Container watering has to be done with care. The water needs of plants grown in containers are variable, and the use of containers allows plants limited self-correction if they are over or underwatered. Too much water can damage plants in a variety of ways, while too little water can be deadly. Container plants rely on people to supply them with the amount of water they need through appropriate container watering practices.
Before one starts evaluating container watering needs, it's important to make sure that plants in containers are being grown in the right kind of soil, and that conditions in the pot are appropriate. The container should have holes for drainage, covered by a layer of gravel or similar material which also promotes drainage. The soil should be appropriate for the plant, with a healthy balance of nutrients and soil amendments which promote drainage or promote water retention, depending on the needs of the plant.
When watering plants in containers, they should be watered until water runs freely from the pot. This is designed to reduce the buildup of harmful salts and other materials in the soil by rinsing the soil clean. People should watch out for plants with large root systems, as sometimes the roots create a ball which repels water, allowing water to flow around the soil, down the sides of the pot, and out the bottom. If a plant feels no heavier after watering than it did before, the water is not reaching the plant.
Some people use an automatic watering system for container watering. This is not advisable, because the needs of container plants can change so much. A plant may dry out in a few hours one day due to dry, warm conditions, and hold water for days at other times, when the weather is cool and humid. Plants should be checked before watering to see if they need water, and people should avoid container watering on a schedule, as this will not account for the variable needs of the plants.
It's also important to be sensitive to plant health. If a plant looks unhealthy, it may be time to reevaluate how it is being watered. Limp, yellowing foliage is a sign that a plant is not getting enough water, for example. Nutrient needs can also impact health; if a plant hasn't been repotted in some time, it may be necessary to repot with fresh soil to restore the balance of nutrients the plant needs, and to address issues such as soil compaction, which may be making it hard to access water and nutrients.