How to Determine How Much Water Plants Need

As a rule, the soil for most plants should be somewhat moist about 3 to 4 inches deep (7.6 to 10 cm). This is important, as you need to make sure moisture reaches the roots of the plant. If the soil is not moist below 3 or 4 inches (7.6 to 10 cm), your plant may not be getting enough water.