Coming up with the "World's Greatest Gardening Gifts for Christmas" would seem like an easy task. After all, there are thousands of different trees, shrubs or perennials, but the fact that it is winter makes them unlikely candidates to put under the tree. Seeds, in all their varieties, are other possibilities, but most local nurseries will not have those for sale until spring planting weather arrives.

Houseplants are options, but not all gardeners are converted to the joys of indoor growing. The last complication is that some of the most avid gardeners seem to have everything they could ever want or need to do with gardening. Finding anything for them that is not a trinket or a dust collector seems quite remote.Since winter is upon us, the best possibilities are inside gifts. Books are always one of my favorites, so I will share a few titles that I think most gardeners would enjoy.

My personal favorite for the year has to be a monumental publication done by the American Horticultural Society. This publication, "A-Z Encyclopedia of Garden Plants," is a comprehensive work of exciting proportions. Editors-in-chief Christopher Brickell and Judith D. Zuk drew on the expertise of more than 50 international experts to help with this volume. It covers more than 15,000 ornamental plants and is illustrated by nearly 6,000 color photographs. The descriptions are well done and the photography is carefully selected to illustrate and show vital plant information. This is not a book for the faint of mind or of body and has almost 1,100 pages. Perusing it fosters an appreciation for the vast number of plants that are utilized in the garden. My copy, a treasured gift from dear friends, will have a prominent place in my library for years to come.

Since this volume covers only ornamental plants, I must mention other selections for those gardeners who prefer growing fruits and vegetables.

Searching for specific cultivars or varieties of perennials, shrubs or fruit trees can be frustrating. Finding the plants is a lot easier if you use a good reference book. While I am not suggesting you need these books to find most plants, they can be valuable when trying to locate obscure, difficult-to-find plants.

"The Fruit, Berry and Nut Inventory" is a comprehensive compilation of 309 mail-order nursery catalogs. This 520-page book contains information on 5,810 fruit, berry and nut varieties. Each listing includes a plant description, history and a list of U.S. companies currently offering the variety. The nursery listing includes the company's name, address, price of the catalog, type of nursery (retail or wholesale) and a brief description of the types of plants sold by the company. "The Fruit, Berry and Nut Inventory" is available from the Seed Savers Exchange, 3076 N. Winn Road, Decorah, IA 52101. The price is $22 for softcover or $28 for a hardcover copy postpaid.

Also available from the Seed Savers Exchange is "The Garden Seed Inventory." This 502-page book provides information and sources of 5,797 standard or non-hybrid vegetable varieties. Soft-cover copies are $22 and hard-cover copies are $28 postpaid.

"The Anderson Horticultural Library's Source List of Plants and Seeds" offers sources of more than 47,000 plants available from more than 400 nurseries in the United States and Canada. The 261-page book lists the sources of annuals, perennials, vegetables, fruits and woody ornamentals. These include more than 2,000 daylily varieties and 250 varieties of tomatoes. The nursery and seed catalog source list includes the company's name, type of business (retail or wholesale), price of catalog, address and telephone number. This text is available for $34.95 from the Anderson Horticultural Library, Minnesota Landscape Arboretum, 3675 Arboretum Drive, Box 39, Chanhassen, MN 55317.

For those who are strictly indoor-gardening enthusiasts, there are a number of excellent houseplant publications availble. "The Reader's Digest Indoor Plants: The Essential Guide to Choosing and Caring for Houseplants" is an excellent new work published this year. It has three sections that offer advice on selecting, using and caring for plants. The first focuses on what plants to use, where they fit nicely in the home and how to use them as part of the decor. The second section is a plant directory that details more than 300 popular plants for indoor growing. The final section offers many plant-care ideas on creating an environment that will help them grow well in the interior environment.

P.S. In case you are wondering what could represent the last Z entry in the plant encyclopedia, it is about zygotealum, a caper bean that is an epiphytic orchid from South America.