The status of the stored food reserves within the tree influences the flowering and fruiting pattern in rambutan. Most, but not all, flowers open early in the day. Up to 100 flowers in each female panicle may be open each day during peak bloom. Initial fruit set may approach 25 percent but a high level of abortion contributes to a much lower level of production at harvest (1-3%). The fruit matures 15 to 18 weeks after flowering.
Both male and female flowers are faintly sweet scented and have functional nectaries at the ovary base. Female flowers produce 2-3 times more nectar than male flowers. Nectar sugar concentration ranges between 18 and 47 percent and is similar between the flower types.
Cross-pollination is necessary because there is no pollen in most functionally female flowers. rambutan, like lychee, is dependent upon insects for pollination. Aromatic rambutan flowers are highly attractive to many insects, especially bees. Those commonly found visiting rambutan flowers include bees, butterflies and flies. Apis cerana (honey bee) colonies foraging on rambutan flowers produce large quantities of honey. Bees foraging for nectar routinely contact the stigmata of female flowers and gather significant quantities of the sticky pollen from male blossoms. Although male flowers open at 0600 h, foraging by honey bees is most intense between 0800 and 1100 h, tapering off rather abruptly thereafter. In Thailand, A. cerana is the preferred species for small scale pollination of rambutan.
Placing honey bee colonies in rambutan plantations is an important and practical recommendation for assuring adequate pollination and fruiting. The bees should be present continuously throughout bloom. Although no specific number of colonies per unit of rambutan can be recommended, strong colonies should be provided at a minimal rate of one per acre (0.4 ha). |
