In 2012, there were about 24,573 ha of durian in Viet Nam, distributed mainly in three regions, Highland, the South-east and the Mekong delta (MD); the area of the latter made up almost 50% of that of the whole country. In recent years, the most popular durian cultivars cultivated in the MD are 'RI 6', 'Monthong' and 'Kho qua xanh'. Durian starts to flower naturally in December-January, and is harvested from May to June as an effect of drought conditions; however, in the MD, durian can be induced to flower year-round thanks to good irrigation-drainage systems. Growers induce durian flowering by applying a combination of treatments including plastic mulching of the raised beds, ditch drainage within 30-40 days, and foliar spray of paclobutrazol (PBZ) at 1000 and 1500 ppm when the leaves turn from light to dark green (2-3 months old). The period of emergence of inflorescence buds and the flowering ratio vary depending on cultivar, climate, and the extent of drought conditions. 'Kho qua xanh' is easier to induce to flower than 'Sua hat lep', 'RI 6' or 'Monthong'. 'Kho qua xanh' starts to flower concentratedly from 20-25 days after induction whereas, for the other cultivars, flowers appear from 30-35 days after induction or longer, and there may be two or three periods of flowering if there are heavy rains and the ditches are not drained completely.