Applying water to bonsai trees is a difficult technique and it might take you a long time to get the point. Some beginners are always afraid that their bonsai plants do not have adequate water and they are very likely to apply too much water to the plants. Over-watering also will weaken the health of the bonsai plant and it is not easy to discover as well. Unlike the normal trees growing in the garden, the roots of the bonsai tree do not have a large space to spread if they need more water. You should keep an eye on your potting compost to judge if you need to apply more water to the container.
During the daily watering for your plants, you can gradually accumulate some experience on how to water the bonsai trees with the correct amount of water and in the correct time. It is said that in Japan it will take a gardener three years to learn watering bonsai trees. Before applying water to the compost, you need to do a thorough observation before applying any water to the pot. Watering on a daily basis is not a good idea without observing the conditions of compost. You should decide if you need to water more than once in a day. In hot summer days, another time of watering might be required to keep the moisture. Generally, the best time to water bonsai trees is when the surface of the potting compost has become dry. You can gain adequate experience during the daily observation.
When apply water to the bonsai, you need to do a thorough watering instead of put some slight moisture on the compost. A thorough watering means the plant should be fully soaked in the water for a while and the water should be seen following out of the draining hole of the pot. According to the Japanese adage for watering the bonsai trees, they need to be watered twice with an interval of about 20 to 30 minutes. The first time is used to make the dry soil to accept water and the second time will deepen this process. Once the water can be seen from the bottom hole of the container, the process is considered as successful.
Image provided By Peggy Greb, USDA [Public domain], via Wikimedia Commons