Watering bonsai can be the most difficult part of the bonsai process. While failing to water your bonsai can certainly kill it, overwatering can have the same drastic effect. Identifying the irrigation balance requires patience and attention to the bonsai's individual needs.
Check the soil moisture of your bonsai plant daily. Stick your finger 1 to 2 inches into the soil to feel for moisture levels. Pay attention to the color of the compost as it changes slightly with the moisture levels. Use the finger test until you are comfortable monitoring the color. Check the moisture levels several times a day during the summer months--the bonsai may demand more irrigation during this period.
Irrigate your bonsai plant when the moisture levels feels somewhat dry but do not allow the bonsai's soil to dry out completely. Irrigate the bonsai at soil level to prevent wetting the foliage, which increases the potential of fungal diseases.
Water your bonsai in the early morning so that it will have the entire day to process nutrients. Irrigate again in the late evening, only if the bonsai requires it. Avoid irrigating during the height of the sun; this water is generally evaporated and never reaches the roots.
Water all corners to ensure that the entire container receives equal amounts of water. Irrigate the bonsai deeply until the water flows evenly from the container's drainage system. Remove the water immediately from any catch trays to reduce disease potential.
Maintain a consistent environment for the bonsai based on its individual needs. For instance, maintain a moist but not saturated environment for lily bonsai while allowing pine bonsai to dry slightly between each irrigation.