The method whereby a bonsai pot is dipped into a water-filled basin to allow it to absorb water from the bottom of the pot. It is also called koshimizu kansui (water-filled basin for watering). It is effective in preventing the bonsai pot from suffering a dearth of water in the summer. Some trees particularly need plenty of water and yanagi (weeping willows) get koshimizu from late May to mid-September. A kind of koshimizu is applied to a plant with its roots extending to the extremities of the pot so that it is able to receive a sufficient amount of water.
translated by Kyodo News