A small to moderately sized, evergreen tree that is capable of growing to 35 m tall but most of the trees found in the Maldives are 6 to 10 m in height. It is a single-stemmed tree with short buttresses and characteristic knee-shaped above-ground breathing roots. Bark is pale grey or brown, thick, hard and rough. Leaves are simple, opposite in arrangement, leathery, dark green in colour, 8 to 22 cm long and 5 to 8 cm wide with 2 to 5 cm long leaf stalk. Flowers are single and axillary in position. Calyx is reddish to scarlet in colour with ten to 14 pointed lobes, which are smooth or with grooves above lobe junctures. Petals are orange-brown in matured flowers, bilobed and each lobe has three to four long bristles. Viviparous propagules are cigar shaped, 15 to 25 cm in length, 1.5 to 2 cm in diameter, stocky with blunt narrowed apex. Propagules detach with calyx, buoyant and dispersed by currents.
Occurrence in Maldives: It is found growing as a dominant or co-dominant species in many of the mangrove ecosystem of the Maldives. This species often occurs with the Tall-stilted Mangrove (Rhizophora apiculata, Thakafathi) in areas that receive some freshwater. In the Maldives it is found in Hoededhoo (Gaaf Dhaal), Filladhoo (Haa Alif), Gan (Laamu), Huraa (Kaafu).
The name gymnorhiza comes from two Greek words "gymno" naked and "rhiza" root, naked root which refers to the exposed knee roots of Bruguiera gymnorhiza emerging from the ground.
The main difference from other Bruguiera species is that Bruguiera gymnorhiza has the largest leaves, flowers, propagules and lenticels of all Bruguiera species.
The name Large-Leafed Orange Mangrove comes from the orange flowers and the large leaves that can reach up to 25cm in length.
Bruguiera gymnorhiza was described for the first time in 1798 by avigny ex Lam. & Poiret.
It is capable of growing well in somewhat dry and well-aerated soil in the mid- and high- tidal areas of the intertidal zone. It tolerates up to 50 ppt of soil salinity but optimal salinity range is reported to be between 8 and 26 ppt. It is one of the most shade tolerant mangrove species and seedlings may grow under a full forest canopy. It is propagated by propagules. Matured propagules are reddish-brown or greenish-red in colour. Fresh and healthy propagules can be collected from the mother trees or freshly fallen propagules without any damage can be used for planting. Propagules can be stored for about a week by keeping the lower portion in brackish water or by wrapping them with wet jute bags. Propagules can be directly planted in selected fields by inserting them up to one–third of their length. Nursery-raised seedlings about 35 cm in height can be used for outplanting. Direct planting is most successful and economical.
Mangroves in general are under threat from coastal development, and this species, which grows on the landward edge of the mangrove area, may be more threatened by rising sea levels than are other species because it may be unable to move further inland. There may be a decline in populations of this species due to habitat loss or harvesting, but it is a common species of mangrove with a very wide range, and is not declining at a sufficient rate to be included in any threatened category, so it is listed by the International Union for Conservation of Nature as being of "least concern".
The wood of Bruguiera gymnorhiza has very high density and therefore very heavy wood which made it very attractive as timber for the use of saltwater and foundation pilings, house posts, flooring, cabinetwork and furniture.
Bruguiera gymnorhiza was also used as source of dyes for fishnets, ropes, sails and clothing.
Powdered bark was used for the preparation of tuba, a very popular, alcoholic drink in the Philippines made from coconut sap.
Nowadays charcoal and firewood is made of Bruguiera gymnorhiza in the Philippines while the knee roots are utilized in planting rituals so cultivated tubers will grow big.
Tiwi people use the timber of Bruguiera gymnorhiza to make throwing sticks for hunting magpie gees.
Macassar, the biggest port in the south of Indonesia was the main trade center for sea cucumbers in the 18th century. The sea cucumbers have been catched on surrounding small islands and been shipped to China, in that time the most important export product of Macassar to China. People produced a red dye of Bruguiera gymnorhiza which was used to treat trepang.
In the Maldives, propagules are consumed regularly during the fruiting season. They are peeled, soaked and boiled three or four times in water and eaten. Sometimes they are cooked with salt, dried and then consumed. Though the timber is hard and tough it is not widely used because it easily decays. Bark is used for tanning fishing nets.