Growing indoor plants from seed in fun for many between the ages of eight and about 88. Orange, tangerine, grapefruit and lemon are some of the best to work (or play) with. Full-grown with their glossy, dark-green foliage, they are perfectly stunning with flowers and fruit on them.

Of course, they get too big and probably are too much trouble for the average home; but you won't have to worry about that for several years, because it taken time to get them to large sizes.

You can use seeds taken from fruit bought in grocery stores. Citrus seeds are injured by drying, so leave them in the fruit until you're ready to use them.

If they can't be planted immediately, keep them in cold water for a few days, but change the water daily. When they must be held longer, put them in the refrigerator in a plastic bag at 40-degree to 45-degree F.

Plant three or four seeds in a 3-inch pot or six or eight in a 6-inch pot. Six or eight in a 6inch pot. Six or eight small tangerine or grapefruit plants in a small pot would make a very nice centerpiece.

A 50-50 mixture of good soil and sphagnum peat is satisfactory for planting them. If you don't have it, use the potting soil many supermarkets sell for house plants.

Cover the seeds with 1/4inch to 1/2inch of soil. The seed bed should be kept moist but not soggy wet. A soil temperature of 70degree to 8/degree is best; germination is delayed if the temperature is much below 70degree.

It takes about 30 days for germination. Keep the pot in a shady place until the plants start to come up, and then move them into very good light, preferably some morning sunlight.

A coffee plant can make quite a conversation piece, and is fairly easy to start yourself if you can find some unroasted coffee beans. Even bettter are ripe cherries from a coffee plant growing in a botanical garden, which sometimes can be had for the asking.

Remove the pulp from the seed by hand. After pulping put them in a glass of water overnight. The next day wash them in clear water and plant at once.

If sphagnum is used, it's necessary to start fertilizing as soon as seedings appear, ususally in six to eight weeks. Give them a weak nutrient solution every week. When the seedings have four leaves, plat them in individual pots, using a mixture of good soil and peat.

Q -- A year ago I was given a gloxinia in bloom. When it finished blooming, it died back for the winter. When sprng came, it sprouted and grew to about two feet, blooms formed but they died and fell off. How can I get my gloxinia to bloom ?

A -- When the gloxinia dies back after blooming, it should be stored in a cool, dark place for two or three months and then brought out and repotted. It needs very good light -- either a sunny window or artificial light -- and without it there will be no flowers and the plant will be quite leggy. At this point, your plant probably has been ruined.

Q -- What is the big problem when the garden soil becomes too acid ?

A -- As soil acidity increase, iron, aluminum and manganese become more soluble and available soil phosphorus combines with these elements to form insoluble compounds, resulting in a phosphorus deficiency. The bacteria that decompose organic matter, those that decompose organic matter, those that produce nitrate, and those that fix atmospheric nitrogen become less active. The rate of soil fungi to bacteria increases and the working qualities of the soil tend to deteriorate with adverse effects on aeration and drainage.

Q -- We don't have a vegetable garden. Can we grow some lettuce in tubs? The home-grown kind is so much better than that you buy in the supermarket .

A -- Lettuce can be grown in containers, but you won't get very much of a crop. Why not plant loosephead lettuce as an edger for your flower garden? As you harvest the lettuce in the spring, replant with marigolds or some other dwarf annuals. Toward the end of the season, replace some of the flowers with lettuce for fall salads.

Q -- When is a good time for me to take rose cuttings ?

A -- Late August and early September are good times. Miniatures, climbers and amblers are easy to root; hybrid teas are more difficult.

Q -- I would like to grow some nicotiana like Nicki Rose in pots on my windowsill. How long does it take from sowing seed to bloom ?

A -- About three months. Seeds need light for germination and take about 20 days to sprout.

Q -- We have a new home and want to plant a tree for shade, one that will grow fast, one that we can enjoy ourselves as well as our children. We have been told to plant a silver maple. It is a good tree ?

A -- Under good conditions, the silver maple may grow as much as eight feet in a single season.It's sometimes advertised as "the beautiful silver maple that will grow as high as a house in a single season." Due to this vigorous growth, the tree is very weak-wooded, and as it reaches considerable size its brittle properties become a significant hazard in wind and ice storms. The opinion of many specialists is that it should not be planted near homes or streets and shoul be used only where other trees will not grow. It has a shallow root system, which makes it difficult to grow grass nearby and uproots sidewalks and may crack foundations of houses or clog drainage systems.

Q -- Can cherry tomatoes be grown inside the house in pots in winter ?

A -- Yes, if you have a sunny windowsill. To insure pollination, shake or thump the flowers daily when the plant begins to bloom.

Q -- There's a white cottony substance on the leaves of my African violets. What is it and what and I do about it ?

A -- The white cottony substance is the secretion of mealybugs. Use a cotton swab dipped in rubbing alcohol on each of the leaves -- it will kill the insect without damaging the plant. You'll have to repeat applications weekly for several weeks because of additional bugs hatching from eggs.

Q -- I'm growing coleus on my windowsill and I can't make the plants grow upright .

A -- When a plant is near a window, the stem of the plant bends toward the light. If the plant is turned a quarter-turn to half a turn each day, the stem ususally grows straight.