, see ref for details (countries)
Africa Africa	Africa (southern)	native	Queensland Government (year unknown) accessed 20190205, see ref for details (countries)
Africa Africa	Azores	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Africa Africa	Azores		Randall, R. P. (2017) (p. 1675)
Africa Africa	Azores	introduced	Queensland Government (year unknown) accessed 20190205 "naturalised"
Africa Africa	Botswana		Randall, R. P. (2017) (p. 467)
Africa Africa	Ethiopia		Randall, R. P. (2017) (p. 1675)
Africa Africa	Madagascar		Randall, R. P. (2017) (p. 1675)
Africa Africa	Madeira Islands	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Canary Islands Canary Islands	Canary Islands	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Canary Islands Canary Islands	Canary Islands		Randall, R. P. (2017) (p. 1675)
Eurasia Eurasia	Georgia		Randall, R. P. (2017) (p. 1675)
Eurasia Eurasia	Turkey	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Eurasia Eurasia	Turkey		Randall, R. P. (2017) (p. 1675)
Europe Europe	Albania		Randall, R. P. (2017) (p. 1675)
Europe Europe	Austria		Randall, R. P. (2017) (p. 1675)
Europe Europe	Crete		Randall, R. P. (2017) (p. 467)
Europe Europe	Croatia		Randall, R. P. (2017) (p. 1675)
Europe Europe	Europe	invasive	Randall, R. P. (2017) (p. 1675)
Europe Europe	Europe (southern)	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
Europe Europe	France	invasive	Randall, R. P. (2017) (p. 1675)
Europe Europe	Greece		Randall, R. P. (2017) (p. 1675)
Europe Europe	Greece	invasive	Randall, R. P. (2017) (p. 467)
Europe Europe	Italy		Randall, R. P. (2017) (p. 1675)
Europe Europe	Italy	invasive	Randall, R. P. (2017) (p. 467)
Europe Europe	Mediterranean region	invasive	Randall, R. P. (2017) (p. 1675)
Europe Europe	Portugal	invasive	Randall, R. P. (2017) (p. 1675)
Europe Europe	Sardinia	invasive	Randall, R. P. (2017) (p. 1675)
Europe Europe	Sardinia	invasive	Randall, R. P. (2017) (p. 467)
Europe Europe	Spain	invasive	Randall, R. P. (2017) (p. 1675)
India India	India (Republic of)	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124
India India	India (Republic of)		Randall, R. P. (2017) (p. 1675)
India India	India (Republic of)	introduced	Queensland Government (year unknown) accessed 20190205 "naturalised"
Northern Atlantic Region Northern Atlantic Region	Macaronesia	invasive	Randall, R. P. (2017) (p. 1675)
South Africa South Africa	South Africa (Republic of)		Randall, R. P. (2017) (p. 1675)
South Africa South Africa	South Africa (Republic of)	invasive	Randall, R. P. (2017) (p. 467)
South America South America	Argentina		Randall, R. P. (2017) (p. 467)
United States of America United States	United States		Randall, R. P. (2017) (p. 467)
Venezuela Venezuela	Venezuela (Bolivarian Republic of)	introduced	U.S. National Plant Germplasm System (year unknown) accessed 20190124; "naturalized"
World World	Worldwide	cultivated	Randall, R. P. (2017) (p. 1675)
World World	Worldwide		Randall, R. P. (2017) (p. 1676)
World World	Worldwide		Randall, R. P. (2017) (p. 467)

Comments:  "[Gomphocarpus fruticosus] is capable of forming dense thickets." (Western Weeds, p. 86)

present on Raoul Island (Kermadec Group) (Turning the Tide, p. 370)

cultivated; adventive in California (USA); naturalized in Africa (Portugal [Azores, Madeira Islands], Spain [Canary Islands], Sudan, Morocco, Cote D'Ivoire, Guinea, Senegal, Cameroon, Madagascar, Mauritius, Reunion), Asia (Cyprus, Turkey, India), Australia, New Zealand, Europe (Albania, Croatia, Greece, Italy, France, Portugal, Spain), South America (Venezuela, Peru) (GRIN)

Control:  "What you can do about narrow-leaf cotton bush: Practice good biosecurity to avoid introducing narrow-leaf cotton bush or other weeds and pests to your property. Do not cultivate narrow-leaf cotton bush as a garden plant and avoid purchasing soil or other landscaping supplies that could be contaminated with weed seeds or bulbs. Take particular care when purchasing fodder - cheap hay is not a bargain if it is full of weed seeds or toxic plants. Ensure contractors entering your property have clean equipment to avoid the introduction of new weeds – install a washdown bay if necessary. If you have narrow leaf cotton bush on your property, take care to prevent it spreading to other properties. Control small infestations before they spread. Join forces with your neighbours and local government authority to remove narrow-leaf cotton bush and other weeds. Narrow-leaf cotton bush has a shallow root system so small infestations can be dealt with by hand pulling - make sure you get all the roots to prevent suckering. Take appropriate measures to avoid contact with the toxic sap, such as wearing rubber gloves and overalls, and washing hands thoroughly before eating. Contact with the sap could cause a rash or other symptoms for which medical advice should be sought.
"Destroy any seeds in a way to avoid spreading the plant. Larger infestations are best dealt with by a combination of spraying, slashing, burning and pasture management. Burning heavy infestations of cotton bush is an effective, low cost option which damages seed on and near the soil surface. The reduction in the soil seed bank allows increased pasture production. Ploughed firebreaks can provide an ideal seedbed for narrow-leaf cotton bush and other weeds, so chemical firebreaks may be better. Chemical firebreaks have the added advantage of providing a firm surface that can be used as an access track or an escape route in the event of fire.
"Control options: Seedlings, plants less than 1m tall: Minor infestations or small patches of young seedling plants can be sprayed with glyphosate or physically removed by grubbing or hand pulling. At this growth stage they are unlikely to have seeded and can be disposed of by drying and burning. Larger infestations are effectively controlled using glyphosate to ensure all seedlings are controlled before they mature and produce seed. Mature plants more than 1m tall: Small areas can be sprayed or physically removed by grubbing or pulling. Plants that have been removed will dry out quickly and should be burnt or deep buried. Mature plants with seed pods attached have the potential to spread seed and infest new areas when moved away from their original location and should be disposed of as close to the infestation as possible. Large infestations of mature plants can be managed and controlled using various techniques including slashing, burning and spraying. All methods reduce the potential for plants to produce seed. Slashing and burning must be followed up with herbicide treatment to control regrowth and seedlings. Spraying with glyphosate mixed with metsulfuron methyl is very effective in controlling larger cotton bush plants and is best applied by a high volume hand lead sprayer. Plants should be sprayed until the leaves are wet, almost to the point that liquid is running off. The table below provides the amount of glyphosate herbicide per 10L knapsack or 100L tank mix for products that contain 360, 450 or 540g/L or 680g/kg of glyphosate. Other herbicides used for the control of narrow-leaf cotton bush include triclopyr and metsulfuron methyl. In bushland areas, wipe the leaves with a mixture of 1L glyphosate plus 2L water before flowering when the plants are actively growing in spring to early summer. The larvae of the wanderer butterfly occasionally cause stem and leaf damage to cotton bush, however it is not sufficient to kill infestations of the plant." (See also detailed pesticide application information in the tables ["Summary of control options for narrow leaf cotton bush..."] included in the cited document.) (Western Australian Government [punctuation and formatting adapted by PIER])

If you know of other control methods for Gomphocarpus fruticosus, please let us know.