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Rhizophora spp.

true mangroves

Rhizophoraceae

Tropical and subtropical coasts worldwide

Attracts Pollinators

Native to North America

SunFull Sun

WaterHigh

HardinessZones 10–11

Overview

Rhizophora spp. is a genus of about eight to nine species of evergreen mangrove trees and shrubs in the family Rhizophoraceae, known as the true or red mangroves. They grow along sheltered tropical and subtropical coasts, lining estuaries, tidal creeks, and lagoons in soft, waterlogged, salty mud. Mature trees reach 15 to 100 feet (5 to 30 m) tall depending on species and site, supported by arching stilt or prop roots that rise from the trunk and lower branches into the mud. The thick, leathery, elliptic leaves are 3 to 7 inches (8 to 18 cm) long, dark green above and paler beneath. Small, pale yellow to cream four-petalled flowers are followed by viviparous seeds: each germinates while still attached to the parent, forming a long, cigar-shaped propagule up to 12 inches (30 cm) long that drops and roots in the mud or floats to new ground. Red mangroves stabilise shorelines, build land by trapping sediment, and shelter fish, crabs, and birds. They are confined to frost-free coasts and are killed by hard freezes, and their salt-excluding roots require regular tidal flushing.

Native Range

Rhizophora spp. occurs on tropical and subtropical coastlines worldwide. Species line the shores of the Americas, West Africa, the Indo-Pacific, Southeast Asia, and northern Australia. In North America the red mangrove, R. mangle, fringes the coasts of Florida, the Gulf of Mexico, and the Caribbean.

Suggested Uses

Red mangroves are used in coastal restoration, shoreline stabilisation, and erosion control across the tropics, and they underpin estuarine fisheries by sheltering young fish and shellfish. In aquaculture and large marine aquariums they are grown to filter nutrients from the water. They are unsuited to conventional gardens away from tidal salt water.

How to Identify

Look for evergreen coastal trees standing on a cage of arching stilt roots that lift the trunk above the mud. The leaves are thick, leathery, and elliptic, 3 to 7 inches (8 to 18 cm) long. The clearest sign is the long, narrow, pencil-shaped propagule that hangs from the branches, a pre-germinated seedling carried by no other mangrove group in the same form.

Appearance

Size & Dimensions

Height15' - 100'

Width/Spread10' - 30'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~20 weeks

Spring Summer

Flowering occurs through much of the year in the wet tropics, with peaks that vary by region and species. In Florida, R. mangle flowers mainly from spring through summer. The pale flowers are followed over many months by the long hanging propagules, so flowers and developing seedlings often appear together.

Detailed Descriptions

Flower Description

Pale yellow to cream

Foliage Description

Dark green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 8-12 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 Range6.0 - 8.5(Alkaline)

357912

Soil Types

silt clay sand

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

tender

Time to Maturity

Reaches reproductive size in 5-10 years

Care & Maintenance

Care Guide

Rhizophora spp. grows in the intertidal zone of warm coasts, rooted in soft, anaerobic, saline mud that is flushed by the tides. The trees need constant warmth and are killed by frost, restricting them to roughly USDA zones 10 and 11. They tolerate full salt water as well as brackish conditions, excluding most salt at the roots. Outside their natural habitat they are difficult to grow, needing salt water, tidal movement, and high humidity that ordinary gardens cannot supply. Propagation is from the fallen propagules, which root readily when pushed into wet mud. Growth is slow to moderate, and trees are sensitive to oil, pollution, and changes in water flow.

Pruning

Pruning is rarely undertaken in natural stands. Where mangroves are managed along waterways, branches are trimmed lightly to maintain clearance, but heavy cutting can kill the tree because it does not resprout strongly. Removal of the prop roots damages the support system and is avoided.