Papaya is a fast-growing, semi-woody tropical herb. The stem is single, straight and hollow and contains prominent leaf scars. Papaya exhibits strong apical dominance rarely branching unless the apical meristem is removed, or damaged. Palmately-lobed leaves, usually large, are arranged spirally and clustered at the crown, although some differences in the structure and arrangement of leaves have been reported with Malaysian cultivars (Chan and Theo 2000). Generally, papaya cultivars are differentiated by the number of
leaf main veins, the number of lobes at the leaf margins, leaf shape, stomata type, and wax structures on the leaf surface, as well as the color of the leaf petiole. Papaya grows best in a well drained, well aerated and rich organic matter soil, pH 5.5-6.7 (Morton 1987). Waterlogging of soils often results in the death of trees within 3-4 days (Storey 1985). The plants are frost-sensitive and can only be grown between latitudes 32′ N and S (Litz 1984), with optimal growth at 22-26°C and an evenly distributed rainfall of 100-150 cm.