Rhizophora mangle can grow to heights of 70 and 80 feet in the tropics, but in South Florida and the Caribbean, they grow as shorter shrub like trees reaching heights of about 20 feet.
The red mangrove survives in saltwater of up to 44 parts per thousand, and has been found in areas where soil salinity is around 60ppt, a salinity level that would be lethal to most plant species. The red mangrove is found closer to the water than the other species of mangroves due to this high salt tolerance. The red mangrove is referred to as a ‘salt-excluder’. It prevents saltwater from even entering by filtering it out at the roots.
The prop roots, characteristic of the red mangrove, enable it to advance seaward from the coast and grow in waters of up to 3 feet in depth. These tall arching prop roots, which also supply air to underlying roots, provide stability to Rhizophora mangle and help to prevent erosion on the coastal line. The maze of prop roots trap silt and sediment that flows with the tide; this sediment will gradually build up and over time the shoreline can be increased as a result. Pores in the bark of the prop roots, called lenticels, allow the red mangrove to absorb air.
The shed leaves from the red mangrove also get collected by the prop roots and lead to a rich build up of organic detritus that help to provide an essential nursery habitat. Juvenile fish thrive in the mangrove channels, and commercially important marine species such as crab and spiny lobster also find shelter.
Rhizophora mangle is a viviparous plant. This means the seeds germinate whilst attached to the tree, instead of in the soil, like most plants. The germinated seedling called a propagule then grows out from the fruit; it is narrow and conical and grows to about 6” in length. The propagule will eventually drop from the parent tree and set root in the soil in which it lands; the propagule is hardy though and can float with the current for up to two years before settling in a suitable area and rooting.
The red mangrove has been reported to have medicinal and edible properties.
Medicinal uses of Rhizophora mangle include using the powdered leaves to relieve constipation and a tea brewed from the leaves to treat fish poisoning. The bark is high in tannin giving it astringent and expectorant properties that have been used to treat hemorrhage, inflammation, diarrhea, dysentery, leprosy, elephantiasis, syphilis, sore throat, fever and tuberculosis.
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