Medium-sized tropical tree introduced throughout most of the tropics for its edible fruit and firewood. This shade tolerant species produces monotypic stands, but is a poor disperser. Although it displaces most native flora, it favours a limited number of endemic species.
Evergreen tree up to 12 m high and stem diameter in excess of 60 cm. Crown diameter of mature trees usually far exceeds tree height. Lifespan unknown but probably over 100 years.
No cultivars have been recognized but the species is often considered to be rather variable. It is tolerant of a wide range of environmental conditions.
The whitish scented flowers are large with numerous showy stamens (10-50 mm long). The sub-globose fruit (up to 4 cm long) is a yellowish berry consisting of a fleshy pericarp enclosing a large seed (ca 2 cm in diam.). The seeds are polyembryonic and produce up to eight seedlings each. Flushes of growth are largely synchronous. Flowering occurs in Spring in the sub-tropics or at the end of a dry period. The fruits ripen in about three months. Saplings 1 m tall are able to flower under the canopy of their own kind. Trees may start to bear from the age of four but never yield large fruit crops.
Trees may occasionally layer. It is highly wind resistant and salt tolerant.
This species is highly shade tolerant and may become established under deep shade. In its native it is unlikely to be a component of the forest canopy due to its low stature.
In former times its fruit was sought after to be eaten raw or made into preserves or jellies. As this rather insipid fruit is easily bruised and highly perishable it has gone out favour and is usually consumed only by children. Bark, roots, fruits and seeds have been used in home medicine, however large applications may be poisonous. Tannin and a brown dye can be extracted from the bark. The species has been extensively used as a excellent source of firewood, and for amenity, windbreak and erosion control purposes. The timber is of poor quality but is used for general turnery. When distilled the fruits yields an excellent rosewater.
The species native range is thought to be in the East Indies and Malaya. Because of its former importance as a food source its range and abundance in SE Asia was greatly affected in prehistoric times.
Humid tropics.
The original habitats and site requirements are unknown.
Not reported.
It has no noticeable insect enemies but the leaves are often coated with mould growing on honeydew.
During the 18th century S. jambos was introduced to tropical botanic gardens generally located on islands (e.g. Jamaica, Mauritius). Throughout the 19th century the tree was introduced to more remote oceanic islands such as Pitcairn.
S. jambos invades all forest types including natural forests. It is a poor disperser and in most instances seeds are locally dispersed by gravity and probably also by rats (uphill). New foci of invasion are caused by humans (especially children discarding seeds after eating the fruits) and, when present, by fruit bats. Evidence from Pitcairn Island suggest that the species starts to regenerate as soon as fruits are produced and that the rate of spread is no more than one meter per year. However once established it forms monotypic stands often consisting of three distinct layers (canopy, sapling and seedlings).
On tropical islands it grows from sea level up to 900-1200 m. In Ecuador it even reaches an altitude of 2,300 m. At its upper limits the tree grows vigorously but fails to bear fruit. It tolerates a wide range of soils, temperature and rainfall. It withstands minimum temperatures down to 0ºC.
All subtropical oceanic islands with moist forests may be invaded by S. jambos. In more arid areas the species is restricted to water courses.
As in the native range the species has few insect enemies and the leaves are often coated with mould growing on honeydew. On Pitcairn Islands fruits are readily attacked by introduced fruit flies. The species does not appear to be favoured by large herbivores.
The main observed impact of S. jambos is the displacement of most native species on Oceanic islands where the species reaches canopy height. However, when S. jambos grows in areas affected by a large number of invasives, and Lantana camara especially, the species provides a safe heaven for some of the native species (e.g. endemic bird on Pitcairn, epiphytes in S. America). Stands of mature trees provide the right regeneration micro-habitats for some native species but unless the species is shade tolerant they will fail to grow to maturity. Mature stands of S. jambos result in soil erosion and gully formation.
The dense and extensive root mat produces by mature trees is detrimental to shifting agriculture or in agroforestry systems. The open ground and shrub layers of S. jambos stands favour access to humans. The species has some value for bee-keepers.
When cut S. jambos resprouts profusely to produce impenetrable thickets. Control can be achieved if herbicide is applied on stump or the stump is pulled out of the ground. Prior to cutting any seedling and/or sapling bank must be eliminated.
On most tropical islands the majority of tree species require some degree of light for regeneration whereas S. jambos is shade-tolerant and will become freely established under complete tree canopy including its own.
Due to the unclear nature of the native range no clear differences can be identified. However, it is possible to surmise that in its native range S. jambos does not reach canopy height, unlike on most tropical islands it invades, and thus remains a subcanopy species.
- * Binggeli, P. & Starmer, J. (1997) Pitcairn Island. Aliens 6, 2.
- * Figier, J. & Soulères, O. (1991) Le problème des exotiques envahissantes à la Réunion. Bois For. Trop. 229, 31-34.
- * Fleischmann, K. (1997) Invasion of alien woody plants on the islands of Mahé and Silhouette, Seychelles. J. Veg. Sci. 8, 5-12.
- ## Morton, J.F. (1987) Fruits of warm climates. Published by the Author, Miami.
- * Strahm, W. (1989) Plant red data book for Rodrigues. Koeltz Scientific Books, Konigstein.
- # Weaver, P.L. & Nieves, L.O. (1978) Periodic annual increment in a subtropical moist forest by Syzygium jambos (L.) Alston. Turrialba 28, 253-256.
Pierre Binggeli
December 1999