Weeds of Australia - Fact Sheet

Top Scientific Name Synonyms Family Common Names Origin Naturalised Distribution Habitat Habit Distinguishing Features Stems and Leaves Flowers and Fruit Reproduction and Dispersal Environmental Impact Legislation Management Similar Species

Scientific Name

Mimosa diplotricha C. Wright ex Sauvalle var. diplotricha

Synonyms

Mimosa invisa Mart. ex Colla
Mimosa invisa Mart. ex Colla forma inermis Adelb.
Mimosa invisa Mart. ex Colla var. inermis (Adelb.) Verdc.

Family

Fabaceae: sub-family Mimosoideae (New South Wales)
Leguminosae (South Australia)
Mimosaceae (Queensland, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)

Common Names

creeping sensitive plant, giant sensitive plant, nila grass, tropical blackberry

Origin

This species is native to Mexico, Central America (i.e. Costa Rica, El Salvador, Guatemala, Honduras and Panama), the Caribbean (i.e. Cuba, Haiti, Jamaica and Puerto Rico) and tropical South America (i.e. French Guiana, Guyana, Venezuela, Brazil, Bolivia, Colombia, Ecuador, Peru and Paraguay).

Naturalised Distribution

Giant sensitive weed (Mimosa diplotricha var. diplotricha) is currently mostly confined to the coastal regions of northern Queensland, but is also present in central Queensland and on Christmas Island.

Also naturalised in tropical Africa (i.e. Burundi, Cameroon, Ethiopia, Ghana, Mozambique, Nigeria, Rwanda, Tanzania, Togo, Zaire and Zimbabwe), southern Asia (i.e. India, Sri Lanka, Laos, Cambodia, Malaysia, Taiwan, Thailand and Vietnam) and Oceania (i.e. American Samoa, Western Samoa, Cook Islands, Fiji, French Polynesia, Guam, New Caledonia, Niue, Palau, the Solomon Islands and Papua New Guinea).

Habitat

This species is mainly found in wetter habitats in tropical and sub-tropical regions. It is usually a weed of roadsides, waste areas, disturbed sites, waterways, pastures and plantation crops (e.g. sugarcane).

Habit

This species may exhibit several different growth forms and can develop into very dense thickets. It varies from being a relatively short-lived (i.e. annual, biennial or perennial) shrub with upright (i.e. erect or ascending) stems (2-3 m tall) to a climbing plant with creeping (i.e. prostrate) or scrambling stems (occasionally reaching up to 6 m long).

Distinguishing Features

• a short-lived or long-lived shrub or a climbing plant that can be upright, creeping or scrambling in habit.
  
  
• its stems are angled and armed with numerous small backwards-curved prickles (3-6 mm long).
  
  
• its twice-compound leaves have prickly stalks and consist of 4-9 pairs of branchlets, each bearing 12-30 pairs of small leaflets.
  
  
• these leaves fold together when touched (hence the name 'sensitive plant').
  
  
• its pink or purplish flowers are arranged in fluffy globular clusters (about 12 mm across).
  
  
• its flattened pods have small prickles on their edges and break up into several (usually 3-5) one-seeded segments when mature.

Stems and Leaves

The stems become somewhat woody with age and are much-branched from the base of the plant. They are strongly four or five-angled and armed with numerous small backwards-curved (i.e. recurved) prickles (3-6 mm long).

The bright green leaves (10-20 cm long) are twice-compound (i.e. bipinnate) and alternately arranged along the stems. They are borne on prickly stalks (i.e. petioles) and consist of 4-9 pairs of branchlets (i.e. pinnae). Each branchlet (i.e. pinna) bears 12-30 pairs of small leaflets (i.e. pinnules). These leaflets (6-12 mm long and about 1.5 mm wide) are stalkless (i.e. sessile), elongated (i.e. lanceolate) in shape, and have pointed tips (i.e. acute apices). The leaves usually fold together at night and when touched, hence the name "sensitive plant".

Flowers and Fruit

Numerous small pink or purplish coloured flowers are arranged in globular (i.e. spherical) clusters (about 12 mm across). These flower clusters are borne singly or in small groups on stalks (i.e. peduncles) 3.5-16 mm long that arise from the leaf forks (i.e. axils). Individual flowers have four tiny sepals, four inconspicuous petals (1-2.5 mm long), and eight prominent pink stamens that give the flower clusters a fluffy appearance. Flowering occurs mostly during autumn.

The fruit is an elongated and flattened pod (8-35 mm long and 3-10 mm wide) containing 3-5 one-seeded segments that break apart when the fruit is mature. These fruit have small prickles on their edges and are borne in dense clusters (usually about 10 in each cluster). The seeds (2-3.6 mm long and 1.9-2.7 mm wide) are light brown in colour, glossy in appearance, and egg-shaped in outline (i.e. ovate) but flattened (i.e. compressed).

Reproduction and Dispersal

This species reproduces by seed. These seeds usually remain in the prickly fruit segments and can float on water or become attached to animals and clothing. They may also be spread by machinery or as a contaminant of soil or agricultural produce.

Environmental Impact

Giant sensitive weed (Mimosa diplotricha var. diplotricha) is regarded as an environmental weed in northern Queensland.

Legislation

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

• Northern Territory: C - not to be introduced into the Territory.
  
  
• Queensland: Class 2 - landowners must take all reasonable steps to keep land free of this species (throughout the entire state). It is also illegal to sell a declared plant or its seed in this state.
  
  
• Western Australia: P1 - trade, sale or movement into the state prevented, and P2 - to be eradicated (throughout the entire state).

Management

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

• the Biosecurity Queensland Fact Sheet on this species, which is available online at http://www.dpi.qld.gov.au.
  
  
• the Northern Territory Department of Natural Resources, Environment and The Arts Agnote on this species, which is available online at http://www.nt.gov.au/weeds.

Similar Species

Giant sensitive weed (Mimosa diplotricha var. diplotricha) is very similar to giant sensitive tree (Mimosa pigra) and common sensitive plant (Mimosa pudica), which both also produces globular pink flower clusters. These species can be distinguished by the following differences:

• giant sensitive weed (Mimosa diplotricha var. diplotricha) is an upright (i.e. erect) shrub, creeper or climbing plant that has much-branched leaves (i.e. 4-9 pairs of pinnae). It produces relatively small pods (1-3.5 cm long) that contain a few (3-5) one-seeded segments.
  
  
• giant sensitive tree (Mimosa pigra) is a large shrub with an upright (i.e. erect) growth habit that has large much-branched leaves (i.e. 6-16 pairs of pinnae). It produces relatively large pods (3-12 cm long) that contain numerous (14-26) one-seeded segments.
  
  
• common sensitive plant (Mimosa pudica ) is a smaller plant, with a more low-growing (i.e. prostrate) habit, that has few-branched leaves (i.e. 1-2 pairs of pinnae). It produces relatively small pods (1- 2.5 cm long) that contain a few (1-5) one-seeded segments.