July 2016. Can anyone tell me what this plant is? We found it today during a roadside survey, and would like to know if we should be concerned about it. The plant is about 1 m tall, but looks like it could grow taller. The stem is woody, about 0.5 cm in diameter. There were no fruits yet; just flowers.
This legume plant looks like a single alfalfa or lucerne (Medicago sativa) plant, a forage plant, a subspecies or a close relative.
Another member suggested that it was Millettia pinnata. But as pointed out by another person, Millettia pinnata is a big tree formerly known as Derris indica or Pongamia pinnata. It can grow up to 15-25 m. Its common name is Indian beech tree or Indian biodiesel tree. Its use is similar to that of jatropha or the physic nut. It is also considered an invasive species in Australia, although its distribution includes PNG and Australia in the literature. In the pictures Palau sent, the plant has a compound leaf with three leaves so its not likely to be a tree.
Millettia pinnata is commonly called Pongamia – a multfunctional oil seed tree. Does not flower until about its 4th year, so it is by then perhaps <2 m tall. Leaves have 7 or 9 leaflets, each 2-3 cm across. less compact flower head (see attachment below). Alfalfa/lucerne has trifoliate compound leaves – some in the photos conform to that, others do not.