Foliage plants are excellent for indoor decoration because they are able to survive environmental conditions unfavorable to many other kinds of plants. The important elements are light, temperature, humidity, watering, fertilizing, insects and diseases. Here is the latest official information on how to take care of them.

Light intensity controls to a considerable degree the rate of food manufacture. Light duration also is important since the total number of footcandles of light received is a product of intensity and duration.

Several kinds of foliage plants can survive for a year in low-light areas. A low-light area is one with 50 to 100 footcandles, a location usually more than 8 feet from windows - no direct light, dull hallways.

A medium-light area is one with 100 to 200 footcandles, a location 4 to 8 feet from windows - an average well-lighted area.

A high-light area is one with over 200 footcandles, brightly lighted offices, areas within 4 feet of large windows facing south, east or west.

Artificial lighting is being utilized more and more in maintaining plants in locations where light is inadequate. If artificial light is used to supplement natural light, either incandescent or fluorescent light will give satisfactory results. If artificial light is the sole light source, both incandescent and fluorescent light should be provided.

The most desirable temperature range for foliage plants is 70 to 75 during the day and 65 to 70 at night. In general, plants require a lower night temperature than day temperature, although this does not appear to be critical for foliage plants.

Foliage plants grow best when humidity is 35 to 45 percent. Proper watering, temperature control and maintenance of light levels will do much to overcome adverse effects of low humidity, unless it is below 20 percent.

Humidification equipment attached to the heater or air circulation system is the best answer to the problem of low humidity. Other ways such as misting and placing pans of water with pebbles or gravel are not really effective.

Never allow the soil to become completely dry between waterings and when watering apply enough water to thoroughly wet the entire soil ball. The water should be at room temperature (tepid, slightly warm).

The frequency of watering for each kind of plant will wary. Even two plants of the same kind may have different water needs because of being in different environments.

Containers with drainage holes should be placed in a saucer and sufficient water applied at each watering until excess water drains out the bottom.

Containers without drainage holes should have a layer of coarse gravel in the bottom to allow space for excess water. A good way to check them is to lay them on their side in a sink and see how much excess water runs out, if any.

Two rules to remember for healthy plants are: Never allow the entire soil medium to become dry (the top 1/4 to 1/2 inch is acceptable), and never allow plants to stand in water.

Newly purchased plants should not be fertilized during the first three months in the home. Thereafter, two to four applications a year will be sufficient unless considerable new growth is desired and the plant receives more than 200 foot-candles of light. The new growth may be unattractive if the plant is getting inadequate light. Many types of fertilizer are available for foliage plants. Directions on the label for amount to use should be followed.

Spider mites, mealybugs and aphids are the insects usually troublesome on indoor plants. Putting a plant under the shower and rubbing the foliage with your hands should get rid of mites and aphids. It may be necessary to repeat the treatment weekly for several weeks.

Mealybugs can be disposed of with rubbing alcohol applied with a soft cloth. It kills the bugs without damage to the plant. Repeated treatments may be necessary weekly for two or three months to take care of new ones hatching.

In the dry air of the average home, few diseases are likely to affect foliage plants. The worst, and usually the only serious one, is root rot caused by over watering or poor drainage.

Excessive water results in oxygen deficiency in the soil, predisposing roots to infection by root rot fungi. If a plant is suspected of suffering from root, rot, wash the roots with running water. A healthy root system will appear fibrous with white root tips. A diseased root system will show blackened root tips with various degrees of soft watery rot. if the plant is all right, repot it; if it is infected, discard it.

When foliage plants are grown indoors, dust and other undesirable residues accumulate on the foliage and become unsightly. Sponge or wipe the foliage with a soft moist cloth. A small amount of hand soap may be added to the water when stubborn spots are encountered. Don't fold, crease, or rub leaves too hard as they may be damaged.

A cloth moistened with a little milk can be used to get shiny foliage if rubbed gently over the foliage of smooth-leaved plants.