In anticipating the rapid decrease of energy resource, especially fossil fuel, immediate actions are required to fulfill the needs of highly-increased population in the world. Innovation to produce renewable energy from easily-utilized raw materials should meet society’s needs including renewable raw materials from wood biomass for energy.  Genetically-improved kaliandra (Calliandra calothyrsus) has been developed for this purpose. Due to low success rate of its reproduction, study on its reproductive biology was undertaken. The study was carried out during the flowering seasons of C. calothyrsus, by examining flower morphology, pollen and pistil viabilities as wee as insect visitors to this species’ flowers.

The study showed that the flowers of C. callothyrsus are borne on inflorescences (spikes) and carrying an average of 354 individual flowers, which develop acropetally. Pistils (female organ) cease to develop by the 2^nd to 3^rd day after their appearance, and the flowering is becoming ceased then.  Pistils showed maturity during the periode of 09.00 WIB - 10.00 WIB and pollen is still viable from 1 to 3 days after the pollen opening. Three most frequent visitors (families: Apidae, Vespidae, Formicidae) and one order lepidoptera were found visiting C. calothyrsus flowers However, the reproductive success of C. callotyrsus is found to be very low, which is only 0.0086. These preliminary results confirmed that the low reproductive success of C. callothyrsus is due to the structure and development of flowers allowing the incidences of both outcrossing and self-pollination. The limitation time of pistil maturity might also contribute to the low reproductive success of this species.