The Commelina communis L. is one kind of annual weed The seedlings emerge from middle of May.The emergence period of seedling are last to days.The flowers bloom in middle of June and mature seed fall off during september.The most seeds are distributed in 0～25 cm soil, 9～18 grains per squaremeter.The optimum depth of soil and temper of seed emtrgence are 2～6 cm and 10～15 ℃ respectively The herbicide tests shown that 74 2%～90% of Commelina communis L. plants can be controlled by spraying of 2.0～2.5 kg/hm² zuodan water at 4-leaf stage.