HERE ARE some answers to questions about fruits, vegetables and house plants that readers have written in:

Q. I have cherry tomato plants growing on my windowsill, planted them about mid-October, and they haven't even bloomed yet. What do you suppose is wrong with them?

A. Most likely, they have not been getting enough light. With the short days of winter, plus cloudy weather, they may not be getting enough day length, light intensity and light quality. On a cloudy day or under dirty or shaded glass, the plants may not receive enough light to bloom and develop fruit. No amount of fertilizer will help and extra light from a lamp will do little good because the intensity of the brightest light is much less than sunlight (something like 60 foot-candles compared to 6,000).

Q. Can impatiens plants be grown indoors during the winter as house plants?

A. It can be done. The major problem getting impatients to bloom indoors is insufficient light during cloudy winter weather. Artificial light, as from a floor light, will help. It's best to take cuttings from your garden plants in August and September to root for indoor use during the winter. Make the cuttings 4 to 6 inches long, make the cut just beneath a leaf where the stem is swollen. It can be rooted in a glass of water or sand. After it roots, it can be grown in water or in good potting soil.

Q. I'm going to plant some apple trees in the spring. Which ones are best for eating fresh and which for making applesauce?

A. Some of the best for eating fresh and for salads are McIntosh, Red Delicious, Rome Beauty, Jonathan and Stayman. For applesauce, Golden Delicious, Melrose, Yellow Transparent, McIntosh, Cortland, Jonathan, Grimes Golden, Stayman Winesap and Rome Beauty are considered very good.

Q. My dieffenbachia and two philodendrons don't look very good, they probably need to be repotted, how can I tell whether they do, and when would be the best time to do it?

A. Turn the plant upside down, tap the rim of the pot on the table and let the plant slide out. If roots are visible and matted, a change to the next size larger pot is desirable. But if the roots do not fully occupy the soil and cannot be seen, the plant may need to be changed to a smaller pot. The best time to do the repotting is in early spring. The packages of potting soil sold at large garden centers are suitable for repotting.

Q. I had three bell pepper plants in my garden last summer. My problem was: 3 to 5 days after the bloom drops, the fruit drops also. What caused this?

A. Almost invariably it is caused by hot, dry weather at the time the blossoms occur. Plants that bloom before the hot weather will be loaded with fruit while those that bloom later may have none at all.

Q. I picked my cucumbers while they were small last summer, but about one in three was so bitter it could only be eaten by slicing and salting.My soil is acid, was that the cause?

A. Usually fluctuations in temperature cause the bitter taste of cucumbers. Cucumber mosaic disease also can cause bitterness. The disease overwinters on pokeweed, milkweed and other weeds and in the spring is spread by aphids and other insects. Next summer plant a variety resistant to the disease, such as Burpee's M&M hybrid.

Q. I don't have much luck growing onions; the bulbs do not enlarge. What could be wrong?

A. If you are planting the bulbing type, your problem must be shade. Onions must not have any light obstruction if they are to bulb properly.

Q. I have two Bartlett pear trees, 6 and 10 years old, 20 feet apart, that are loaded with blossoms each year but produce no pears. What could be wrong?

A. Pollination is the problem. Bartlett pears bear little or no fruit unless cross-pollinated with another variety. Duches d'Angouleme is considered good as a pollinator for Bartlett.