Back-yard gardeners seem to grow more tomatoes than any other fruit or vegetable. But at the threat of the first frost, many gardeners harvest their other crops while they leave the green tomatoes to turn mushy on the vine, believing they are good for nothing.

Although "green" evokes images of freshness, vitality, delicacy and tenderness in association with other vegetables, when it comes to tomatoes, "green" is a dirty word. It conjures visions of unripe immaturity, of sickly biliousness, as in "green around the gills."

Unfair. Green tomatoes can make good eating. When frost threatens for the first time, usually sometime in mid-October, pick all the unripe tomatoes, whatever their stage of maturity, sort them by size and firmness and start cooking.

In her book "Edible Landscaping" (Sierra Club, 1982), Rosalind Creasy suggests pulling up the entire tomato plant and hanging it "fruit and all" from the rafters in a cool garage where the tomatoes will ripen. Others think a sunny window is the perfect place to ripen green tomatoes. Or you may prefer to put them in a dark place wrapped in newspaper or inside a brown paper bag or a plastic bag with holes punched in it.

If the tomatoes are full-size when picked, the natural ethylene gas the tomatoes emit should turn them red, ripe and juicy. But even with these efforts, some of the tomatoes will turn moldy and others will never ripen properly. In fact, those that are not full-size will never reach their potential.

That's the problem with many commercial tomatoes, which often are picked before maturity and colored with gases but not actually ripened.

With all these opportunities for disappointment, why wait for your green tomatoes to ripen? Eat them green. Ralph Waldo Emerson wrote in 1856 that tomatoes, like the sea-life and olives, are an acquired taste; similarly, you just have to give green tomatoes a chance.

Sicilians, for example, prefer partially ripe tomatoes that still show quite a bit of green because they consider ripe tomatoes too sweet for salads and suitable only for sauces. In the southern and midwestern United States, green tomatoes dipped in cornmeal or flour and fried are one of the treats of the growing season. And the Pennsylvania Dutch perfected a green tomato mincemeat pie.

Green tomatoes can also be "put up" for winter enjoyment. The crunchy, spicy taste of kosher-style pickled tomatoes, a staple of New York delicatessens, gives a tangy lift to a dull sandwich. For this easy-to-prepare condiment, the tomatoes should be small and hard, unripe, with no hint of red or yellow (telltale signs that they have begun to ripen).

If you like, you can make your own green tomato marmalade and green tomato relish, sweet or salty, according to your preference. Connie Naron, spokesperson for Cox's Relish Co., advises that it is most important to cook the tomatoes until they turn from bright green to olive green before packing.

In their book about "artisan-made" foods called "Food Finds" (Harper Colophon Books, 1984), Margaret and Allison Engel praise Cox's green tomato pickles made with large, firm chunks of tomatoes, onion and peppers in a spicy sweet and sour sauce as well as the sweetish green tomato chowchow with finely chopped ingredients. They are delicious.

Naron suggests serving the relishes Texas-style with fried catfish. Although this company is strictly local in retail distribution, you can order a pack of six 16-ounce jars by calling (214) 645-2701. KOSHER-STYLE PICKLED GREEN TOMATOES

Firm green tomatoes

Water

PER QUART WATER:

2 tablespoons coarse salt

1 teaspoon pickling spice

1/2 teaspoon mustard seeds, bruised

1/4 teaspoon black peppercorns, bruised

1 handful fresh dill with flower heads (add 1/4 teaspoon dill seeds if dill lacks flowers)

1 unpeeled garlic clove, flattened

Wash tomatoes and place in a large crock or bowl. Add enough cold water to cover tomatoes by 3 inches. Drain water, measure to see how much there is and pour into a saucepan. For each quart, add suggested amount of salt, pickling spice, mustard seeds and peppercorns. Bring to a boil and simmer 5 minutes. Cool completely. Prick each tomato with a fork in several places. To tomatoes add dill and garlic. Pour brine over tomatoes and place a heavy plate on top to keep tomatoes submerged.

Cover bowl loosely with a towel and let tomatoes stand in a cool place 1 to 3 weeks or until they are pickled to taste. Check tomatoes daily, skimming off any white foam that may form. When ready, transfer tomatoes to sterilized jars. Add strained brine to cover, adding dill from the pickling process. Cover and refrigerate. Will keep, refrigerated, for several months. Adapted from "Better Than Store Bought" by Helen Witty and Elizabeth Schneider Colchie (Harper and Row, 1979) SICILIAN TOMATO SALAD (4 servings)

4 large half-ripe tomatoes, sliced

1 red onion, thinly sliced

2 tablespoons capers

2 tablespoons chopped fresh parsley

2 tablespoons chopped fresh basil or 1/2 teaspoon dried basil

1/4 cup red wine vinegar

1/2 cup olive oil

Salt and pepper to taste

Arrange tomato slices on a serving dish. Separate onion slices and arrange over tomatoes. Sprinkle with capers, parsley and basil. Beat together vinegar, oil, salt and pepper and pour over tomatoes. Serve immediately or marinate in refrigerator several hours. GREEN TOMATO MARMALADE (Makes 5 pints)

3 quarts green tomatoes, peeled and sliced

6 cups sugar

1 teaspoon salt

6 lemons

2 cups water

Combine tomato slices, sugar and salt in a large saucepan. Peel lemons and slice the peel into very thin strips. Combine peel and water to cover in a small saucepan. Bring to a boil and cook 5 minutes. Drain and add tomatoes. Seed and slice lemon pulp and add to tomatoes. Bring tomato mixture to a boil, reduce heat, and cook, stirring, until thickened, about 45 minutes. Pour into hot sterile jars and seal. Store in refrigerator. Adapted from the "The New York Times Cookbook" by Craig Claiborne (Harper, 1961) $/ BAKED GREEN TOMATOES (4 servings)

6 green tomatoes

Butter for baking pan

Salt and pepper to taste

3/4 cup dry bread crumbs

4 tablespoons olive oil

2 tablespoons chopped fresh basil or 1/4 teaspoon dried basil

1/4 teaspoon thyme

1/2 teaspoon oregano

1 garlic clove, finely chopped

Cut tomatoes into 1/2-inch thick slices and arrange in a greased baking pan. Sprinkle with salt and pepper. Combine bread crumbs, oil, basil, thyme, oregano and garlic. Spread over tomatoes. Bake in a 350 oven 45 minutes or until tomatoes are cooked and top is browned. $/ FRIED GREEN TOMATOES (4 servings)

6 large green tomatoes

Salt and pepper to taste

3/4 cup flour

2 eggs

1/2 cup milk

2 tablespoons oil

3/4 cup bread crumbs

6 tablespoons butter

2 tablespoons chopped fresh parsley

6 slices bacon, cooked

Cut tomatoes into 1/2-inch thick slices. Sprinkle with salt and pepper and coat with flour. Beat eggs with milk and oil. Dip tomato slices in egg mixture, wetting thoroughly. Coat with bread crumbs. Melt butter in a skillet. Add tomatoes and fry until lightly browned on both sides. Garnish with parsley and top with bacon. Green Tomato Relishes

These recipes for typically American salty and sweet green tomato relishes are adapted from an old "Fannie Farmer Boston Cooking School Cookbook." They are tasty homemade versions of the commercial pickles most people buy. SAVORY GREEN TOMATO RELISH (Makes 4 pints)

2 quarts chopped green tomatoes

3/4 cup salt

1 teaspoon black pepper

1 1/2 teaspoons mustard

1 1/2 teaspoons cinnamon

1/2 teaspoon allspice

1 1/2 teaspoons ground cloves

1/4 cup mustard seeds

1 quart cider vinegar

2 green or red bell peppers, sliced

1 onion, chopped

Combine tomatoes and salt in a stainless steel or enamel saucepan and let stand 24 hours. Drain and add black pepper, mustard, cinnamon, allspice, cloves, mustard seeds, vinegar, peppers and onion. Bring to a boil and cook 15 minutes. Pour into sterile jars. Store in refrigerator. SWEET GREEN TOMATO RELISH (Makes 4 pints)

2 quarts chopped green tomatoes

2 green bell peppers, chopped

2 cups chopped onion

1 pint vinegar

1/4 cup salt

3 cups sugar

1/2 cup pickling spice in a cheescloth bag

Combine tomatoes, peppers, onion, vinegar, salt, sugar and pickling spice in a saucepan. Bring to a boil. Reduce heat and simmer 30 minutes, stirring occasionally. Discard spice bag. Pour into sterile jars. Store in refrigerator. $/ SCALLOPED GREEN TOMATOES (4 servings)

1/2 teaspoon salt

1 tablespoon sugar

2 tablespoons bread crumbs or cracker crumbs

1 tablespoon flour

1 pound green tomatoes, sliced 1/3-inch thick

Butter for cookie sheet

1 tablespoon brown sugar

Combine salt, (white) sugar, crumbs and flour. Dip tomatoes into dry mixture. Place on a greased cookie sheet or jelly-roll pan and bake, covered, in a 400-degree oven for 10 minutes. Remove cover, turn tomatoes and sprinkle with brown sugar. Return to oven and brown. Tomatoes can be frozen on the cookie sheet or pan and then placed in plastic bags.Adapted from "An American Folklife Cookbook" by Joan Nathan (Schocken, 1984) PENNSYLVANIA DUTCH TOMATOES (4 to 6 servings)

4 to 5 large green tomatoes

Salt and pepper to taste

1/2 cup flour

4 to 6 tablespoons butter

2 tablespoons brown sugar

1 cup whipping cream

1 tablespoon chopped fresh parsley

Cut tomatoes into 1/2-inch thick slices. Sprinkle with salt and pepper. Dip slices in flour. In a 12-inch skillet melt butter, add tomato slices and saute' slowly until lightly browned, about 10 minutes. Sprinkle with half the brown sugar. Cook 3 to 4 minutes. Transfer to a heated serving dish. Add cream to skillet. Bring to a boil over high heat and boil 2 to 3 minutes or until cream thickens. Pour over tomatoes and sprinkle with parsley. Adapted from "The Time-Life International Cookbook" (Holt, Rinehart and Winston, 1977) GREEN TOMATO FRITTATA (6 servings)

In her book "Cooking at Cooktique" (Doubleday, 1984), cooking teacher Sylvia Lehrer reprints the recipe for an omelet filled with green tomatoes that she got from fellow cooking teacher Giuliano Bugialli. But she makes an important substitution -- of wheat germ for flour -- that gives the filling a crisp texture and boosts the nutritional value of the dish.

4 large or 6 medium green tomatoes

1/2 cup plus 1 tablespoon olive oil

1 cup wheat germ

Salt and pepper to taste

6 eggs

Cut tomatoes into 1/2-inch slices. Heat the 1/2 cup oil in a 10-inch skillet. Coat tomatoes with wheat germ. Place only as many tomato slices as fit in a single layer in the skillet. Saute' until golden on both sides. Drain on paper towels and sprinkle with salt and pepper. Fry remaining tomatoes.

Beat eggs lightly with a pinch of salt. Heat remaining oil in an omelet pan. Add tomato slices and pour eggs over all. When eggs are well set and frittata is well detached from the bottom of the pan, place a plate face down over pan. Reverse pan and turn out frittata. Return pan to heat and carefully slide frittata into pan to cook other side. After 1 minute, reverse frittata onto a serving dish. Serve hot or at room temperature. PASTA WITH GREEN TOMATOES (4 to 6 servings)

In his recent book, written with cardiologist Richard Wolff, talented cook and artist Edward Giobbi outlines ways to turn high-calorie and fat-laden Italian specialties into still-delicious diet dishes. There are two green tomato pasta recipes and one for fried green tomatoes in "Eat Right, Eat Well -- The Italian Way" (Knopf, 1985), and like the other recipes in the book, they are followed by a breakdown of their calorie, cholesterol, fat, carbohydrate and protein content. This pasta dish, so useful for cooks stuck with an excess of green tomatoes, contains a total of 2,770 calories, 36 mg. cholesterol, 453.8 gm. carbohydrates and 72.3 gm. fat.

3 tablespoons olive oil

3 teaspoons safflower oil

1 medium onion, finely chopped

1 teaspoon finely chopped garlic

4 large green tomatoes, thinly sliced (about 8 cups)

2 tablespoons finely chopped Italian parsley

3 tablespoons coarsely chopped fresh basil

1/2 to 1 cup chicken or beef stock

Salt and pepper to taste

1 pound bucatini pasta (or linguine)

6 tablespoons parmesan cheese

Heat the oils in a medium saucepan. Add onion and simmer over moderate heat until it begins to brown. Add garlic, simmer 1 minute and add tomatoes. Cover and simmer 5 minutes. Add parsley, basil, 1/2 cup stock, salt and pepper. Cover and simmer, adding more stock if sauce becomes too dry, for 30 minutes. When tomatoes are nearly done, cook pasta al dente. Drain well and toss with sauce. Add cheese, mix and serve immediately.