Watering House Plants

More house plants are killed from improper watering than from any other single cause. When plants are overwatered, the soil remains saturated and root systems are unable to function properly because of lack of oxygen in the soil. Soil-borne bacteria and fungi invade the roots and eventually destroy the entire root system. The plant may struggle for months before it succumbs. Plants which do not receive enough water become stunted and woody, the leaves turn yellow and finally fall.

Watering frequency depends on the kind and size of pot, soil mix, environmental conditions and plant species, size and stage of growth. Plants in porous clay pots require more frequent watering than those in nonporous ceramic, metal, glass or plastic pots. Plants grown in small pots will require water more frequently than those in large pots. Soil mixes high in organic materials such as peat retain more water and plants grown in these mixes will not have to be watered as frequently as plants grown in mixes containing high amounts of sand or perlite. High temperature and low humidity will increase the rate of water loss from a plant and, consequently, increases the frequency of watering.

Generally, plants should be watered when the soil becomes dry to the touch . However, some plants, such as ferns, need to be watered before the soil becomes dry to the touch, while cacti and other succulents should remain dry for a few days between waterings. When watering is needed, water thoroughly. Apply enough lukewarm (room temperature) water until it runs out of the bottom of the pot. This type of watering washes excess salts out of the pot and guarantees that the bottom 2/3 of the pot is properly watered. Be certain that the potting soil drains well, and never allow plants to sit in a saucer of water.

Application of water to the top of the soil mix is the most common method of watering container plants. However, watering from the bottom of the container with the use of a saucer or tray is a method used by many homeowners. Watering constantly from below brings nutrient salts to the soil surface. An excess of these salts may accumulate in the upper soil layer in four to six weeks and this can result in burning of the upper roots and/or stem. It is a good practice, therefore, to water thoroughly from the top once a month to leach excess salts out of the pot.

Containers without drainage holes should have a layer of coarse gravel placed in the bottom to allow a space for excess water. Another method of using containers without drainage is the "double-potting" technique. Pot the plant in a container that has a drainage hole and is one inch less in diameter and shorter than the container without drainage (decorative pot). Place several inches of gravel in the bottom of the decorative pot and place the potted plant on the gravel layer.

Aggregates such as gravel or pieces of broken clay pot should not be placed in the bottom of a pot with a drainage hole. Research has shown that aggregate actually slows water movement through a pot rather than aiding it. A small piece of broken clay pot can be placed over the drainage hole to prevent soil from draining through the hole.