Description from Flora of China
Trees, evergreen, glabrous, columnar or spreading, not buttressed, surrounded by pencil-like pneumatophores arising from long, shallowly buried, horizontal roots. Leaves simple, opposite, borne in one plane, entire, leathery, apex often with a minute hydathode forming a thick mucro. Flowers 1-3 clustered at apex of ultimate, pendulous branchlets, actinomorphic, 4-8-merous, opening at night. Floral tube shallowly campanulate, at fruit maturity persistent, partly surrounding fruit or expanded and saucer-shaped with fruit fully exposed; sepals 4-8, adaxially green or red, thick, leathery. Petals red or white, lanceolate-linear, caducous, vestigial, or absent. Stamens numerous; filaments red or white; anthers reniform. Ovary superior to partly inferior, depressed, 10-20-carpellate. Fruit globose, berrylike, leathery, indehiscent, crowned by style base. Seeds numerous, embedded in foul-smelling pulp, irregularly angular or falcate; seed coat thickened, roughened, somewhat corky. 2n = 24.
Hybridization among species is reportedly common, although molecular studies on Chinese populations of Sonneratia ×gulngai and S. ×hainanensis concluded that these species exist only as repeatedly produced F1 hybrids. No evidence of F2 backcrossing or intercrossing among the hybrids led to the conclusion that S. ×gulngai and S. ×hainanensis should not be considered true hybrid species (see Zhou et al., Molec. Phylogen. Evol. 35: 595-601. 2005).
Nine species (including three natural hybrid species): mangrove communities from E Africa to Indo-Malesia, Australia, New Guinea, and the W Pacific islands; six species (one endemic, one introduced) in China.
(Authors: Qin Haining (覃海宁); Shirley Graham, Michael G. Gilbert)