Bonsai Watering Calculator

Unlike succulents, bonsai should never be allowed to dry out completely. Water when the topsoil feels slightly dry to the touch, typically every 1 to 3 days in summer and every 3 to 7 days in winter for most species. The thin bonsai pot and well-draining soil mean the tree dries faster than a normal houseplant. Check morning and evening during hot weather.

Water thoroughly until water flows freely from all drainage holes, which ensures the entire root mass is saturated. Then do not water again until the surface soil just starts to dry. USDA Extension and the American Bonsai Society advise against letting the pot sit in water (except for a few moisture-loving species), as this causes root rot.

Significantly. Tropical species like ficus and jade prefer to dry slightly between waterings. Junipers and most outdoor conifers prefer consistently moist but never saturated soil. Maples and elms are in between. The pot depth matters too: a shallow bonsai pot (3 to 5 cm deep) dries much faster than a standard decorative pot at the same tree size.

In summer, bonsai may need watering daily or even twice daily during heat waves. In winter, deciduous trees in dormancy need very little water; evergreen outdoor bonsai need occasional watering when temperatures are above freezing. Always check soil moisture rather than watering on a fixed schedule, as weather changes significantly affect evaporation rate.

Bonsai soil must drain quickly while retaining enough moisture for root health. Traditional Akadama clay (from Japan) is widely recommended; alternatives include a mix of coarse sand, perlite, and composted bark (2:1:1). Avoid regular potting soil, which compacts and prevents oxygen reaching the roots. University horticulture extension guides recommend particle sizes of 3 to 6 mm for bonsai mixes.