Vitex Trifolia L. is a Chinese herb known for treating wind-heat, especially if accompanied by pain on the vertex of the head. The Chinese use the seeds, which they call Man Jing Zi. In Bali, Indonesia, it is called Legundi.
In Bali, the locals use it for another reason, to bring down cases of dengue. Dengue is passed around by the Aedes mosquito, which breeds in stagnant waters and comes out only during the day to suck on your blood. Unfortunately, some of these Aedes mosquitoes are infected with the dengue virus and may pass it on to you. One way to reduce the chances of being infected is to not leave stagnant water lying around the house, e.g. water in plant pots, in buckets or even in the water tank. Ponds with fish in them are fine, as the fish would happily lap up on the mosquito larvae.
Another way to keep these mosquitoes out of sight is burn the crushed leaves of Legundi. However, because the leaves are naturally insecticidal, the mere planting of them around the house is sufficient to keep the mosquitoes away.
In addition to being insecticidal, the leaves are also antimicrobial, analgesic, antiinflammatory and antipyretic, which explain the Chinese use of its fruit, which will contain similar components – mainly the alkaloids.
Vitex Trifolia L. (also known as Simpleleaf Vitex) is often confused with Vitex Agnus Castus (also known as Vitex Chasteberry) from the the European tradition. While both are fruits of the Vitex genus, their functions are slightly different. In addition to having properties similar to that of the leaves, the fruit is also a known emmenagogue.