News Article 
News Article
By Dr. Leonard Perry, Extension Professor
University of Vermont
Of all the things done to houseplants, watering
is probably the one cultural practice that causes the most problems. The
type of soil used as a potting medium affects watering, as does light exposure,
temperature, and humidity.
Many factors determine when a plant needs to be watered. Just as many environmental factors change with the seasons, so do the water needs of plants.
The two main aspects of watering to be considered are frequency of watering and amount of water applied. The watering frequency is simply how much time passes between waterings. The frequency will vary over the course of the year.
Avoid watering on a fixed schedule such as every week or every five days. A fixed schedule does not necessarily give plants water when they need it. In fact, watering on a fixed schedule may mean plants are overwatered at one time of the year but underwatered at others.
With few exceptions, plants should be watered when the soil feels dry to the touch. This means the frequency of watering will vary with the rate at which the soil dries out.
Apply enough water so some comes out the drain hole at the bottom of the pot. This flushes out salts that can lead to root injury. Do not let plants sit in excess water. It will be reabsorbed and, thus, the salts dissolved in the water will be reabsorbed.
There is no easy way to tell when plants in undrained containers have had enough water, but the actual technique for watering is not difficult. The best way is to use a watering can with a long, narrow, spout. This allows the placement of water on to the soil.
Watering plants with dense foliage will be more difficult if this type of watering can is not used. Try not to put the water on the leaves and crown, as rot diseases are more likely to occur if water is continually poured on the crown. For watering, tepid water, or water near room temperature is best.
Bottom watering is a practice where the plant is set in and absorbs water from a container filled with water. Plants regularly watered from the bottom should occasionally be watered from the top to get rid of excess salts in the soil. The bottom layer of soil becomes saturated when a plant continuously sits in water. Any roots growing in this saturated layer will die. The soil available for plant growth is thus reduced.
Some plants enter rest periods at some time of the year. Resting plants may use less water so are more likely to be overwatered. If a plant slows or stops growing in late fall or early winter, it may be entering a rest period.
At the same time the furnace may start running and dry the air out, causing the soil to dry out more quickly. Concern about overwatering resting plants in winter must be tempered by consideration of the effect of lower house humidity.
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