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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
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Click on images to enlarge

terrestrial infestation (Photo: Land Protection, QDNRW)

aquatic infestation (Photo: Land Protection, QDNRW)

terrestrial habit (Photo: Land Protection, QDNRW)

aquatic habit (Photo: Land Protection, QDNRW)

aquatic habit (Photo: Land Protection, QDNRW)

prickly stem and twice-compound leaf (Photo: Land Protection, QDNRW)

close-up of flowers and flower buds (Photo: Land Protection, QDNRW)

close-up of globular flower cluster (Photo: Land Protection, QDNRW)

immature and mature fruit (Photo: Land Protection, QDNRW)

Mimosa pigra

Scientific Name

Mimosa pigra L.

Synonyms

Mimosa asperata L.
Mimosa asperata L. var. pigra Willd.
Mimosa berlandieri A. Gray ex Torr.
Mimosa brasiliensis Niederl.
Mimosa canescens Willd.
Mimosa ciliata Willd.
Mimosa hispida Willd.
Mimosa invisa Mart.
Mimosa pellita Humb. & Bonpl. ex Willd.

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

bashful bush, bashfulplant, black mimosa, catclaw mimosa, giant mimosa, giant sensitive plant, giant sensitive tree, mimosa, sensitive plant, sensitive tree, thorny sensitive plant, thorny sensitiveplant

Origin

Native to Mexico, Central America (i.e. Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panama), the Caribbean and tropical South America (i.e. French Guiana, Guyana, Surinam, Venezuela, Brazil, Colombia, Ecuador, Peru and northern Argentina). Possibly also native to large parts of Africa, Madagascar and Mauritius (or an early introduction to these places).

Naturalised Distribution

At present the distribution of this species is mostly limited to the northern parts of the Northern Territory. It has also been recorded more recently from the coastal areas of central Queensland (i.e. at Peter Faust Dam near Proserpine).

Also naturalised in tropical Asia (i.e. Cambodia, Malaysia, Singapore, Thailand and Vietnam), south-eastern USA (i.e. Florida), the Galapagos Islands and Hawaii.

Habitat

A weed of roadsides, waterways, drainage ditches, floodplains, swamps, seasonally flooded wetlands, lowland pastures and the edges of water bodies in wetter tropical and sub-tropical regions.

Habit

An upright (i.e. erect), much-branched, prickly shrub growing 3-6 m tall and forming dense thickets.

Distinguishing Features

Stems and Leaves

Young stems are greenish in colour, rounded (i.e. terete), have scattered prickles (5-12 mm long), and are covered with short stiff hairs. Older stems become woody and turn greyish in colour.

The twice-compound (i.e. bipinnate) leaves are alternately arranged along the stems and borne on stalks (i.e. petioles). These leaves (20-31 cm long) often have small prickles present along their main axis (i.e. petiole and rachis). They consist of several (6-16) pairs of branchlets (i.e. pinnae), each about 5 cm long and bearing numerous (20-45) pairs of small leaflets (i.e. pinnules). The leaflets (3-12 mm long and 0.5-2 mm wide) are elongated (i.e. lanceolate) in shape and stalkless (i.e. sessile). They fold together when touched and also during the night.

Flowers and Fruit

The flowers are pale pink or mauve in colour and arranged in fluffy, globular clusters (10-20 mm across). One to three (usually two) of these small flower clusters are produced on stalks (i.e. peduncles) 2-7 cm long, emanating from each upper leaf fork (i.e. axil). Individual flowers have four tiny sepals (0.75-1 mm long), four inconspicuous petals (2-3 mm long), and eight prominent pinkish stamens that give the flower clusters their fluffy appearance. Flowering occurs mostly during summer and early autumn.

The fruit is an elongated and flattened pod (30-120 mm long and 7-14 mm wide) that is covered in bristly hairs. The pods are borne in clusters (of 1-30), are straight or slightly curved, and are initially green in colour. As they mature they turn brown, and when fully mature they break up into about twenty (14-26) one-seeded segments. The seeds (4-6 mm long and 2-2.5 mm wide) are light brown, brown or greenish-brown in colour, elongated (i.e. oblong) in shape, and somewhat flattened (i.e. compressed).

Reproduction and Dispersal

This plant reproduces by seed and also vegetatively via adventitious roots and suckers from cut stems.

The seeds survive being eaten by animals and are often spread in this manner. The one-seeded segments also readily become attached to animals, vehicles and clothing and can be dispersed in water and mud.

Environmental Impact

Giant sensitive tree (Mimosa pigra) is regarded as a significant environmental weed in the Northern Territory, and as a potentially significant environmental weed in Queensland and Western Australia. This species is one of the 20 Weeds of National Significance (WoNS) in Australia, largely due to its impact on natural ecosystems, and is actively weed managed by community groups in the Northern Territory.

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

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