Common Name:

General Information

Mimosa pigra is a stout, stiff, prickly shrub. The stems are branched, 1 - 6 metres long, with dense growth[]. The plant is usually erect[], but sometimes has a more creeping habit[].
The plant is gathered from the wild for local medicinal use, and has been cultivated to counter soil erosion and provide material for green manures.

Known Hazards

None known

Botanical References

Range

S. America from Argentina north through Central America to Mexico, the Caribbean. Tropical Africa.

Habitat

Moist, open sites, forming a monospecific stand and competing with sedgeland and grassland communities so that the ground flora under dense stands is sparse to non-existent. Its favoured habitat is around water and on floodplains[]

Properties

Weed Potential	Yes
Medicinal Rating
Other Uses Rating
Habit	Shrub
Height	4.00 m
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

The plant grows in areas of the lowland tropics where there is a distinct dry season[]. It is usually found at elevations from near sea level to 700 metres, occasionally to 1,000 metres[, ]. It grows best in areas where annual daytime temperatures are within the range 15 - 30°c, but can tolerate 8 - 38°c[]. When dormant, the plant can survive temperatures down to about °c, but young growth is more tender and can be severely damaged at °c[]. It prefers a mean annual rainfall in the range 800 - 1,500mm, but tolerates 500 - 2,00mm[].
Requires a sunny position[]. Found most commonly in the wild in soils ranging from black cracking clays to sandy clays to coarse siliceous river sand[]. Prefers a pH in the range 5.5 - 7, tolerating 5 - 7.5[]. Plants are tolerant of drought, and also of seasonal inundation of the soil[].
In its native range, the plant is kept in check by insect and fungal pathogens. However, these natural controls are absent in other countries and, after it was introduced to the Australian Darwin Botanic Gardens in the late 1800s it escaped into the wild[]. Since the late 1970's, this plant has become a serious weed of pastureland and national parks in northern Australia[]. It has several characteristics that enable it to do well in open disturbed sites: it grows quickly, it can withstand drought and floods, and the seeds float. It threatens biological diversity by replacing wetlands with an impenetrable thorny thicket. It is also detrimental to pastoralism, tourism and traditional use of land by Aboriginal people[]. The plant presents a very different picture in its native range, where its natural habitat is mainly marginal areas of canals, rivers and lakes, and this gives some hope to researchers looking for biological controls[]. In Mexico, for example, it is a rather obscure weed[]. It would probably not be a major weed problem in regions with an annual rainfall of less than 750 mm or greater than 2,250 mm, except in cases of clear cutting[]. Seeds of this prickly shrub spread through river systems by floating downstream[]. They are also carried between river systems by animals, or in mud on vehicles[].
Mature plants are resistant to fire, the majority of plants regrowing from the base of stems[]. Young plants are more susceptible, but a large proportion also regrow[].
Mimosa infestations can expand very rapidly, so it is important to prevent the spread to new areas, as well as to control existing infestations[]. Current control methods are costly and require lengthy ongoing commitment[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

None known

Medicinal

The plant is used in tropical Africa as a tonic and a treatment for diarrhoea, gonorrhoea and blood poisoning[].

The leaf is said to contain mimosine; it is purgative and perhaps tonic[]. A decoction of the leaves and stems is used to treat thrush in babies and bed-wetting in children[]. The powdered leaf is taken with water to relieve swelling[].
The leaves are macerated in the hands and rubbed on the eyes of babies or children to put them to sleep when they are irritable[].

The root is apparently aphrodisiac to some persons and calming to others[].
The root ash is sprinkled over leprous patches on the skin[].

The seed is emetic and expectorant[]. It is used for treating tooth troubles[].

Agroforestry Uses:

The plant can be used on the steep banks of water reservoirs as an erosion-control measure[]. When grown at the damp water-inlet areas in reservoirs, it can remove debris from floodwater entering the reservoir[].
It has been used as a green manure and cover crop in Thailand since the 1960s[].
The plant is a good source of pollen for bees[].

Other Uses

The root yields 10% tannin[].

The wood is used for full[]. When groundwater levels start falling at the beginning of the dry season, the defoliated stems and branches are left and become dry. These dry materials are collected and utilized as firewood by the low-income people living in the vicinity of the reservoirs[]. The use of this material as firewood releases the wood harvesting pressure in the upstream area of the reservoir[].

Propagation

Seed - mature seed requires pre-treatment in order to break down the hard seed coat and allow the ingress of water[]. This can be done in various ways, including abrading the seed coat (being careful not to damage the embryo); immersing the seed in a small quantity of almost boiling water (which cools fairly quickly and so does not cook the seed) and then soaking the seed for 12 - 24 hours in warm water; the seeds also germinate profusely if they are subject to burning - though obvious care is required to ensure the heat is not too great and cooks the seed[]. Germination rates of 98% have been achieved from treated seed[].

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