Plants of Florida swamps

Some of the factors that determine which plants grow in a swamp are its hydroperiod, fire history, geographic location, water quality, and  level of human disturbance. The longer a swamp is filled with water, the more stressful conditions for become for plants.Therefore, swamps with shorter hydroperiods tend to have a greater variety of species, while swamps with long hydroperiods may be dominated by only one or two species.

Long hydroperiods are stressful because water covering swamp soils hinders oxygen uptake by wetland plant roots.  Many plants that can survive in swamps have developed unique adaptations for supplying oxygen to their roots. For example, cypress trees have developed pneumatophores, more commonly referred to as knees. Cypress knees are part of the root system that projects out of the water. They are thought to function like a snorkel, transporting air to submerged roots. Other adaptations for supplying oxygen to submerged roots are special roots called adventitious roots that grow out from the plant above the water and special spongy tissues called aerenchyma, which can transport air from plant parts above the water.

For many swamp plants submerged roots are not a problem. Swamps are home to numerous air plants like Spanish moss, butterfly orchids, and several ferns. Tree trunks, old stumps and fallen logs also provide elevated growing sites.   

Geographic location and temperature range are also key factors in determining which plants will grow in a swamp. Certain species of epiphytes are common to South Florida swamps but are unable to withstand the colder temperatures of North Florida. Melaleuca and Brazilian pepper, invasive non-native tree species, are also limited to warm, South Florida wetlands since they cannot tolerate freezing temperatures.

Cypress, the most common wetlands tree in Florida, is the dominant species in most swamps since it is highly flood-tolerant. However, cypress trees require occasional dry-downs to allow their seeds to germinate in the mucky, saturated soil. There are two types of cypress trees in Florida swamps. Bald cypress grows best in swamps along rivers and streams while pond cypress is found in still-water swamps. In areas of south Florida, for example Big Cypress Swamp and the Everglades, poor growing conditions stunt the growth of pond cypress. Cypress trees there only grow to about 10 feet tall and these wetlands are called dwarf or pigmy swamps.

Cypress trees can grow up to 150ft tall and live over 500 years. Native Americans often used them for dugout canoes because of their large size. Some canoes could hold up to thirty people. Early settlers logged much of the cypress timber from Florida swamps. The logs were floated down rivers, such as the Suwannee and the St. John ’s, and used for building homes and forts. Even into the early 1900s cypress wood was widely used for shingles, water pipes, and grave markers. Most of the cypress that is harvested today is sold as landscaping mulch and decorative lumber.  

Common swamp hardwoods include swamp tupelo, white and pop ash, loblolly bay, sweetbay magnolia, red maple, willow, sweetgum, and certain oaks. Common wetland plants such as cattails, arrowhead, yellow primrose, and pickerelweed with its bright purple flowers decorate the edges of the swamp.   Drier areas feature shrubs like holly, wax myrtle, and gallberry. Together these plants form an interesting and diverse natural community.

Not all of the plants that are found in Florida swamps are welcome residents. Several species of non-native trees and plants have managed to invade swamplands and threaten to displace much of the native vegetation. Melaleuca is one example of an invasive exotic tree that has already taken over thousands of acres of wetlands. These trees are both flood-tolerant and fire-resistant and they manage to recolonize easily and rapidly after a fire. This gives Melaleuca trees a competitive advantage over many native plants and allows it to spread very quickly.

Cypress knees are root projections that extend above the water and “snorkel” air to submerged roots.

Dwarf cypress dome in the Florida Everglades.