LETTUCE HAS an ancient and noble history. Its ancestor, the compass plant, guided wanderers through the wastelands of the Middle East and provided them with thirst-quenching, if somewhat bitter, juices. Augustus Caesar, believing himself cured by a diet of lettuce when more formal medications had failed, is said to have erected a statue to this plant. Under cultivation since 500 B.C., lettuce can no longer be found in the wild but has developed nicely into several distinct types.

Loose-leafed lettuce is the fastest growing and the best to plant now in a Washington garden. Black-seeded Simpson and frilly Red Ruby are ready to eat in 45 days from sowing, Green Ice and Oakleaf varieties take a little longer to mature but are slower to bolt when hot weather hits in June. Butterhead is the fastest-growing headed lettuce and tastes wonderful even when picked early as thinnings. Bibb lettuce and its more heat-tolerant cousin, Buttercrunch, take 75 days from seed to loose, soft-leaved heads. There are salad greens galore, enough to suit almost every taste or growing place imaginable.

Longer-maturing types are best planted in late summer for a fall crop, or the luxury of picking your own in winter for a small investment in a cold-frame. Upright lettuce, Romaine or Cos, awards the gardener's 80-85-day wait with crisp, flavorful leaves. Brittle, crisp-headed lettuce like Great Lakes and Iceberg are the longest growers (90 days or so) but can withstand heat better than the softer varieties.

Garden cress is ready to eat within 10 days after planting and grows indoors as well as out. Watercress, found wild in shallow streams or springs, will tolerate a dank, shady spot in a city garden. In place of the difficult-to-grow Belgian endive you may choose instead Sugarhat Chicory for endivelike leaves without the fuss. For those who enjoy the flavor of celery, which is difficult to grow well in this area, try celtuce or lettuce on a celery-like stalk.

With Washington's notoriously short springs, the best way to grow an early salad garden is to plant several feet each of a variety of greens. You may need to lighten your soil a little with compost and sand, and fertilize frequently with nitrogen for good leaf growth. Watering with liquid manure or a green houseplant solution (fish emulsion is good) every week or two after seeds have sprouted will produce healthy, vitamin-rich salad crops. In damp weather you may be troubled with slugs or leaf rot. Tar-paper collars keep worms off any seedlings, or you can set out slug traps (jar lids filled with beer). Lettuce rot comes from the soil itself and can be avoided by spreading clean sand under each head of lettuce or rotating your crops annually.

To maximize crispness and preserve fragile vitamins, pick lettuce just before using. Wash carefully and dry in a salad basket or spinner. If you must store lettuce, place leaves in a clean dish towel and roll up gently or invest in one of those new cloth salad bags.

The best spring salad contains variety in color and texture. For dressing you may want to experiment a little with oils -- olive, safflower, peanut, corn or walnut. Wine vinegar or lemon juice adds tartness without excess acidity. A dash of sugar will cut sharpness in dressing, a pinch of mustard increases it. Never dress a salad until just before serving or the acid will wilt leaves as surely as heat will. GARDEN SALAD (4 servings) 1 quart container filled with freshly picked lettuce and greens (Ruby Red, Bib, Romaine and/or cress) Handful of fresh parsley Sliced radishes, fresh raw peas, or hulled sunflower seeds for added crunch 1/2 cup virgin olive oil 1/4 cup lemon juice 2 teaspoon prepared French mustard Freshly ground pepper and salt

Wash greens and parsley. Dry and break into bite-sized pieces, tossing into a salad bowl. Add garnishes if you like. Pour oil, lemon juice, mustard into a jar, adding pepper and salt to taste. Shake well and pour enough dressing over salad to barely coat the leaves when tossed.