Name:
Mesquite (Prosopis spp.)
Description
The various Mesquite species (Prosopis spp.) come in a range of shapes and sizes. They can be found
as multi-stemmed shrubby bushes or single stemmed trees with a spreading canopy often with an
irregular outline with some branches protruding out of the canopy, growing from 3 to 15 m tall. The
bark is smooth and dark red-green in young stems, and rough and grey in older stems. Branches have
a characteristic zig-zag structure, and the overall impression is of a rather untidy plant, with single
branches extending outside the main canopy. Mesquite leaves occur at each point where the branch
changes direction (the zig-zag) and are compound (twice-divided), with 1-4 pairs of primary leaflets
each with 7-21 pairs of small opposite secondary leaflets. There are often one or two thorns at the base of the leaves.
The greenish cream-yellow flowers form a cylindrical flowerhead 50-80 mm in length. Pods are 5-20
cm long, compressed, straight to curved, smooth or with slight restrictions between the seeds. Ripe
pods are yellow, purple, or yellow with purple streaks and patches. The flat seeds are oval or
elliptical 2.5-7 mm long by 2-3 mm wide, each enclosed in a flattened fibrous case, and surrounded
by sweet pulp.
Identification of Mesquite species is complicated because there is often variation in growth form,
even within the same species, and hybrids between the main species are common. For further
information and assistance with identification of Mesquite contact the herbarium in your state or
territory.
Distribution:
There are four naturalised species of Mesquite in Australia, and a range of hybrids. Collectively, they
are suited to the climate of much of inland Australia. The worst infestations are on pastoral land in
the Pilbara in Western Australia, the Barkly Tablelands in the Northern Territory, and in north-western,
central and south-western Queensland.
Different species have different distributions, which reflect their initial plantings but also variation in
their preferred climate and surroundings. For example, Prosopis pallida is widely distributed across
the north of Australia from the east coast of Queensland through the Northern Territory to the west
coast of Western Australia. However, it is not found in any of the southern states, whereas Prosopis
velutina and the hybrid P. velutina x P. glandulosa var. torreyana can tolerate the cooler climate of
southeastern Australia.
Habit:
Tree, Shrub
Key points:
- Mesquite (Prosopis spp.), which includes four species and several hybrids, is one of four prickle bushes that have infestations scattered throughout semi-arid Australia.
- It is a nuisance in rangelands where it forms dense impenetrable stands, particularly around waterways.
- Animals eat the seed pods and spread the seeds. Historical control efforts by mechanical and chemical means have been expensive and ultimately ineffective.
- Control requires an integrated management approach, including mechanical, chemical and biological techniques and the use of fire and grazing strategies.
How it spreads:
Mesquite mainly reproduces via seeds, producing one main crop annually. Each seed pod generally
carries between 5 and 20 seeds, with potentially hundreds of thousands of seeds produced per
mature plant. Humans have assisted the spread of Mesquite throughout Australia and the rest of the
world.
Animals consume the nutritious seed pods and excrete viable seed in their droppings, helping to spread Mesquite over shorter distances. Cattle are mainly responsible, although horses, pigs, goats, sheep, emus and kangaroos are also known to consume the seed pods. As long as the seeds themselves are not damaged by chewing, digestion actually helps germination, particularly as the expelled seeds are deposited in moist, nutrient-rich dung. Apart from deliberate plantings, animals - mainly cattle - are most responsible for spreading Mesquite. Seed pods can also be spread by flooding.
Where it grows:
In general, Mesquite species are well adapted to hot climates and a wide range of soil types and annual rainfall (150-1200 mm). They can tolerate droughts and waterlogging, low nutrient soil and highly saline or alkaline soil. In northern Australia, Mesquite prefers semi-arid to arid rangelands that are prone to flooding and soils that have good moisture retention.
Flower colour:
Green, Yellow
Distribution map:
Impacts:
Mesquite is a Weed of National Significance. It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. Environmental impacts include land erosion resulting from the loss of grassland habitat that supports native plants and animals; and the provision of safe refuges for feral animals such as pigs and cats. Mesquite can also increase land degradation and loss of soil moisture due to its extensive and deep root system.
Mesquite’s economic impacts stem from its habit of forming dense, impenetrable thickets which, combined with its large thorns, prevent stock accessing watering holes and make mustering difficult. Mesquite also reduces the productivity of pastoral country by taking over grasslands and using valuable water resources. The sharp thorns damage animal hooves, puncture vehicle tyres, and inflict injury to people. Livestock which consume excessive amounts of seed pods can be poisoned.
Origin:
Mesquite species that are weeds in Australia are natives of Central America, northern South America and southern North America
