In July 2009, an orchard owned by Asroful Uswatun, Jember, was full of visitors. It was the first yellow dragon fruit Selenicereus megalanthus harvest time in the orchard situated at the altitude of 17 m above sea level (asl). There were 150 plants of 2 years old fixed on 50 poles. On each pole there are 70 - 140 ripe fruits. Every week, 5 - 10 quintal of fruit can be harvested from that population. It weighs averagely 140 g each.
1,5 years earlier, David Kristanto has tried to grow yellow dragon fruit on lowland. He potted some yellow dragon fruit plants at his residence in Surabaya, located at the altitude of 10 m asl. He realized that yellow dragon fruit also bears fruit frequently on lowland though it generates smaller fruit (weighing 125-150 g each) than the fruit grown on highland (weighing 200-250 g each). Smaller fruit size is assumed to be caused by the shorter time required by yellow dragon fruit to attain ripeness. Based on David's experience, yellow dragon fruit on lowland takes 65 days from the flower first emerged to the fruit ripened, while yellow dragon fruit on highland needs 80 days. Sobir PhD of Center for Tropical Fruit Studies (Pusat Kajian Buah Tropika, PKBT) explained that on lowland the air temperature tends to be higher so that the total heat unit (heat energy required by plants for the process of fruit physiological development and maturation) is fulfilled faster than on highland even before the fruit reaching its maximum size. Moreover, the high temperature at night also increases respiration rate so that most of the output of photosynthesis is used for respiration. It is such process that makes the fruit size of yellow dragon fruit on lowland unoptimum.
Albeit the size, the fact that dragon fruit bears fruit rapidly on lowland is breaking the assumption that yellow dragon fruit is only adaptive on highland. Many literatures recorded that the original habitat of yellow dragon fruit is on highland at the altitude of approximately 700 m asl in Mexico. It is unlike any other dragon fruits that are indigenous to dessert area.
The discovery of yellow dragon fruit fruiting densely in Jember and Surabaya becomes an evidence that just as other variants of dragon fruit, yellow dragon fruit also prefers full sunlight exposure and that altitude difference (0 - 700 m asl) is not a problem. ‘But if it is cultivated on highland with full intensity and high humidity, an optimum fruit size surely can be attained,’ stated Sinatra Harjadinata, a dragon fruit farmer in Bogor. In the future, who knows there will be more yellow dragon fruit grown on lowland. (Nesia Artdiyasa)