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Avicennia spp.

black mangrove

Acanthaceae

Tropical and subtropical coasts worldwide

Attracts Pollinators Fragrant (light)

Native to North America

SunFull Sun

WaterHigh

HardinessZones 10–12

Overview

Avicennia spp. is a genus of evergreen mangrove trees and shrubs in the family Acanthaceae, comprising about eight species of tropical and subtropical tidal coastlines. Plants range from low shrubs 3-10 feet (1-3 m) tall at range limits to trees 30-50 feet (9-15 m) in equatorial estuaries. Leaves are opposite, leathery, elliptic, 1.5-4 inches (4-10 cm) long, green above and pale or grey beneath, and excrete salt through glands that often leave a white crust. Roots produce upright, pencil-like pneumatophores that project 4-12 inches (10-30 cm) above the mud for gas exchange in waterlogged soil. Small flowers, 0.2-0.4 inch (5-10 mm) across, are yellow to orange and clustered at the branch tips. The fruit is a flattened, grey-green capsule about 0.8-1.5 inches (2-4 cm) long that germinates while still on the tree or shortly after dropping. Plants are evergreen and tolerate full-strength seawater, but are killed by hard frost. Growth is slow to moderate in the saline, oxygen-poor substrate.

Native Range

The genus occurs on tropical and subtropical coasts worldwide, including the Americas, Africa, southern and eastern Asia, and Australasia, with A. marina the widest-ranging species. Plants grow in the intertidal zone of estuaries, lagoons, and sheltered shores, rooted in saline mud between mean sea level and high-tide level.

Suggested Uses

Planted in mangrove restoration and shoreline stabilization projects along tropical and subtropical estuaries, spaced 3-6 feet (1-2 m) apart. Stands form nursery habitat for fish and crustaceans and buffer coasts against storm surge. The genus is rarely used as an ornamental and needs tidal saltwater conditions to persist.

How to Identify

Recognized as coastal salt-tolerant shrubs or trees with opposite, leathery leaves that are grey and salt-crusted beneath. The surrounding mud is studded with upright, pencil-like pneumatophores radiating from the trunk. Small yellow to orange four-lobed flowers appear at the shoot tips, followed by flattened grey-green capsules that often sprout a seedling before falling.

Appearance

Size & Dimensions

Height3' - 50'

Width/Spread5' - 20'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Spring Summer

Flowering occurs mainly in the warm season, from late spring through summer in subtropical regions and over a longer span near the equator. Flowers open over several weeks and are visited heavily by bees. Capsules develop through summer and autumn and may germinate on the branch.

Detailed Descriptions

Flower Description

yellow to orange

Foliage Description

green above, grey beneath

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.5 - 8.5(Alkaline)

357912

Soil Types

clay silt sand

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

tender

Time to Maturity

5-10 years

Care & Maintenance

Care Guide

Plants require full sun and saline, waterlogged tidal soils, and are grown chiefly for coastal restoration rather than ornamental settings. Salt water is tolerated up to full seawater strength, and the roots depend on tidal flushing for oxygen through the pneumatophores. Establishment is from propagules pushed into soft intertidal mud, with seedlings vulnerable to wave action and crab grazing in the first year. Plants are damaged below about 28 F (-2 C) and do not survive sustained frost. Few pests trouble established stands, though defoliating insects and wood-boring beetles occur. Growth is slow in cooler or hypersaline sites.

Pruning

Pruning is rarely carried out, as plants are grown for coastal protection rather than form. Dead or storm-damaged wood can be removed above the tideline. Cutting below the lowest leaves seldom resprouts, so hard cutting-back is generally not done.