Buttonwood Mangrove (Conocarpus erectus), is a mangrove shrub in the family Combretaceae. Although it is not classified as a true mangrove, it grows where other mangroves do and their importance in coastal ecosystems is undeniable.
These resilient shrubs thrive in coastal environments, playing a vital role in protecting ocean shorelines, supporting marine biodiversity, and mitigating climate change impacts. From acting as a natural barrier against erosion and storm surges to providing habitats for various marine species, buttonwood mangroves are essential to the health of our oceans.
- Scientific name: Conocarpus erectus
- Common name(s): Buttonwood
- Family: Combretaceae
- USDA hardiness zones: 10B through 11
- Origin: Native to Florida, the Caribbean, and South America
- UF/IFAS Invasive Assessment Status: Native
Appearance
The buttonwood mangrove is a medium-sized tree that grows to about 30 feet tall. However, it has the potential to reach 66 feet or more. It is a a low-branching tree, multi-trunked, evergreen, medium tree, or large shrub with an open crown to dense crown with pruning. Its leaves are alternate, 2-4 inches long, leathery, and covered with silvery hairs.
- Growth Rate: Moderate
- Tree Shape: Spreading, Vase
- Canopy Symmetry: Symmetrical
- Canopy Density: Medium
- Canopy Texture: Fine
- Height at Maturity: Typically grow as medium-sized trees or large shrubs, reaching heights of 30 to 45 feet (8 to 15 m)
- Spread at Maturity: 8 to 10 meters (20 to 30 feet)
Buttonwood mangrove bark is scaly, ridged, and dark brown. When exposed to wind regularly, the trunk develops a unique gnarled and twisted shape.
The leaves are alternate, leathery, and covered with silvery hairs, measuring 2-4 inches in length. The green variety features shiny, dark green leaves, while the silver variety has a distinctive silver sheen due to dense pubescence.
Small, greenish flowers bloom in dense cone-like heads in the spring, followed by ½-inch, cone-like fruits that are purple-brown to red.
Varieties
Green Buttonwood: Buttonwood mangroves are well distinguished by their leaves. The leaves of the green buttonwood are long, oval, and alternating. On the upper side, the leaves are shiny and dark green, while the underside is pale green with thin hairs.
Silver Buttonwood: The silver buttonwood leaves are roughly the same shape as the green buttonwood. They are, however, silver in color and more hairy. The leaves of buttonwood mangroves also have small salt glands on the leaf surface. These glands help the tree excrete excess salt.
The silver variety, Conocarpus erectus var. sericeus, is slightly less cold-tolerant than the typical species. This variety is covered in fine, dense pubescence, giving the plant a distinctive silver sheen and color. However, it can attract a black discoloration that resembles sooty mold.
Habitat
Buttonwood Mangroves are generally found on the landward edges of mangrove forests. They thrive in drier conditions away from water, often acting as a natural hedge and buffer. Even so, it is a very handy tree, tolerating a wide range of conditions.
Despite their preference for drier habitats, these trees can tolerate a wide range of environmental conditions like brackish waters, muddy or sandy substrates by forming extensive root systems, making them a resilient species and stabilizing the soil.
Buttonwood mangroves often grow with other mangrove species, which include red, black, and white mangroves. Typically, it grows farther inland than all three true species of mangroves and is an excellent buffer system for winds, pollution, and storm surges.
While they are found in warm tropical and subtropical regions worldwide, they are native to the Caribbean, South Florida and Bermuda, and South America coastal areas and western Africa. Besides, they are also grown in inland habitats like yards and parking lots.
Environmental Tolerance
Buttonwood Mangroves are known for their high tolerance to salinity and adaptability to various soil types, including clay, sandy soils, loam, alkaline, acidic, wet, or well-drained soils. They grow in brackish waters, estuaries, and tidal creeks along the coasts of tropical and subtropical regions.
- Salt Tolerance: High
- Light Requirement: Full sun
- Drought Tolerance: High
Reproduction
Reproduction in buttonwood mangroves is both sexual and asexual.
Sexual Reproduction: The tree reproduces sexually by producing small, unisexual flowers. The wind or insects pollinate these flowers. Once the flowers are pollinated, they develop into fruits. The fruits are usually small, round, and green. As they mature, they transition from green to dark brown. They eventually fall from the tree and float on water until they reach a suitable substrate for germination. It is worth noting that each fruit contains a single seed.
Asexual Reproduction: The buttonwood mangrove also reproduces asexually through vegetative propagation. In this case, new plants may grow from the existing root systems. Also, new plants may sprout from the small twigs or branches that have fallen off and taken root. Sometimes, when in adversity, buttonwood mangroves may produce adventitious roots or shoots. If these roots or shoots come into contact with the soil, they may develop into new trees.
Role in Coastal Ecosystems
Buttonwood mangroves are integral to coastal ecosystems, often found at the landward edges of mangrove forests where they create natural barriers against ocean forces such as storm surges, tidal waves, and erosion. These resilient shrubs stabilize soil and contribute to the formation of coastal buffers that protect both marine and terrestrial ecosystems. In addition, buttonwood mangroves contribute to carbon sequestration, helping to offset climate change impacts on marine environments.
Ecological Importance in Marine Biodiversity
Buttonwood mangroves provide habitats for a wide range of coastal and marine wildlife. These trees offer shelter for bird species, crabs, and fish, while their flowers attract a variety of insects, supporting the entire marine food web. Furthermore, their root systems offer spawning grounds for marine life and act as nurseries for juvenile fish, making them vital to the overall biodiversity and health of coastal ecosystems.
They provide habitats for several species of birds, crabs, and mammals. The flowers, leaves, and rough bark of the plant attract various insects and spiders, which, in turn, serve as food for insect-eating birds. It occasionally acts as a larval host for Martial Hairstreak (Strymon martialis) butterflies and Tantalus Sphinx (Aellopus tantalus) moths, and it serves as a nectar plant for Amethyst Hairstreak (Chlorostrymon maesites) and other butterflies. The seeds are primarily dispersed by water.
Climate Change Mitigation
Coastal habitats, including mangroves like buttonwood, are critical in addressing climate change. Buttonwood mangroves contribute significantly to carbon storage, absorbing and storing carbon dioxide, thus acting as carbon sinks. By helping to reduce atmospheric CO2 levels, these plants protect both marine ecosystems and coastal communities from the effects of rising sea levels and extreme weather events caused by climate change.
Enhancing Coastal Protection
The ability of buttonwood mangroves to withstand strong water currents and act as a buffer against oceanic forces is vital for coastal protection. As rising sea levels threaten shorelines worldwide, buttonwood mangroves help reduce the impact of tsunamis, floods, and hurricanes, protecting both human settlements and marine life.
Commercial Uses
- In the past, the wood of the buttonwood mangrove was used for shipbuilding as it is durable and rot-resistant.
- Today, its buttonwood mangrove wood is used for various purposes, such as making furniture, flooring, and decorative items. It is also used in landscaping. This is because it is hardy and grows in a wide range of conditions.
- Some parts of the tree are used for medicinal purposes. In particular, extracts from the bark, leaves, or roots are used for treating various illnesses.
Conservation
Like all mangrove species, the buttonwood mangrove is threatened by a number of factors, such as habitat loss, pollution, and climate change. Coastal development, such as the construction of marinas and waterfront homes, endangers their survival.
Pollution from runoff and oil spills harms them too. Not only that but climate change, such as rising sea levels and increased storm activity, further degrade these coastal ecosystems.
Fortunately, as of today, several conservation measures have been developed to conserve the buttonwood mangroves. These measures include the protection of existing mangrove forests, the restoration of damaged mangrove areas, and the development of sustainable practices for mangrove resources.
Education and outreach programs can also help raise awareness about the importance of buttonwood mangroves and their threats. This will help promote the adoption of conservation measures by policymakers and local communities.
FAQs
Is Conocarpus erectus a true mangrove?
Buttonwood mangrove is not classified as a true mangrove. However, it typically grows in areas where other mangrove species grow. It grows farther inland than all the three true species of mangroves, forming excellent buffer systems.
Are buttonwood mangroves endangered?
At the moment, buttonwood mangroves are not on the endangered species list. However, coastal development, habitat destruction, pollution, and climate change threaten their long-term survival.
What makes buttonwood different from other mangrove trees?
All other mangrove trees produce flowers that develop into propagules, while buttonwood mangroves produce flowers that grow into small, round, button-like fruits. In terms of leaf arrangement, the leaves of true mangroves occur opposite each other, while the leaves of buttonwood alternate.
Is buttonwood mangrove edible?
No, buttonwood mangrove is not considered edible, especially for human consumption. While some parts of the tree are harvested in some cultures for medicinal purposes, its fruit is generally bitter, with an unpleasant taste.
