Three books of considerable interest to gardeners have been published recently. One is about orchids, one about propagation of plants and the other about gardening in containers both indoors and outside.

"Orchid Genera Illustrated," by Tom and Marion Sheehan (Van Nostrant Reinhold, 207 pp, $29.95).

Tom Sheehan is professor of ornamental horticulture at the University of Florida, former president of the Florida-Caribbean Orchid Association, a consultant for the Food and Agricultural Organization of the United Nations, the author of two previous books and more than 200 scientific and popular articles.

Marion Sheehan is a free-lance botanical illustrator and a part-time professor of ornamental horticulture at the University of Florida. Her botanical illustrations have been published in many books devoted to botany and horticulture, exhibited at numerous shows in the U.S. and abroad, and a recent series of prints of her works is being sold internationally. She and Dr. Sheehan have traveled extensively to collect and photograph orchids and to lecture to orchid societies around the world.

The book contains 61 exquisite color pages of the more commonly grown orchid genera with detailed descriptions of each, using a minimum of technical terms. More than 50 additional black-and-white drawings show specific vegetative and flowering characteristics of individual species. An extensive, illustrated glossary describes more than 200 terms used in orchidology.

"What we have attempted to do," they say in the introduction, "is to depict in both words and illustration the more commonly grown genera of orchids. Each genus is described . . . in terms that the average person can understand without having a degree in botany or taxonomy.

"Since there are over 800 genera in the Orchidaceae, this book is only the beginning."

"How To Progagate Plants," by Jack Plumridge (Lothian Publishing Co., Melbourne, Australia, distributed by ISBS, P.O. Box 555, Forest Grove, Ore., 97116, illustrated, 214 pp, $12.95).

This is a good book with a lot of interesting and important details that you do not find in most books on propagation.

Plumridge was on the staff of the Burnley Horticultural College as a propagator and remained in charge of the nursery section for 20 years. While at Burnley he lectured on plant propagation and started writing articles for gardening journals.

Many of the plants included in the book are not grown in the U.S., but the majority are, including trees, schrubs, perennial flowers and house plants. t

The main attributes of the book are: it is complete, easy to read and understand, and accurate.

Seedlings take longer to flower and bear fruit than those propagated from cuttings, layering, budding and grafting, the author says. Seedlings raised from hybrids generally produce a mixture of flowers and fruits usually much inferior to the parent plant.

If the root system of a seedling is examined it will be seen that it is entirely different from that of a cutting, he says.

When a seed germinates the first thing it does is send a root down into the soil. This becomes the main taproot of the tree. A shoot goes upward into the air and becomes the main stem of the tree. The taproot strikes downwards deep into the soil. Once the taproot is cut or wrenched, it never grows as a true taproot again but generally breaks into a mass of fibrous roots.

Trees and shrubs from cuttings do not have any taproots at all. Roots are simply formed on the stem of the cuttings and develop into fibrous roots. Usually, but not in all cases, trees and shrubs from cuttings are much more easily transplanted and handled than those raised from seed..

"Tub Farming -- Grow Vegetables Anywhere in Containers," by Mary Johnson (Garden Way Publishing, 9503 Ferry Road, Charlotte, Vermont 05445, 112 pp, illustrated, $5.95 paperback, can be ordered direct from publisher).

This concise how-to book will guide you through the maze of gardening techniques, enabling you to grow plants successfully anywhere without a outdoor garden, the author says.

"Convenience, taste, fun, decoration, economy, a soothing atmosphere, all are good reasons to begin farming in tubs," she writes "This Tub Farming book is meant to be a guide to help you grow the most successful vegetables with the least amount of work.Only the most successful, convenient, time-saving techniques are presented. You can always think up more elaborate, complicated routines on your own without the help of a book. Give it a try -- it's easy and your kids will no longer believe that carrots grow in plastic bags."