Kang kung is usually planted by the stem's nodes which in time grows roots. But did you know, it can produce seeds as well? If you let kang kung mature, it will grow flowers, which in turn will form seed pods, which then produces roughly 3-4 seeds ready to be planted.
Kang kung seeds are fairly easy to harvest. First you let the kang kong plant grow 2-3 months and let it flower. Once the flower is fertilized, it will form seed pods. Once the seed pods turns white -- it is ready to be harvested. You can pull it apart and you should find 4 seeds in the pod. Those 4 seeds can then be stored and planted for future use.