Watering plants is perhaps the most crucial element of houseplant care, and probably the one most fraught with errors and misunderstandings. All plants need water to live. And there are many people out there who simply forget to water their plants. But overwatering is probably an even bigger problem. Plants need to drink deeply when they drink. But their rots cannot sit in water or the plant will rot and die. So how do you know when to water? First, it's a pretty safe bet that most plants can be watered about once a week. Perhaps a little more so in summer, and less so in winter. When you water, you want to water deeply. Pour enough water in the plant so that it runs out. If, after an hour, the plant is sitting in water, drain that. Otherwise, give the plant about an hour of being watered deeply, then drain. Then do not water for awhile, so that roots may get air in between waterings. There are things you can do to make watering easier. With finicky plants like African violets, it helps immensely to set the plant pot on a bed of rocks, with a wick sticking out of the bottom of the pot. (See the African violets page for a picture of this.) A terrarium also helps with watering, because it conserves moisture. However, keeping track of your plants is probably the best way. There are commercially offered devices that will tell you when your plants need water, but a good old-fashioned finger in the soil works well too. If it's dry a few inches down, it's probably time to water.