Syzygium samarangense (Blume) Merr. & Perry

Tree, 5-15 m tall, with short and crooked trunk, 25-50 cm diameter, often branched near the base and with wide, irregular canopy. Leaves opposite, elliptic to elliptic-oblong, 10-25 cm x 5-12 cm, coriaceous with thin margin, pellucid dotted, rather strongly aromatic when bruised; petiole thick, 3-5 mm long. Inflorescences terminal and in axils of fallen leaves, 3-30-flowered; flowers 3-4 cm in diameter, calyx-tube ca. 1.5 cm long, ventricose at apex, lobes 3-5 mm long; petals 4, orbicular to spathulate, 10-15 mm long, yellow-white; stamens numerous, up to 3 cm long; style up to 3 cm long. Fruit a berry, broadly pyriform, crowned by the fleshy calyx with incurved lobes, 3.5-5.5 cm x 4.5-5.5 cm, light red to white; flesh white spongy, juicy, aromatic, sweet-sour in taste. Seeds 0-2, mostly suppressed, globose, up to 8 mm in diameter.

There are definite flowering seasons, often two, sometimes three in a year, but the timing varies from year to year. Wax jambu commonly flower early or late in the dry season; the flowers appear to be self-compatible and the fruit ripens 30-40 days after anthesis.

The trees prefer heavy soils and easy access to water instead of having to search for water in light deep soils.

The trees are at home in fairly moist tropical lowlands up to 1200 m elevation. Wax jambu grows best in areas with a fairly long dry season. This does not mean that this species is drought-resistant. The species require a reliable water supply and are often planted along streams or ponds.

The trees of S. samarangense are cultivated in home gardens, often planted along driveways and paths.

Propagation from seed is common. Seeds are sometimes abortive, and some wax jambus tend to be seedless. Seeds lose their viability quickly and should be sown fresh from the fruit. Clonal propagation through air layers, cuttings or budding is not difficult. Air layering is commonly employed in South-East Asia. The modified Forkert method is recommended for budding. Seedlings of the same or other Syzygium species are used as rootstocks. In Java 'jambu klampok' or 'kopo' (S. pycnanthum Merr. & Perry, syn. Eugenia densiflora (Blume) Duthie) is recommended as rootstock because it is hardy and not attacked by termites.

Tree spacing ranges from 8-10 m. The trees receive little attention after the first year or two when manuring, weeding, mulching and watering ensure rapid increase of tree volume. Trees which bear well benefit from compound fertilizers applied after harvest and supplemented with a top dressing as soon as the inflorescences are being formed. There appears to be no experience with pruning or fruit thinning.

There are no specific recommendations for crop protection, but the incidence of pests and diseases certainly warrants a study of the causal organisms and their control.

Food: The tree is grown for their fruit, which substitute for one another in the marketplace. It is not easy to distinguish between the various S. aqueum and S. samarangense fruits. The ripe fruit is sweet and is mainly eaten fresh. In Indonesia wax jambu is used in fruit salads ('rujak') and they are also preserved by pickling ('asinan'). Medicine: Various parts of the tree are used in traditional medicine, and some have in fact been shown to possess antibiotic activity. Timber: The wood is reddish, hard and grows to dimensions large enough for construction purposes.