Common Name: Black Mangrove

General Information

Black mangrove is an evergreen shrub or small to medium-sized tree with a rounded crown of spreading branches; usually growing 3 - 12 metres tall but occasionally reaching 25 metres[, ]. The bole, which is often crooked, can be 30 - 60cm in diameter[]. Growing in the tidal mudflats, the plant has developed roots with many vertical breathing roots above soil level[].
A multipurpose tree, it is harvested from the wild for use as an insect repellent, dye plant, source of tannins, timber etc.
Black mangroves are threatened by habitat conversion, pollution, hurricanes and other threats, which have resulted in declines throughout the wider Caribbean region. Although local estimates are uncertain due to differing legislative definitions of what is a 'mangrove' and to the imprecision in determining mangrove area, current consensus estimates of mangrove loss in the last quarter-century report an approximately 17% decline in mangrove areas in countries within this species range since 1980[]. It is currently classified as 'Least Concern' in the IUCN Red List of Threatened Species(2011)[].

Known Hazards

None known

Botanical References

Range

Tropical coasts of the Atlantic Ocean from Africa to the Americas and the Caribbean.

Habitat

Often common in mangrove vegetation in tidal estuaries, often on gravelly or sandy soils. It is most common on the landward side of mangrove swamps, in sheltered mud flats of tidal zones and at the mouths of rivers[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	10.00 m
Growth Rate	Medium
Pollinators	Bees, Ants
Cultivation Status	Wild

Cultivation Details

A plant of coastal areas in the tropics, where it is found at elevations up to 50 metres. It grows best in areas where annual daytime temperatures are within the range 20 - 30°c, but can tolerate 10 - 35°c[]. It can be killed by temperatures of -1°c or lower[]. It prefers a mean annual rainfall in the range 1,500 - 2,500mm, but tolerates 1,000 - 4,000mm[].
Requires a sunny position[]. Plants have a wide physiological tolerance to salinity, being able to survive in fresh stagnant water as well as in seasonally dry conditions with very high salinity[]. Prefers a pH in the range 6.5 - 7, tolerating 6 - 7.5[].
The leaves excrete excess salt through pores, and salt crystals are commonly present on the leaves[].
The seeds start germinating while still attached to the tree, but the embryo stays within the fruit until fruit fall[299[.
Young plants are moderately fast growing. In experiments in Ghana, seedlings reached a height of up to 26 cm at 4 months after planting. Under optimal growing conditions, trees may grow 60 cm/year in height[].
In many mangrove regions, the potential of this tree is considered limited and other mangrove species like Rhizophora spp. Are often more highly valued for timber, firewood, charcoal, dye and tannin production. Although mangroves are often heavily exploited, this tree is often left[].

Edible Uses

The cotyledons of the seed are eaten during famines, but only after careful preparation to remove toxic compounds[].

The leaves and roots are used to prepare a vegetable salt[]. It is said to be better than that made from other species of mangroves[].

Medicinal

An extract of leafy twigs of Avicennia germinans from southern Florida (United States) showed cytotoxic activity in several human cancer cell lines, with the naphthoquinone 3-chlorodeoxylapachol as active compound[].

Decoctions of the bark and leafy twigs are taken or added to a bath in order to promote childbirth[]. The powdered bark is made into a paste and applied externally to treat skin complaints and to dispel fleas and lice[].
The bark resin is used in traditional medicine to treat tumours, diarrhoea, haemorrhage, haemorrhoids, rheumatism, swellings, wounds and sore throat[].

The leaves are applied as an enema to treat piles[].

The stems and leaves are combined with a smaller amount of Rhabdadenia biflora and Nicotiana tabacum to make a soothing remedy for stingray wounds[].

The root is aphrodisiac[]. A decoction is taken to treat intestinal problems[].

The wood contains the naphthoquinone lepachol[].

Agroforestry Uses:

The flowers are a good source of nectar for honey bees, producing a quality honey[, ].

Other Uses

The bark has been used for tanning and for dyeing reddish colours[]. The bark contains about 12.5% tannin[].

A gum is obtained from the bark[].

Ash is added to water as a soap substitute[].

Smoke from the wood is reported to dispel mosquitoes effectively[]. Ethanol solutions of smoke from the burning wood inhibited the growth of pathogenic bacteria and fungi, such as Escherichia coli, Staphylococcus aureus and Saccharomyces cerevisiae[]. Moreover, the smoke significantly deterred Acraea acerata, a pest of sweet potato, from depositing eggs[].

The heartwood is pale brown to pinkish brown, darkening upon exposure, and rather indistinctly demarcated from the whitish sapwood[]. The wood is very durable, even under water; heavy; with a fine texture; and a grain that is often interlocked[]. It is difficult to air dry, being liable to twisting and checking. The rates of shrinkage are high, from green to oven dry about 7.1% radial and 10.2% tangential. Once dry, it is stable in service. The wood is difficult to split radially, but not tangentially. It saws satisfactorily, but is difficult to work by hand tools. It has some tendency to split upon nailing and screwing. It has been reported that the wood is suitable for particle board and pulp production, but for the latter purpose it should be mixed with wood of other species that have longer fibres[].
The wood is used for marine construction, boat construction (especially ribs), wharves, piles, house building, furniture and implements[]. It is also suitable for heavy flooring, mine props, railway sleepers, joinery, vehicle bodies, handles, ladders, toys, novelties and carving[].
The wood is also used as firewood and for charcoal production[].

Propagation

Seed - very subject to desiccation, the seed is best sown fresh, though they have been known to float in salt water for one year without rooting yet still be viable[]. Young seedlings grow best when they are in contact with fresh water, though older seedlings need contact with sea water[].
Natural regeneration is often abundant, and wildlings can be collected to serve as planting stock[].

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