Watering

Unlike a houseplant, bonsai trees use a "free draining" type of soil because their roots cannot tolerate "wet feet". In addition, they are grown in significantly less soil and, therefore require more watering. Factors such as tree location, temperature, lighting conditions, quantity of soil used, and the changing seasons will determine the frequency of watering. You can get to know when your tree needs to be watered by observing the foliage, testing the soil with your index finger just below the surface, or just by the weight of the pot. (The drier the tree, the lighter it will feel.) To take the guesswork out of watering, an inexpensive moisture meter which works very much like a thermometer comes in handy. Insert it into the soil and the movement of the needle will tell you if it is time to water.

Rainwater is best for watering plants, but tap water that has stood for a few hours is adequate. In summer, trees should be watered in the early morning or late afternoon to avoid the midday heat. This will prevent the leaves of the finer bonsai from burning. In winter, water early to permit any excess to drain before the night frost. Plunging the pot into a bowl to soak is ideal for recently potted trees, small collections and for trees that have dried out. Be sure to drain properly, however!

Because of limited space in the confines of a bonsai pot, bonsai care can be quite difficult. The shallow containers limit the expanse of the root system and make proper watering practically an art in itself. While some species can handle periods of relative dryness, others require near-constant moisture. Watering too frequently, or allowing the soil to remain soggy can promote fungal infections and "root rot". Sun, heat and wind exposure can quickly dry a bonsai tree to the point of drought, so the soil moisture should be monitored daily and water given copiously when needed. The soil should not be allowed to become "bone dry" even for brief periods. The foliage of some plants cultivated for bonsai, including the common Juniper, do not display signs of drying and damage until long after the damage is done, and may even appear green and healthy despite having an entirely dead root system.

Bonsai should not be allowed to become waterlogged, as this may lead to root rot. Neither should the soil be allowed to dry too completely before rehydration. Watering techniques vary, with some growers preferring to water with a fine rose on a watering can or hose, while others immerse their trees in a water-filled basin to the height of the container lip.