Florida's Marvelous Mangroves
Mangroves are so important for the health of the shorelines that Florida has passed regulations to govern their treatment. We mentioned mangroves last week as one of Florida's important water resources and habitats in We ALL Live in a Watershed!
|Mangroves as far as you can see at Pennekamp State Park on Key Largo.|
The term mangrove describes either a single species or the whole plant community that grows along saline shorelines. These plants are not related taxonomically, but are grouped by their ability to grow at the edge of the sea. There are 50 species worldwide, but only three mangrove species are native to Florida: red, black, and white, and because it so often grows in the same habitat, another native, green buttonwood, is often thought of as Florida's unofficial mangrove. The mangrove ecosystem ranges from shallow waters into the shore. Typically the red mangrove with its built-in stilt-like roots grows farthest out in the water, followed by black and then white as you move toward shore. The green buttonwood grows mostly on dry land, but can withstand periodic flooding.
|Red mangrove propagules.|
One of the features that all mangroves share is that their seeds germinate while still attached to the parent tree—this is called viviparous germination or viviparity. Once germinated, the seed forms a propagule, a seedling that has roots, a stem, and leaves. When dropped, it can float away vertically, root-end downward, until it lands on a favorable site where it can quickly send out roots to anchor itself. The leaves and green stem are already capable of photosynthesis at the point of landing and can provide the energy necessary to fuel the quick root penetration. A propagule may float for many months with no ill effects.
|Red mangroves have stilts for roots and occur|
farthest out from the shoreline
If your property or property in your community abuts a body of water, consider mangroves for your waterfront instead of, or in front of, a bulkhead or other shoreline hardscape. They provide beauty and habitat, but maybe most important for waterfront property owners, mangroves protect the shoreline from wave-induced erosion and stormwater erosion from the land. Mangroves also absorb nutrients that may run off the land, which improves the overall water quality.
Mangroves are protected species in Florida and you are not to trim them back if they are over ten feet tall or collect them from the wild—not even a propagule that may float by. There are a number of sources online that service the aquarium trade, but be sure to purchase only the four Florida natives mentioned here and for the greatest chance of success, purchase propagules instead of seeds. Mangroves are usually available from nurseries that specialize in native plants.
|Black mangroves and their pneumatophores|
Plan for the adult size of these trees, which may eventually reach 30 to 40 feet or more; so don't plant under low overhead wires, and leave at least three feet between them. Bury one third of the propagule in the mud. You sometimes see mangroves planted in a regular checkerboard pattern, and while this spacing will eventually be obscured as the mangroves mature, wouldn't it be better to plant them in a more random pattern so it looks like Mother Nature has arranged them?
If the planting site receives continuous wave action, you'll need to fashion some type of anchor and probably some type of protection to keep the new mangrove seedlings from being washed away or damaged by the flotsam and jetsam until they become established. Some folks use a cylinder of galvanized hardware cloth attached to a deeply driven stake to surround the seeding and keep it in place--others use a PVC pipe. This cylinder also protects young seedlings from raccoons, deer, and other munching critters. Plan to remove the cylinder later as the tree grows, but other than that, no particular care or fertilization is required.
|At Blowing Rocks: White mangrove is in|
foreground; black mangrove is darker behind it.
Blowing Rocks, a Nature Conservancy preserve, in Jupiter has ongoing mangrove restoration projects. Andrea Graves summarized them:
"We consider the mangrove and tidal creek restoration along the Lagoon Boardwalk to be very successful. This habitat contains all three species of mangroves found in Florida: red, black and white. After the initial restoration in the mid-80’s, many of the trees you see today moved in on their own and colonized the area, a process known as natural recruitment. Another sign of success is the large number of fiddler crabs that can be observed at low tide foraging in the detritus. The falling leaves from the mangroves decay and form the base of the food chain for the Indian River Lagoon. We often see wading birds such as white ibis or little blue herons, feeding on the fiddler crabs in these mangrove wetlands. In addition to their habitat value, mangroves help reduce shoreline erosion and improve water quality by filtering pollutants.
|White mangrove leaf.|
Note the indentation at the tip.
|Buttonwood branch with fruits. Buttonwood is not a|
mangrove, but it often grows inland from mangrove forests.
Because the propagules can float in the sea for so long, they can be the first plants to become established on a newly emerged sand bar. Over the years the mangroves form thickets of vegetation, then birds come to roost bringing more types of seeds. Meanwhile oyster spat cling to the mangrove roots, fish and crabs find habitat amongst the roots, and a whole new island ecosystem has formed. Without the mangrove as a pioneer, it would still be a sandbar that could erode away at any time.
Be a pioneer in your neighborhood and establish some wondrous mangroves along the shorelines. You might be rewarded with some roseate spoonbills nesting in the mangrove thickets and soaring bald eagles. Now wouldn't that improve your view??
|A buttonwood tree with its peeling bark.|
Buttonwoods are a good addition to
south Florida landscapes
Mangrove trimming regulations: www.dep.state.fl.us/southwest/erp/mangroves.htm