Flowering and fruiting phenology of jackfruit (Artocarpus heterophyllus Lam.) from Sumatra landraces in ex situ conservation area in Karangmojo, Yogyakarta

This study aimed to determine the flowering and fruiting phenology of jackfruit originated from Sumatra landraces planted in ex situ conservation in Yogyakarta within the 2018 and 2019 flowering periods. Flowering ontogeny and phenology were observed following Owens and Pushpakumara methods. Results found five developmental stages of male inflorescences, which last in 64-101 days, ended by the drought and abscissed of the males. Female inflorescences undergo five stages which take 92-160 days in total. Differences in rainfall and the dry season period resulted in different onset and duration of flowering. In 2018, which has more rainfall and a shorter dry season, flowering initiates lately (February-June) with a longer duration (6 months). In 2019, the less rainfall and more extended dry season resulted in early flowering (January-April) with a shorter duration (4 months). The Medan landrace flowered later and longer. Flowering synchrony occurred between sexes within the same tree, but there was asynchronous flowering among individual trees. Water availability is crucial in flowering and fruit production. Flowering stimulation and pollination management may also be conducted to increase flower production, pollinating agents, and fruit production and synchronize the flowering.