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Avicennia germinans

Accession Count: 0

Common Name: black mangrove

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Family Name: Acanthaceae

Botanical Name: Avicennia germinans

Synonyms:

Family Synonyms: Verbenaceae

Sub Species:

Variety:

Forma:

Cultivar:

Characteristics: Avicennia germinans is a dense evergreen tree that possesses a bushy form and numerous upright pneumatophores, which provide oxygen to the underground root system (1, 2). The black mangrove is low-branching and can grow as high as 50 feet, but usually does not surpass 20-30 feet in height (2, 3). Younger trunks possess smooth, dark gray to black bark, while the bark becomes fissured and scaly in older trees (4, 5, 6). The lanceolate leaves are simple, opposite, and larger than other mangrove species, reaching 2-6 inches long (2, 7). Leaves are leathery and dark green in color, being silvery and hairy beneath, and occasionally accumulating white salt crystals on the leaf surface (2, 8). Year-round or in mid-summer, cone-shaped clusters will bloom at the end of branchlets, white and fragrant with yellow centers (2, 3, 5). Flattened, lima-bean shaped propagules will follow the inflorescence throughout the year, germinating while still attached to the tree (5, 6). These propagules split along the sides and contain a single seed (6).

Compound: Avi ger

Geographic Origin: Gulf of Mexico

Ecozone Origin:

Biome Origin:

Natural History: The black mangrove is native to Bermuda, the Caribbean region, small groupings within the Lucayan Archipelago, the southern United States (Florida), the gulf of Mexico, and the West Indies (8, 9). However, it is also distributed from Mauritania to Angola in tropical Africa, and along the coasts of Central and South America, in coastal and estuarine habitats (9). While the IUCN Red List currently considers black mangrove at “least concern” of extinction, populations are decreasing due to human activity. The species is protected in part of its native range, such as Bermuda, but an IUCN update is necessary on the world-wide status of A. germinans (8, 10).

Avicennia germinans was named by Carl von Linnaeus in 1764, where it was published within Species Plantarum (11). The genus, Avicennia, is named for the Iranian physician and philosopher Abu Ali Al-Husayn Ibn ‘Abd Allah Ibn Sina, who went by the alias Avicennia (980-1037 A.D.) (5). Germinans, the specific epithet, is named for the Latin germinare, to germinate (2, 5).

Cultivation Notes: A. germinans is hardy to USDA zones 9a to 11 (20-40°F), but observes the best growth at 68-86°F (3, 12). However, while the black mangrove is the most freeze-tolerant mangrove species in North America, it is still frost-tender and susceptible to damage when temperatures reach 24.8°F, with mortality occurring below 19.4°F (13). Additionally, the black mangrove must be kept in consistently moist conditions and is completely intolerant of long periods of drought, although seasonal drought is acceptable (12, 14). However, if kept moist, A. germinans is tolerant of most soils, including poor, sandy, loamy, and clay; and will survive a pH of 5.3-7.8 (4). At the same time, black mangrove tolerates flooding, salt winds, storms, and high saline or brackish conditions (1). To ensure the best growth, full sunlight is necessary – provide direct sun if possible (12, 14). Under optimal conditions, young plants will grow quickly, extending up to 2 feet each year (12).

Propagation is possible through softwood cuttings and seed, which should be sown after the last frost while still fresh (3, 12). Because black mangrove is cryptoviviparous, the embryo will emerge from the seed coat while still attached to the tree. The seedlings, or propagules observe the best growth when exposed to fresh water, while older seedlings require contact with sea-water (12). Generally, propagules can be planted and grown without difficulty, and are capable of surviving long periods in salt-water without rooting or perishing (1, 14).

Ethnobotany: Avicennia germinans is a keystone species that has been used extensively for medicinal, culinary, and cultural purposes. Medicine created from bark resin has been used within the West Indies to treat tumors, diarrhea, hemorrhage, swelling, wounds, sore throat, rheumatism, and hemorrhoids (9). When made into a tea, gastrointestinal and dermatological problems can be treated, while the root can also become an aphrodisiac (12, 15). At the same time, black mangrove is insect repellant - a paste made from powdered bark is capable of dispelling fleas and lice, while also curing skin conditions (9, 12). Further medicinal uses of A. germinans include the promotion of childbirth, as a remedy for stingray wounds, and as a potential treatment of cancer – especially cancer of the larynx and ulcers of the throat (12, 16).

While both the fruits and cotyledons are toxic, they can be consumed after careful preparation – in tropical Africa, the cotyledons are eaten during times of famine (12, 16). The honey that is harvested from the flowers is of excellent quality and is commonly cultivated (14). At the same time, Indigenous cultures value A. germinans as a source of salt, which is considered higher quality than that from other mangrove species (5, 12).

Gum can be obtained from the bark, which has also been used in tanning and the creation of dye. When burned, the wood can dispel mosquitoes, or be used as charcoal or firewood, while the ash can be added to water as a soap substitute. In addition, the wood has been used in marine, boat, house, and other construction (12). However, the wood is generally considered the least effective of the mangrove species (16). Lastly, when planted along river banks or in upland areas, A. germinans has value as a landscape or shade-plant (5).

Despite these ethnobotanical properties, the most important value of black mangrove is as a keystone species in aquatic and semi-aquatic environments. A. germinans traps debris beneath its roots, building shorelines and trapping nutrients for aquatic species to consume (5). At the same time, black mangrove provides a habitat and nursery environment for countless species, including wading birds, juvenile fish, pollinators, and invertebrates (1, 5). Finally, black mangrove filters runoff and decreases storm impacts to coastal communities by behaving as a buffer (1, 17). As a keystone species, the survival of A. germinans is integral to the health of coastal habitats.

Height: 20 - 50 feet

Width: 0 - 5 feet

Growth Rate: Fast Growing

Grow Season:

Flower Season: Summer

Color: White

Function: Shade

Spread: Non-spreading

Allergen: Non-allergenic

Invasive: Benign

Toxicity: Toxic

Hardy: Tender

Water Use: Moderate Water Use

Citations:

Smithsonian Marine Station at Fort Pierce. Retrieved February 4th, 2021.
Virginia Tech Dendrology. Retrieved February 4th, 2021.
Dave’s Garden. Retrieved February 4th, 2021.
Lady Bird Johnson Wildflower Center. Retrieved February 4th, 2021.
University of Florida. Retrieved February 4th, 2021.
Identification Guide to Marine Organisms of Texas. Retrieved February 4th, 2021.
Ocean Oasis Field Guide. Retrieved February 4th, 2021.
Department of Bermuda. Retrieved February 4th, 2021.
PROTA4U. Retrieved February 4th, 2021.
IUCN Red List. Retrieved February 4th, 2021.
Tropicos. Retrieved February 4th, 2021.
Useful Tropical Plants. Retrieved February 4th, 2021.
British Ecological Society. Retrieved February 4th, 2021.
Natives for Your Neighborhood. Retrieved February 4th, 2021.
Leon Levy Native Plant Preserve. Retrieved February 4th, 2021.
Purdue University Horticulture & Landscape Architecture. Retrieved February 4th, 2021.
New College. Retrieved February 4th, 2021.

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