In the wild, red mangroves may mature into low, bushy, round-topped trees growing up to 30 feet in height with many aerial roots, or trees up to 80 feet in height with a straight trunk and a narrow top or head.

The red mangrove is primarily self-pollinated. Germination takes place while the embryo is still attached to the parent tree. The flowers of red mangrove trees are pale yellow with four petals, about an inch in diameter, in a cluster of two or three. The fruit is a brown, leather-like berry, about an inch long. Out of the end of the fruit hangs a seed which germinates while still attached. These long, spear-shaped seeds are called propagules. They may grow in place for up to three years, reaching lengths of up to 36" before breaking off from the fruit and falling into the water.

These seedlings travel in an unusual way. In salt water they lie horizontally and move quickly. On reaching fresher (brackish) water they turn vertically, making it easier for them to lodge in mud. These floating seedlings can survive, in a state of suspended animation, for up to a year in the water. Once lodged in mud they produce roots and begin to sprout.

After sprouting, the first years of growth involve additions to the foliage without any major change in height. Prop roots appear by the third or fourth year of growth, serving as anchoring and breathing organs. These seedlings and saplings have a very low survival rate thanks to the stresses of salinity, flooding, insufficient light and pollution.

Prop roots become silt roots when they take on the function of flying buttresses. When the tree is older, the bottom of the trunk becomes an upside-down cone shape and may even loose contact with the ground. Prop roots and drop roots improve the stability of the tree by providing a broader base and support in soft mud. Ultrafilters in prop roots exclude salt while extracting water. Above-ground drop roots transport oxygen from the atmosphere to the root system.

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