Tumu is the most widely distributed of the Rhizophoreae family.
The kneed pneumatophores comprise a sponge-like system of air
chambers and tubes which acts as an air reservoir when the roots are
submerged. The pneumatophores are covered with many lenticels which
allow air but not water to enter the root.
Uses as food: Leaves and peeled seedlings are soaked, boiled and
eaten. Seedlings are the staple of some in Papua New Guinea, but
eaten only in times of famine in Moluccas. Seedlings may be added to
betel nut as an astringent. Seedlings are also made into a
sweetmeat: they are sliced, soaked to leach out the tannins, then
ground into a paste. The bark may be used to flavour fish.
Other uses: The timber is heavy and tough, but has straight fibres
and a fine grain. This makes it hard to work with, but valuable as
fishing stakes, pilings, telephone poles, railway sleepers, heavy
pillars and beams, and other construction. It is commercially
planted in Indonesia, Sabah and Sarawak to produce wood chips that
is turned into paper pulp or to produce rayon fabric. It is also
favoured as firewood and for conversion into charcoal as it produces
the most heat among mangrove woods.
Traditional medicinal uses: The bark is astringent and used to treat
malaria (Cambodia), cure fish poisoning (Marshall Islands), treat
diarrhoea and fever (Indonesia). Elsewhere the fruit is used to
treat eye problems, and scrapped skin of the fruit to stop bleeding.
The fruit may also be chewed as a betel nut substitute. The leaves
are used to control blood pressure (India).