Sensitive Plant (Neptunia aquatica) is another floating plant that gets a tiny yellow flower on it. Its foliage contracts at the slightest touch. The flowers are yellow tufts that are about 1 inch wide and bloom throughout the summer on its running stems. It does great just floating in your pond or you can plant it in soil at the edge of your pond where it can reach 6 inches tall. Does good in part shade and full sun. Its considered to be a hardy plant for zones 9-11.