Author’s Note: “Mangrove” generally refers to the habitat or biome and all trees and tall shrubs in the mangrove forest or swamp. Specific species of mangroves can belong to several genera and families of flowering plants. Scientifically, they are remote and only called mangroves because of their ecological function as buffers between areas of marine and terrestrial life.
There are four species of tropical to subtropical mangroves that protect Florida’s coastline, tidal estuaries, and salt marshes from erosion, storm surge, flooding, wind, waves, and hurricanes.
Globally, there are about 73 species or hybrids of mangroves in several families growing in about 123 countries. Due to coastal development, agriculture, industrial land use and human misunderstanding, mangrove ecosystems have been degraded and removed to the point that several species are now endangered or threatened around our Earth.
Salt-tolerant mangroves are called halophytes. They evolved to live in coastal salt and brackish water conditions. thus developed complex salt filtration systems and adaptable root systems to deal with saltwater immersion and wave action. Mangroves are adapted to waterlogged mud and sand with low levels of root oxygen. Tree branches and leaves tolerate salt spray above the roots in the intertidal zone. Sediment, human waste and pollutants are trapped among the roots and their own leaf litter adds carbon-rich organic matter.
With their roots often flooded with salt water, mangrove groves and forest are rich, diverse and productive ecosystems that provide habitats for plants and nurseries for many land and sea creatures, crabs, fish, molluscs , from birds, butterflies, reptiles and amphibians to mammals and insects. Mangroves filter waterborne pollutants and trap sediment, mud and sand.
Fort Island Gulf Beach and the protected salt marshes and estuary east of it support all four native Florida mangrove species in undisturbed and disturbed habitats. All four range from Levy County and Volusia County south around the Florida peninsula with some scattered areas for the two most cold hardy species on Escambia County and the steep coasts. .
Red mangroves (Rhizophora mangle), the most common mangrove species along the Atlantic and Gulf Coast or Mexico in the Americas, are easily recognized by their aerial or exposed stilt roots. These trees can grow up to 30 feet tall. Prop roots can take in air and leaves can excrete salt. They are among the first trees to colonize mud and sandbanks still inundated by the sea and are generally the species closest to water.
The opposite, long, oval, thick, leathery evergreen leaves are 2 to 6 inches long and have short petiole stalks. Pale yellow flowers can appear all year round. The red mangrove has foot-long fruit pods with seeds inside. While still attached to the tree, the embryonic roots emerge and rapidly grow downward. When the propagule pods drop, the roots grow in the mud or the pods may float on the tide to find a suitable place to grow. Once the roots of the pods are anchored in the ground, the first leaves begin to grow. Red mangrove pods can float and remain viable for up to a year. The fruit is sweet and nutritious.
Black mangrove trees (Avicennia germinans) grow on slightly higher, less flooded coastal land. Look around under the canopy to see pencil-shaped respiratory roots called pneumataphores protruding out of the sand or mud. These have small lenticel openings for air to enter and pass through the soft, spongy tissue to the roots below. The fruit is a small, flat, rounded pod. The roots develop while the fruit is still on the tree. As they fall, roots can anchor and grow or fruits can drift across the sea to land in a new home.
White Mangrove, (Laguncularia racemose) of the Combretaceae family, extends along the peninsular coasts of Florida, but is the least hardy to cold. It can quickly reach a height of around 50 feet. The leaves of the white mangrove are rounded at the base and tip and are smooth below. Each leaf has two nectarine glands at its base which secrete sugar. The insects feed on the excreted sugar. The white mangrove can have cone-shaped pneumataphores and/or tall, arching roots depending on the habitat.
Buttoned mangrove (Conocarpus erectus), from the Combretaceae family. protects tropical and subtropical coasts worldwide. Originating in tropical coastal America, it now extends from Bermuda to Brazil, around the warmer tropical coasts of the Gulf of Mexico and along the Pacific coast (from Mexico to Peru and the Galapagos Islands), to the west coast of tropical Africa.
A long-lived, evergreen perennial tree, it grows 20 to 40 feet tall. The yellow-green flowers grow year-round, attract pollinators and butterflies, and produce showy brown fruits. Hurricane resistant, it tolerates salt water flooding. Use as a specimen, shade tree in full sun or light shade and on moist to wet alkaline soil and occasionally flooded or irrigated.
Propagation is by seed and cuttings and Button Mangrove is available in the warm South Florida Coastal Zone 11. The seeds float for dispersal and it is a butterfly/caterpillar host plant for the nectar plant Amethyst Hairstreak (Chlorostrymon maesites ) and the pollinator attractor.
Jane Weber is a professional gardener and consultant. Semi-retired, she cultivates thousands of native plants. Visitors are welcome to his garden in Dunnellon, County Marion. Contact her at [email protected]