Common Name: Algarrobo Blanco

General Information

Prosopis alba is a thorny, semideciduous tree with a rounded crown; it can grow 5 - 15 metres tall[]. The bole is short with many branches, but can be up to 100cm in diameter[, ]. Trees with straight boles 2.5 - 3 metres long can occur, but these are becoming extremely rare because they are being cut in preference to other trees with shorter boles[].
The plant is a valuable resource for arid areas, providing food, medicines and fuel. It is cultivated in parts of Argentina; is used in soil reclamation and conservation projects; and is also sometimes grown as an ornamental[, ].
In recent years this timber species has been heavily exploited, notably in Argentina. The population structure is reported to be fundamentally changed. The plant is classified as 'Near Threatened' in the IUCN Red List of Threatened Species(2011)[].

Known Hazards

None known

Botanical References

,

Range

S. America - northern Argentina, Paraguay, Uruguay, Bolivia and Peru.

Habitat

Arid and semi-arid regions with groundwater, such as drainage channels and along groundwater sinks. A common ruderal weed, coming up singly and in groups along roadsides, around habitations, on refuse dumps and in other disturbed habitats[].

Properties

Conservation Status	Near Threatened
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Semi-deciduous Tree
Height	10.00 m
Pollinators	Bees
Self-fertile	No
Cultivation Status	Ornamental, Wild

Cultivation Details

Prosopis alba is a plant mainly of the dry subtropical zone, extending into the tropics at higher elevations in Bolivia and Peru. (though it is found at elevations as low as 360 metres at latitude 18°S in Bolivia). It grows best in areas where annual daytime temperatures fall within the range 10 - 20°c, though it can tolerate 7 - 28°c and an absolute maximum of 45°c[]. Mature specimens can tolerate occasional short-lived temperatures down as low as -6°c, though younger plants can be killed at -1°c[]. It prefers a mean annual rainfall in the range 200 - 500mm, tolerating 100 - 700mm[].
Requires a sunny position[]. Succeeds in most soils so long as they are well-drained[]. Tolerates somewhat saline soils[]. Prefers a pH in the range 5 - 6.5, tolerating 4.5 - 7[]. Established plants are very drought tolerant[].
Under optimal conditions a large tree (40 cm in basal diameter and 7 m in canopy diameter) may produce 40 kg of pods[].
There are some forms of this plant that are thorn-free[].
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

Pod - fresh or dried[]. The pod can be eaten as a fresh fruit or conserved in its own sweet fresh juice[]. If the pod is dried then ground into a powder, it gives a flour that can be mixed with a little water and eaten immediately or used for making cakes[, ].
The var Prosopis alba panta Griseb., is said to produce the best seedpods - these can be up to 30cm long and 18mm wide, fleshy with a sweet flavour[].

The popular drink 'aloja' is prepared in Argentina with the fresh, sweet tasting pods[]. The mature or immature seedpods can be crushed and then fermented with cold water to make a good quality, beer-like beverage, and can also be used to distill stronger beverages.

The roasted seeds can be used as a coffee substitute[].

A gum obtained from the stems has a soft consistency and a sweet flavour. It is used as a candy[].

Medicinal

Leaf extracts have shown antibacterial activity[].

The seedpods are said to be very nutritions and, when eaten as a food, can help to dissolve stones in the bladder[].
A poultice meade from the crushed immature fruits (after the seeds have been removed) and the bark is used to treat bone fractures where there are no external wounds[].

The bark, branches, gum and foliage are antiseptic, antidysenteric and emollient[]. They are used as a treatment against gastritis[]

Agroforestry Uses:

The nitrogen fixing properties, rapid growth and deep roots make this a suitable species for erosion control and soil improvement[].
The tree is planted in reclamation schemes for salt-affected soils[].

Other Uses

A gum obtained from the trunk has physical and chemical properties similar to gum arabic (Acacia spp.)[].

The bark and leaves are rich in tannins[, ]. The wood contains 5 - 9% tannins[].

The heartwood is reddish-brown; the sapwood yellowish[]. The wood is fairly dense, hard, durable and difficult to work[, , ]. The wood is of high value within its natibve range, where it is used for a wide range of purposes including construction, parquet floors, doors and furniture[, , , ].
The wood is excellent for both firewood and charcoal[, , , ].

Propagation

Seed - it remains viable for several years in normal storage[]. The seeds are hardcoated and must be scarified in order to germinate. Burning, nicking and immersion in boiling water are some of the methods that can be used. If the seeds are not extracted from the pods before sowing, they will normally require several minutes of boiling to overcome dormancy. Normally the seeds are sown directly in containers. Germination starts after 2 weeks and continues for up
to one month. When the plants are 30 - 35cm tall they are ready for planting in the field[].
Direct seeding is also possible[].

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