From Common Forest Trees of Hawaii

American Mangrove
Rhizophora mangle
American Mangrove family (Rhizophoraceae)

Post-Cook introduction

This species, naturalized on protected muddy seashores, is easily recognized by the mass of peculiar branching curved and arching stilt roots that enable the trees to spread in shallow salt and brackish water and form dense, impenetrable thickets at tide level. Each supports an attached odd cigarlike seedling that elongates hanging down.

©2010 Shirley Denton
Small tree to 33 ft (10 ) high and 8 inches (0.2 ) in trunk diameter, reported to reach a height of 75 ft (23 ) elsewhere. Bark gray or gray brown, smooth and thin on small trunks, becoming furrowed and thick on larger ones. Inner bark is reddish or pinkish, with a slightly bitter and salty taste. Twigs are stout, gray or brown, hairless, ending in a conspicuous narrow pointed green bud 1–2 inches (2.5–5 ) long, covered with 2 green () around a pair of developing leaves and making a ring scar around the twig when shedding.

Leaves crowded at end of twig, hairless, with slightly flattened leaf-stalks of 1⁄2–7⁄8 inch (13–22 ). Blades elliptical, 2 1⁄2–4 inches (6–10 ) long, blunt-pointed at and short-pointed at base, slightly rolled under at edges, slightly leathery and fleshy with side veins not visible, shiny green above, yellow green beneath.

Flowers, usually 2–4, together at leaf base on forked green stalks altogether 1 1⁄2–3 inches (4–7.5 ) long, slightly fragrant, pale yellow, about 3⁄4 inch (2 ) across. The bell-shaped pale yellow base () less than 1⁄4 inch (6 ) long bears four widely spreading narrow pale yellow almost 1⁄2 inch (13 ) long, leathery and four narrow petals 3⁄8 inch (10 ) long, curved downward, whitish but turning brown, white wooly or cottony on inner side; eight and of two-celled mostly inferior but conical at with two ovules in each cell, slender and two-

are dark brown, conical, about 1 1⁄4 inches (3 ) long and 1⁄2 inch (13 ) in diameter, with enlarged curved remaining attached. The single seed germinates inside forming long narrow first root (radicle) green except for brown enlarged and pointed end, to 1⁄2 inch (13 ) in diameter. When about 8–12 inches (20–30 ) long, the heavy seedling falls into the mud or water. It may be carried by water and ocean currents before becoming firmly rooted. Flowering and fruiting continue through the year.

The sapwood is light brown, heartwood reddish brown or dark brown. The wood is hard, very heavy ( gr. 0.9–1.2), durable in the soil but susceptible to attack by dry-wood termites.

Elsewhere, it is used as roundwood for posts and poles and is excellent for fuel and charcoal. Wood in larger sizes has been employed also for marine piling and wharves, shipbuilding, and in cabinet work. The bark is important commercially in tanning leather, and the leaves are rich in tannin also. A dye and medicines have been obtained from the bark. Fishermen in Puerto Rico preserve their lines with an extract from the roots.

Mangrove forests on depositing shores aid in extending the shoreline, holding the black mud in place and gradually advancing on the side toward the ocean. Where native, this species with its stilt roots growing in shallow water extends farther seaward than mangroves of a few other plant families.

Planted and naturalized in salt marshes of Kauai, Oahu, Molokai, Lanai, and Hawaii. Trees can be seen from the bridge at Heeia, as well as the shoreline reefs of Kaneohe Bay and Leeward Molokai.

Height 61 ft (18.6 ), c.b.h. 3.7 ft (1.1 ), spread 23 ft (7.0 ). Kohana-iki, Kailua-Kona, Hawaii (1968).

Widely distributed on sift shores of the Atlantic Coast of tropical America from Florida, Bermuda, and Bahamas through West Indies and from northeastern Mexico to Brazil. The same or closely related species also on Pacific Coast from northwestern Mexico to Peru, on coasts of western Africa, and in Melanesia and Polynesia.

Other common names
red mangrove, common mangrove, American mangrove; mangle, mangle colorado (Puerto Rico, Spanish)

Rhizophora mangle var. samoensis Hochr., R. samoensis (Hochr.) Salvoza

Where necessary to distinguish other unrelated mangroves of seashores, this species is known as red mangrove.

Red mangrove was first introduced to Hawaii in 1902, according to Degener (1933-1986), to hold the soil in the mudflats of southwest Molokai. It has become thoroughly naturalized there. Twenty years later, this and other mangroves were planted in salt marshes of Oahu. Classed also as a weed, often spreading into fish ponds, where eradication is difficult (Hasselwood and Motter 1966).

An evergreen tree retains a large portion of its green leaves all year.

stamen -- the pollen-producing reproductive organ of a flower; The stamen consists of an anther supported by a filament.

style -- This is a long and thread-like structure that connects the stigma with the ovary. A flower may have a single style, or several of them.

scale -- A very small leaf around a dormant bud. Also other things that might remind one of fish scales on the surface of ferns, stems and the like.

synonym -- In botany a synonym is a species name that at one time was thought to be the correct name for a plant but was later found to be incorrect and has been replaced by a new name.

cm -- A centimeter which is about 0.4 inches.

In an opposite leaf arrangement the leaves come in pairs with one leaf on each side of a stem.

mm -- millimeter. About 1/25th of an inch.

The hypanthium or floral cup is a cup-like structure formed by the fused bases of the stamens, petals, and sepals.

persistent -- When the leaves of a plant fail to fall off in the fall they are persistent. Flowers that stay around after fruiting would be persistent.

m -- A meter is about 10% larger than a yard.

A pistil is the female structure of many flowers. It contains one or more carpels. Each carpel contins an ovary, style and stigma. The stigma receives the pollen which grows thru the style to reach the ovary.

The apex is the tip or the furthest point from the attachment.

fruit -- any seed-bearing structure in flowering plants. It is formed from the ovary after flowering.

stipule -- A leaf-like structure that occurs where the leaf joins the stem; stipules often occur in pairs.

lobe -- Rounded parts of a leaf (or other organ). Lobes bulge out about 1/4 of the leaf diameter.

stigma - The tip of a pistil that receives the pollen.

An ovary is a part of the female reproductive organ of the flower. Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary.

Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom.

sp. -- The abbreviation for "species". The plural is "spp". When used it sometimes means that the exact species is unknown. For example, "Aster sp" would mean some species within the Aster genus but the writer may not know exactly which species.