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Koshimizu is a method of watering bonsai by dipping the pot into a water-filled basin. It is also called koshimizu kansui. It is effective in preventing the bonsai pot from suffering a dearth of water in the summer. Some trees particularly need this method, such as azaleas, maples, and junipers. Koshimizu helps to keep the soil moist and prevent the roots from drying out. It also washes away excess fertilizer and salt from the soil. Koshimizu should be done in the morning or evening, when the temperature is cooler. The pot should be submerged until bubbles stop rising from the soil, and then lifted and drained well.

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