IF YOU care a whit about herbs, the place to have been the day they dedicated the Herb Garden at the National Arboretum was not in the garden but in the tiny kitchen on the grounds where Carol Clark was putting the finishing touches to lunch. While Clark chopped up the mint, slice the pate, stirred up the soup she offered a wealth of useful hints about herbs, her cooking speciality.

But, of course, first you had to find the Arboretum, a Washington treasure so far off the beaten track, you have to want to go desperately (and own a car) to get there. The Arboretum, with 444 acres of land and water, is located near the Benning Road-New York Avenue intersection, but far enough from it that you could be in the Maryland countryside instead of beside a major car and truck route. As a research and educational center on trees and shrubs, it was a natural choice for the National Herb Garden, the gift of The Herb Society of America. The garden has been created at a time when there has been a resurgence of interest in things natural: naturally dyed fabrics, herbal teas, cooking with herbs.

Twenty years ago the only herbal tea most Americans knew anything about was camomile, and only Peter Rabbit drank that.

Knowledge of fresh herbs for cooking wasn't much more sophisticated. There was mint to put in tea and make into jelly, chives for sour cream on the baked potato, parsley for decoration. But most people thought sage, rosemary and thyme were quaint medieval substances that sounded nice in a song about Scarborough Fair.

Unless, of course, you happened to be part of an ethnically oriented family that used basil and oregano for tomato sauce; or mint with yogurt, or sorrel in soup.

Today dried herbs and spices and combinations thereof take up one section of a supermarket aisle. In season some markets offer fresh herbs (see related story) though the surest source of supply for them is still your own garden.

Which brings up another point: you don't need a garden, or even a patch of dirt to raise herbs. They do well in pots in a sunny location and some of them grow quite well indoors during winter.

Carol Clark does most of her herb growing in the summer, using several different methods for preserving them for winter use that produce better results than drying. Those were the secrets she shared, along with a firm conviction that everyone ought to use herbs in place of salt. "I'm on a low-salt crusade.American people have got to cut salt." Clark has high blood pressure so she uses no salt, but she has never been successful in her crusade with her husband. "I never salt enough for my husband." She uses summer savory and lemon juice in place of salt to season vegetables.

Clark, who teaches cooking in Reston, where she lives, says one of her student's favorites is a mixture she calls chop-chop. It's a herb base she freezes. It then can be used in soups, sauces, stews.Frozen herbs retain their flavor better than dried ones do.

She also preserves herbs by making herb butters, which are then frozen in small Dixie cups and used over meats, fish and poultry, and to make sauces.

Herb vinegars are another method of preservation Clark likes, but she warned that directions which call for boiling the vinegar and herbs "destroys the volatile oils and makes vinegars more acid. I don't know why they have those directions," Clark said. "Just put the vinegar and herbs in the sun." Then when they are ready, remove the old herbs and add some fresh ones for color and appearance.

Clark also preserves some herbs, such as basil, in layers of salt. The salt prevents discoloration. She washes off salt that clings to leaves before using them. Sometimes she preserves herbs in oil and sometimes she simply removes the leaves and throws them in a plastic bag, ties the bag and puts them in the freezer.

Frozen herbs will discolor as soon as they defrost, but their flavor is maintained.

If you already have a selection of herbs growing in your yard, don't forget that annual herbs such as basil, dill and summer savory will go to seed once they flower. So pick off the flowers and as you need leaves, strip them from the bottom.

If you want a simple, but informative book on growing herbs and using them, "A Cook's Guide to Growing Herbs, Greens & aromatics by Millie Owen (Knopf, $6.95) is useful.

Here are some of Carol Clark's recipes. CHOP-CHOP (fills 4 mini ice cube trays) 2 packages unflavored gelatin 1 cup water or chicken stock 6 cloves of garlic, peeled and chopped. 3 medium onions, peeled and chopped 1 bunch watercress 10 sprigs parsley Handful of fresh herbs of your choice 3 tablespoons fresh lemon juice

Soften the gelatin in the water; heat to dissolve. Cool. Cut off stems of watercress and parsley and discard. Place ingredients in a blender and blend until have a jade-green puree. Spoon mixture into sections of mini ice cube trays and freeze.

Add to sauces, soups, stews without defrosting. HOMEMADE SPICED CREAM CHEESE 8 ounces cream cheese 4 ounces farmer cheese 2 large cloves garlic Salt to taste 1/2 cup finely minced chives 1/2 cup finely minced parsley

Lots of freshly ground black pepper

Mash the garlic with salt in a mortar. Soften cheeses and mix with other ingredients. A ball of the cheese can be rolled in pepper or the pepper can be mixed in. HERBED POPOVERS 2 eggs 1 cup flour 1 teaspoon salt 1 cup milk 1 teaspoon dried sage 1 teaspoon dried chervil

Combine ingredients in a blender. Blend 1 minute. Pour into greased large-sized muffin pans, 2/3 full. Bake, at 450 degrees for 30 minutes. Reduce heat to 350 degrees and bake 15 minutes longer. Serve immediately with lots of sweet butter.

HERB BUTTERS -- 1/2 cup roughly chopped fresh herbs to 1/2 cup butter, few drops lemon juice or hot pepper sauce. For variation, add grated cheese. Freeze.

HERB VINEGARS -- Fill a jar with fresh herbs and pour in vinegar. Cover and allow to stand in warm place a week or two. Test after a week. When vinegar has taken on strong flavor of herbs, strain, replace old herbs with fresh herbs (it helps to identify the vinegar flavor), cover and use as needed. fGarlic or shallots are always a nice addition.

Use red wine vinegar for stronger herbs. Use rice vinegar for more delicately flavored herbs.

HERB OILS -- Made the same way as vinegars. For salads, use olive oil.

HERB MUSTARDS -- Combine enough white wine vinegar with dry mustard to make a paste. Add finely chopped herbs to taste along with minced garlic or grated horseradish. Add salt to taste.

HERB CHEESES -- Add your favorite combination of fresh herbs not only to cream cheese, but to cottage cheese. Mix herbs with grated cheddar cheese and enough butter and milk to make of spreading consistency.