Description:

This plant can be a shrub or small tree (in the northern part of Vietnam) or a large tree (in the south), reaching a height of 25-30 meters with a diameter of 60-70 cm. The bark is gray, 2.5 cm thick, and longitudinally fissured. The base has numerous stilt roots, 1-2 meters high. Leaves are simple, opposite; the leaf blade is ovate-elliptic or lanceolate, 10-16 cm long and 3-6 cm wide, with an acute base and apex, thick, shiny, and with numerous small black dots on the underside. The midrib is reddish-brown, while secondary veins are faint. The petiole is 1.5-3 cm long and pale red.

The stipules are 4-8 cm long, pink or pale red. Cymes have 2 flowers, with a pedicel of 0.5-1 cm long, arising from the axils of fallen leaves. The bracteoles form a cup-like structure at the base of the flowers. Flowers are sessile, with a fused calyx divided into 4 lobes, 1-14 cm long and 6-8 mm wide. The corolla has 4 thin, lanceolate petals, 8-11 mm long and 1.5-5 mm wide. There are 8-12 stamens. The ovary is semi-inferior, with 2 locules; the style has 2 lobes. The fruit is obovoid, 2-2.5 cm long, brown, and rough. The propagule is cylindrical, 20-35 cm long, swollen at the base, and green, turning pink when ripe.

Biology:

Flowering occurs from April to May, sometimes year-round; fruits ripen in November. Seeds germinate into seedlings on the mother tree; when mature, a collar of 0.8-12 cm long appears between the fruit and the propagule. Seedlings fall from the tree between July and September.

Habitat and Ecology:

The plant grows in mangrove forests in river estuaries, along the coast, in areas with moderate tides and compacted clay soils. It is salt-tolerant and thrives in intertidal mudflats. It often dominates or exists as a near monoculture in mangrove forests, with a thick, fertile soil, and is frequently affected by tides and sedimentation. It regenerates vigorously under pioneer trees such as Avicennia officinalis and Avicennia alba. Initially, it grows mixed with other species before becoming dominant.

Distribution:

Vietnam: Bà Rịa – Vũng Tàu (Vũng Tàu – Côn Đảo), Kiên Giang (Hà Tiên, Phú Quốc), the Mekong Delta, the Cà Mau Peninsula, and from the South Central Coast to Hà Tiên, mainly in Southern Vietnam.

Worldwide: China, India, Sri Lanka, Myanmar, Thailand, Cambodia, Malaysia, Singapore, Indonesia, Philippines, New Guinea, Australia.

Value:

The wood is hard and quite durable, suitable for construction, furniture making, and supports in mines. The resulting charcoal is low-smoke and high-caloric. The bark contains tannins used for dyeing fishing nets and tanning leather. The leaves are used as green manure, and the flowers are used for beekeeping. This plant is a main component of mangrove forests and plays a role in wave and wind protection, safeguarding coastal areas. It is a breeding ground and food source for valuable seafood species.

Conservation Status:

Endangered. Due to unsustainable and unplanned exploitation, deforestation for shrimp ponds, and other agricultural uses, the forest area and the plant’s reserves have declined rapidly and significantly. Threat level: Vulnerable.

Proposed Conservation Measures:

Implement sustainable harvesting plans and prevent indiscriminate deforestation. Clear planning and protection of raw materials are necessary.