Rhizophora mangle or American Mangrove is a deciduous tree native to tidal shores, marshes and estuaries of America and Tropical America. It occurs as dense forests on many of these coasts and is an important tree for it soil holding capacity. As the tree grows, it forms arching aerial roots that help make thick tangles that stabilize soil. Leaves are leathery, dark green, opposite and petioled. The leaves are obovate to elliptic to 6 inches (15 cm) long. In nature, the trees will reach 40 ft (12.19 m) in height with a thick canopy. The gray-brown bark is an important source of tannins. Most mangroves live in brackish water, but they can also live in fresh water. This mangrove will even grow in an aquarium if planted there. Their size is easily controlled by container size. Our specimen is only 12 ft (3.65 m) tall at over 25 years old. Actually they are relatively easy to grow. Trees are hardy in USDA zones 11.
Blooming: Terminal flowers are about 1 inch (2.5 cm) across, green, villous and not particularly showy. Flowers give way to viviparous seeds called propagules that germinate on the plant to form large dagger-like seedlings that will stab into the mud to establish a new plant when they drop. Propagules form leaves and have fully mature organs before dropping from the parent tree.
Culture: Rhizophora mangle needs full sun to partial shade, with a moist to wet soil mix. We started ours in a soil mix consisting of equal parts of clay loam and sand. Once the propagules were placed in a container and grew their first new leaves, they were placed in large tanks of fresh water. As the plants, grew more water was added until prop roots started forming when the plants were about 2 ft (60 cm) tall. At this point, we stared fertilizing the plants once a month with a water soluble fertilizer. They grow very fast. Currently, we let the water evaporate and add new water on a monthly basis. Since the plants are native to Tropical America we do not let the temperature fall too low in winter.
Propagation: Rhizophora mangle is easily propagated by planting new propagules after they form seed after flowering.
Rhizophora mangle was featured as Plant of the Week December 4-10, 2009.
Guide to Past Plants-of-the-Week:
Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.