As summer progresses, the amount of light and heat your indoor plants receive changes from week to week. Some plants may need to be moved from a too sunny window. Turn and rearrange plants so that all get the benefit of the best light available. Most plants will be actively growing and will require water and fertilizer more often that they do in the short, dark days of winter.

If potted plants seem constantly to require watering, check to see if they need repotting.

Wipe leaves of smooth-leaved plants with a damp cloth to prevent dust clogging their pores, and to restore a healthy sheen. Hairy leaves can be brushed gently with an old toothbrush.

Protect plants from cold drafts of airconditioning vents.

Check all plants for insect pests and treat any that need it. Use pesticides outdoors if possible.

Brown leaf tips of chlorophytum and dracaena can be trimmed with scissors to their natural contours to improve appearance.

Clean pebble trays and pebbles. Wash both in a diluted solution of household bleach (1 cup bleach to 10 cups water), then rinse with clear water.

Carry out a thorough housecleaning of the fluorescent light garden. Unplug fixtures; wipe the tubes and frames with warm soapy water. Disinfect trays or pebbles as suggested above. Clean table tops of plant debris, solid crumbs and fertilizer or water stains.

Plan ahead for your indoor fall and winter garden. Take inventory of the accumulation of plants. Make room for new acquisitions by disposing of overgrown specimens or of those that have lost their appeal to you. If the idea of throwing plants away disturbs you, donate the healthy ones to a plant sale, nursing home, youth hobby groups or senior citizens club room. Take cuttings of overgrown plants of species which you want to retain in your collection so that you will have young vigorous plants to start the new season indoors. Summer Pests.

Indoor gardeners often ask: "How do these bugs get into the house?"

The answer: on you, on pets, on flowers brought in for decoration, on newly purchased plants or plants traded with friends - even on the breeze through open windows and doors.

If insect pests are on your plants outdoors, you can unknowingly bring them inside. And if you are battling them outdoors this summer, extra precautions should be taken before moving the plants indoors when summer ends.

No one purposely spreads plant insects and disease. But the Animal and Plant Health Inspection Service of the U.S. Department of Agriculture warns, "In their desire to get new varieties or to increase their stock, gardening enthusiasts occasionally forget that trading plants can result in the spread of plant pests." A Reader's Question

Allan Scott, Arlington: I would like to know where I can get elfin herb and cigar flower plants.

I have a clivia which bloomed last year, but this year no bloom. Why? It is growing okay.

A. Because consumer demand is lower in the summer months, a varied and extensive selection of plants is not always available at plant stores. This is probably the reason you have been unable to locate elfin herb and cigar flower recently. Also during the summer months, growers are busy propagating quantitites of plants to supply the demand which will come when the indoor gardening season commences in earnest.

Proper fertilizing is one key to production of flower stalks on Clivia. About a month after blooming, the plant becomes dormant and should be allowed to rest without fertilizer and with minimum water for three months or longer. Resume normal watering and feeding in January, February or March. Use a balanced, watersoluble houseplant fertilizer monthly.

When Clivia is dormant it gets along with less water but never so that the large strap-shaped leaves wilt. If you kept your potted clivia outdoors last summer, it may have been excessively watered during it dormant period which could have contributed to failure of flowering in 1978. Be careful not to over water it during this year's dormant period.