Since green is a color of Christmas, the spirit of the holiday season is frequently expressed through living plants.Indoor gardeners, who enjoy green plants the year round and use them to enchance their surroundings, should have little trouble including the plants in Christmas decorating.

At Christmastime, indoor plants, especially foliage plants, can become an integral part of the seasonal decorations, with or without added touches of tinsel and trinkets.

The Norfolk Island Pine can be your perennial Christmas tree. (Suggestions for trimming were given in another column.)

Other indoor plants can be incorporated in your decorating in a number of ways.

It is practically and aesthetically inadvisable to burden plants with ornaments that may damage plants or compete with their natural beauty. But some lightweight and small-scale ornaments may be added effectively.

Set lengths of flexible, silvery wire, such as that available in craft shops, in the soil around your spider plant and attach tiny, colorful baubles at the ends of the wires. Voila! A fountain of color when the baubles are set in motion above the plant.

String miniature lights - clear or colored - in the branches of Ficus benjamina. Add a colorful 3-inch glass bird or two. Handsome ones, made in Czechoslovakia, are available locally. The birds are fashioned with clamps for easy attachment to branches.

Trim a jade plant. I'm trying a gilded Czechoslovakian peacock with bows of gilt cord, but may decide that my Kabuki dolls or other Japanese mementoes are more in keeping with the bonsai planting.

Slip branches of holly or sprigs of mistletoe into a grouping of foliage plants on a mantel or low table. A red velvet bow attached to a plant stake in Boston fern or dieffenbachia will add a festive touch.

On a shelf of a room divider, trail a vining pothos around a non-drip candle with a sprig of holly.

Use several small pots of ivy enlivened with holly as a centerpriece for dinner or party table.

Arrange small specimens of peperomia, table ferns, ivy, philodendron or pothos as background for a tabletop nativity scene.

Even a palm can be brought into the picture by trimming it with bows, tinsel or, with restraint, some shiny ornaments. Many palms produce large bunches of orange seeds; perhaps you can find a way to use bittersweet berries or orange pyracantha berries to give a fruitful appearance.

Decorating and other activities of the season may require moving plants from their accustomed places. Such changes may alter light, temperature and humidity conditions. The indoor gardener should be alert to possible effects in changing environments and should return plants to their preferred locations as soon as possible.

As you plan your Christmas decorations, you may consider buying some plants.A redberried Ardisia crispa for Christmas color and year-round beauty as a flowering foliage plant will make a nice gift for yourself or someone else. A blooming Amaryllis will make a bold statement amongst your other greenery.

If you're thinking of buying greens for the office Christmas party, why not choose an exotic ornamental tree, such as Ficus or Schefflera. It will give pleasure for years to come and is no more expensive than a cut evergreen tree which will have to be disposed of all too soon.

And a word of caution. Be careful of investing in a living Christmas tree in a nursery container or pot. It is very difficult to keep a living Christmas tree (which is an outdoor plant) in the house during the holiday season in sufficiently good condition for it to survive outdoor planting after Christmas.

Happy holidays to all!

John A. Beglin, Alexandria: "I have an enormous spider plant which has produced little plantlets profusely for over a year. About five or six inches above one of the plantlets there is what appears to be a seed pod. Is it in fact a seed pod? Is it possible to produce additional plants from seeds."

A. The spider plant does sometimes set seed along the stem on which the small white flowers have bloomed. Collect the seed and sow in a shallow container of growing mix; keep it warm (70 degrees) and slightly moist until seeds sprout. Then give seedlings bright light and feed them monthly with balanced houseplant fertilizer diluted to one-quarter the strength recommended by the manufacturer. When large enough to handle, transplant the seedlings to individual pots or several to a pot as you prefer.

Charles L. Braund, Hillcrest Heights, Md.: "All summer my begonia plant was out on the balcony and it was very healthy. Now that I have brought it in it is in sad shape but not dead. This occurred in about a week. What happened? Will it come back?"

A. I assume you refer to the wax begonia which is the most popular balcony begonia. Bringing a large lush plant directly into the house from its outdoor location is a traumatic experience to the plant. Conditions of humidity and especially of light are radically different and less favorable indoors. it would have been advisable to cut the plant back at the time it was brought in.

If there is still some live green growth, take some cuttings and root them in water to start new plants. Cut off the withered or dead parts, almost back to the surface of the soil; give the plant a bright, warm location, keep the soil moist, and new growth should develop from stems near the soil surface if they are still fresh and green.

Charles Rademaker, Arlington: "Can I bring pots of chrysanthemums and geraniums indoors for the winter? If so, do I cut them back, transplant them, or give them any special care? Will the geraniums continue to bloom?"

A. The geraniums should have been moved indoors some weeks ago to allow time for adjustment to the changed environment before the furnace was turned on. With bright light or direct sunlight in a south window they may bloom. If the plants are as large as geraniums frequently become outdoors, it is advisable to prune them somewhat when bringing them indoors. Ordinarily, it is preferable to take cuttings of geraniums in late summer to start new plants to be carried over the winter.

Chrysanthemums are perennial garden plants and are not suitable for indoor gardening. If you have outdoor garden space, plant the mums in the garden, mulch them over the winter, for bloom outdoors next fall.