The no. 1 killer of house plants is overwatering. Foliage plants are adapted to regions where soil is moist but not constantly saturated with water. a

Soils should not, however, become completely dry between waterings. When watering, apply until it comes out through the drainage holes at the bottom. Wait about 15 minutes for excess water to drain and empty the saucer. Don't allow the pot to stand in water for long.

If the pot has no drainage holes, lay it on its side in the sink to allow excess water to escape.

Too little or too much light also can cause serious damage. Low light is a particular problem during the winter because of short and cloudy days.

This situation can be modified by the use of artificial light. A second option is to learn the requirements of the plants desired and buy only those that will grow under the light levels that can be supplied.

Without ample light, photosynthetic processes are inadequate to produce sufficient food for plant growth. The plant must utilize stored food and deterioration of plant quality occurs until reserves are consumed and death occurs.

Light intensity controls to a considerable degree the rate of food production; generally with more light, more food is produced. When natural light is inadequate, it should be supplemented with artificial light.

Light duration also is important; the total amount of light received is a product of intensity and duration. Therefore when plants are grown in low light areas they should be lighted for longer periods to compensate for low intensity.

Artificial lighting is being utilized more and more to highlight and aid in maintaining foliage plants. The Gro-Lux and other specialty fluorescent lamps have been designed to produce the light quality necessary for plants and can be used in place of incandescent and fluorescent combinations.

The most desirable temperature range for foliage plants is 70 to 75 degrees F. during the day and 65 to 70 at night, which is similar to normal conditions in most homes.

Foliage plants grow best where the humidity is high. However, proper care in watering, temperature control and maintenance of light levels will do much to overcome low humidities common in most homes. Q: I have a Stayman Winesap apple tree in my yard, and my neighbor a block away also has one. Are the trees close enough to pollinate each other? A: The two trees are of the same variety, and most apple trees will produce little or no fruit unless their blossoms have been pollinated by a different variety nearby, such as Golden Delicious. In the meantime, get a handful of bloom branches from a different variety of tree if available, put the branches in a can of water and hang them in your tree. Bees will do the rest. Q: Last summer we had a very nice garden, but white grubs ruined our carrots and potatoes. How do we get rid of them? A: Probably the carrots were damaged by root maggots. Before planting seeds apply Spectracide spray to the soil surface and mix thoroughly with the upper four inches of soil. Follow directions on the label for mix and application. Probably the damage to the potatoes was caused by the larva of white-fringed beetles. Treat infested soil with Spectracide according to directions on the label for white grub control. Q: We saved some seeds from Northern Spy apples to plant this coming spring. They're stored in a jar in the closet. Do you have any advice on how to plant them? A: Apple seeds must receive a cold treatment or stratification for 60 to 70 days at temperature of 32 to 45 degrees before they will germinate. This treatment is to overcome internal dormancy. However, you haven't lost anything because the seeds would not come true if they germinated. Q: What is the best way to get rid of moss? How soon after can I seed the area for a lawn? A: Normally moss is present in lawns because conditions are not suitable for growing healthy grass. The only permanent control of moss is to correct the conditions that cause it: poor soil fertility, poor drainage, little light, soil compaction, poor air circulation or a combination of them. Ammonium sulfate or copper sulfate can be used to burn off the moss, but the moss will probably return if the cause is not corrected. The first step is to have your soil tested, and go on from there. Q: What kind of ground cover is best under an oak tree to prevent the soil from washing away? It's on a slope and a lot of leaves fall on it starting in late summer. A: English ivy will hold the soil once established, but there would be a problem raking leaves from it. Perhaps a deep mulch of woodchips or ground bark would be best. Q: I love voilets and want to raise some of them. Any suggestions? A: They do best in fairly good soil, light shade and lots of water. They stop blooming when a clump is too big big and needs dividing. Q: We want to grow tomatoes in our backyard this year. Should we buy plants or start them ourselves from seeds? What kinds are best? A: If you know how to do it and can provide the proper environment, starting the plants from seeds has advantages. Otherwise, buy plants. Better Boy is one of the best; it has disease resistance, very good flavor and produces a lot of fruit. Q: My rhododendron has become leggy. Can I prune it and if so, when is the best time? A: The rhododendron can be pruned immediately after it blooms and can be cut back almost to the ground. Pruning encourages new growth and results in a nice landscape plant.