It's commonly believed that more people kill their houseplants by over-watering than any other form of plant abuse. Watering houseplants correctly is really very easy, though. Begin by growing them in containers that have drain holes[1]. Then, no matter which type of plants you've got, water them until the moisture seeps out those drain holes[2]. Wait several minutes and spill out any extra water that might be left sitting in the tray or saucer beneath the pot. A kitchen baster helps to siphon excess water from a large heavy container.

The distinction between different houseplants is not in how they are watered but how often. Some plants - ferns or African violets, for instance - need attention as soon as the soil surface begins to feel dry. In contrast, cacti and succulents thrive when the soil is allowed to get quite dry between waterings - however, not bone dry.

Most plants fall somewhere between these two extremes. Allow soil to dry perhaps an inch or so below the surface, depending on pot size, before watering thoroughly again. The goal is to allow air to penetrate the soil, bring needed oxygen to the roots. When soil stays wet too long, anaerobic micro-organisms can take over, rotting the plant's roots. [3]