The Everglades is a vast, subtropical wetland ecosystem defined by its slow-moving sheet of water that flows south from Lake Okeechobee toward Florida Bay. A gradual gradient of salinity and elevation dictates the location and composition of its tree communities. The “River of Grass,” dominated by sawgrass marsh, is interspersed with pockets of dense forest and isolated tree islands, whose species makeup depends entirely on the region’s complex hydrology.
Coastal Tree Communities Mangrove Forests
The transition from freshwater marsh to the marine environment is marked by extensive mangrove forests, the primary tree life in the brackish and saltwater zones. These salt-tolerant trees stabilize the coastline and thrive in the intertidal zone where few other species can survive daily tidal fluctuations. The three main species exhibit a distinct zonation pattern based on their tolerance to salinity and specialized root adaptations.
The Red Mangrove (Rhizophora mangle) grows closest to the water’s edge, identified by its arching, reddish prop roots that extend from the trunk and branches, giving the tree a stilt-like appearance. These roots offer physical stability in soft, anaerobic sediments and filter out up to 97% of the salt from the water. Slightly further inland, the Black Mangrove (Avicennia germinans) occupies areas with less frequent tidal flushing and higher elevation. This species uses specialized, pencil-like root projections called pneumatophores that emerge vertically from the mud to acquire oxygen for the submerged root system.
The Black Mangrove excretes excess salt through glands on the surface of its leaves, which often leaves a visible white residue. Furthest inland, the White Mangrove (Laguncularia racemosa) typically lacks the elaborate root structures of the other two species. It manages salt by concentrating it in old leaves that are eventually shed, and it is considered the least salt-tolerant of the three. These three species form the largest contiguous stand of protected mangrove forest in the Western Hemisphere, protecting the coast from storm surges and acting as a marine nursery.
Freshwater Swamp and Slough Trees
Moving away from the coast, the permanently or semi-permanently flooded freshwater areas are dominated by the Bald Cypress and its close relatives. The Bald Cypress (Taxodium distichum) is a deciduous conifer uniquely adapted to thrive in standing water, often growing in circular formations called cypress domes. In these domes, the tallest trees grow in the center where the limestone solution hole is deepest, with tree size gradually decreasing toward the drier edges.
Bald Cypress trees have massive, buttressed trunks that provide stability in the soft, waterlogged soil. They also produce structures known as cypress “knees,” which are woody projections that rise above the water surface from the root system. While their purpose is debated, these knees may help anchor the tree or facilitate the exchange of gases with the atmosphere. In areas with nutrient-poor soil and shallow water, the Pond Cypress (Taxodium ascendens) grows in a stunted form, often referred to as Dwarf Cypress. These slow-growing trees remain small and thin, contrasting sharply with the stature of the Bald Cypress found in richer, deeper swamps.
Upland and Elevated Island Trees
The greatest diversity of tree species is found in scattered elevated areas that remain largely dry, falling into two distinct communities: the Pine Rocklands and the Hardwood Hammocks. The Pine Rocklands are characterized by a thin layer of soil over porous limestone bedrock, dominated by the Florida slash pine (Pinus elliottii var. densa). This pine subspecies possesses thick bark and long needles that protect its vulnerable buds, representing an adaptation for survival in a fire-dependent ecosystem.
The life cycle of the Florida slash pine is tied to regular fires, which historically occurred every three to seven years due to lightning strikes. Fire is necessary to clear the understory and eliminate competing hardwood saplings, preventing the habitat from transitioning into a dense hammock. Without periodic burning, the pine rocklands would be overtaken by shade-tolerant hardwoods, a process known as succession.
The second upland community, the Hardwood Hammock, forms dense, diverse islands of tropical trees growing on slight elevations of limestone or peat. These “hammocks” are essentially tropical forests that grow high enough to escape the frequent flooding of the surrounding wetlands.
These oases feature a variety of tropical hardwood species, including the Gumbo Limbo (Bursera simaruba), with its peeling, reddish bark, and the Strangler Fig (Ficus aurea). Other common species include Live Oak, Hackberry, and various palms, creating a dense canopy that shades the ground. These elevated islands serve as refuges for wildlife during high-water periods. The hammock’s composition is protected by its slightly higher elevation, which keeps the area dry and prevents the spread of natural fires that sweep through the adjacent pine rocklands and sawgrass marsh.