Experts emphasize the importance of knowing the origins and natural growing conditions of plants we choose for indoor gardening. Even within one plant family, such as Begonias, for example, cultural practices must be based on a knowledge of the differing environments where the plants originated.

The cultural problems of a reader who has written to me about the 30 plants in her living room point up the truth of those observations. John Falk, associate director of the Chesapeake Bay Center for Environmental Studies of the Smithsonian Institution, makes similar comments in an article entitled "Roots: The Saga of the American House Plant." He writes:

"It makes a difference to know that an asparagus fern comes from South Africa or that a button fern comes from New Zealand. The more you know about the environment in which your plants originally evolved the better you'll be able to meet their needs . . . Discovering such facts about your house plants' origins can be as challenging a task as any genealogical search. An informed approach based on knowledge of a plant's biology and ecology can only yield healthier, more beautiful indoor flora."

So - to the gardener who has 30 plants in her living room:

Much depends on you, but here are some guidelines to help overcome some of your problems while you are learning more about your plants.

You write that you water your plants once a week.

Plants cannot be watered on a set time schedule, especially such a large and varied collection. You must know the needs of the individual plants. Some plants do best if soil is allowed to dry moderately between waterings: others do best if soil is kept moist. False aralia and Jade plant, for instance, are very different in their requirements.

When you water, use tepid water. Pour it on until water comes out the drainage hole of the pot. Wait 20 to 30 minutes, then empty the saucer. Do not water again until the top inch or more of soil is dry. In addition to considering the type of plant, gauge frequency of watering by size of pot, kind of pot (clay or plastic) temperature, light and season of year.

Plants also need some moisture - humidity - in the air. Your apartment apparently is very hot and very dry.

You can alleviate the dryness by several means. Where plants are grouped together, set open containers of water inconspicuously among them; evaporation will add water to the air. Set pots on a watertight tray that will hold pebbles or sand kept constantly moist. Pots should not stand in water. Frequent misting will help increase the humidity. The bathroom is a good place to grow plants because the frequent use of water there maintains a higher humidity than elsewhere in the house.

Brown tips and margins of leaves are evidence of overwatering, underwatering, dry air or overfertilizing.

Bright indirect light is best. Full sunlight is injurious to many foliage plants.

You say you're afraid to try propagating plants by taking cuttings. You already have a book that tells how to make new plants from parts of old ones that have grown leggy. Be venturesome. Follow the instructions. Learn by doing.

Most foliage plants do not require feeding in winter. You seem to have overdone it. Short winter days do not provide enough light for plants to grow actively and they cannot use the fertilizer given. It accumulates in the soil and can cause a number of problems.

Do not fertilize a resting or dormant plant. Never feed an ailing plant.

Occasionally, perhaps every third or fourth feeding, omit fertilizer and instead liberally apply clear water to flush out unused fertilizer.

Your use of timed-release fertilizers may be causing some of your problems. With 30 plants, what kind of records do you keep in order to know when the time has arrived for feeding? Timed-release fertilizers were developed for use of nurserymen who grow plants to sell. These fertilizers generally are not practical for indoor gardeners who are gorwing a number of different plants, including some that require a rest period.

And finally, remember that "the ancestors of every houseplant in our homes originated in some ecologically unique section of the world." We must pay attention to each plant's "roots."