It's the berries - raspberries, that is. Picking this crop is a family tradition in the Pacific Northwest

The shallow cardboard box is filling slowly - one handful of raspberries at a time. Connie Smith and her two sons aren't experienced berry pickers, but they bring enough enthusiasm to compensate for their lack of skill. The Smith family intends to pick exactly 12 pounds of berries - enough to make several batches of raspberry vinegar and some raspberry jam.

The Smiths are taking part in a Northwest tradition. Berry buyers can save cash by going into farmers' fields and picking their own.

``We do this every year,'' says Mrs. Smith. ``We just enjoy picking berries together as a family.''

``And we like eating them,'' adds nine-year-old Danny Smith as he pops a red raspberry into his mouth.

About 250 people a day venture into the fields at Love's Raspberry Resort, about 20 miles south of Seattle, although the ``U-Pick'' trade accounts for only a fraction of total sales. Like many of the farms in Puyallup Valley, Love's sells fresh berries by the ``flat'' - a large cardboard container holding about seven pounds - from a busy roadside stand.

But it's not only the locals who enjoy this fruit. The bulk of the nation's raspberries are grown here in the Pacific Northwest - on the western edge of Washington, Oregon, and British Columbia. The region's mild winters, temperate summers, and rich, fertile soil yield some of the world's best-tasting and most abundant berry crops.

A warm spring has brought raspberry season early this year. Unusually dry weather has kept the berries in superb condition - perfect for shipping to the East and Midwest.

In recent years, growers have rushed thousands of flats by air each July far from the berry fields to Chicago, Denver, New York, Washington, and other cities, where they fetch premium prices. Puyallup's Valley Packers Inc. has been shipping berries by air for six years. The berries are carefully packed in cellophane-wrapped baskets, placed in ice-cold, insulated containers, and sent on their way only hours after being picked.

``Our primary object is to get them on the shelves the next day in a very cool and salable condition,'' says Jim Johannes, the manager.

A missed airline connection means a lost shipment, says grower Dick Carkner.

``If it sits at O'Hare for a day in 100-degree heat - even in an insulated container - it's done.''

The fresh market requires a certain kind of berry: one that's picked just shy of full ripeness, that isn't more than a day or two off the bush, and that was harvested during dry weather, since rain often results in mold and rot.

The difficulty of meeting these conditions, combined with the general perishability of the soft berries, means that most of the crop ends up at processing plants. There the berries are frozen for later use.

Raspberries are currently a big item with consumers across the nation, thanks to a growing number of specialty fruit products. Frozen juice bars, ``fruit and cream'' bars, frozen yogurt, ice cream confections, salad dressings, seltzers, and several new juice blends all make use of Northwest raspberries.

``It's the fourth-hottest flavor in the country,'' says Dan Petek of the Washington Red Raspberry Commission. The impressive showing didn't come about entirely by accident. The commission, an agency funded by berry growers, has been lobbying food manufacturers to make greater use of raspberries. About 60 raspberry products have been unveiled in the past year.

Although the berries are usually far more costly than other fruits, Mr. Petek says the flavor is often sought out by consumers. ``If you don't have a red raspberry in the product mix,'' he notes, ``it's tough to keep the prices up.''

The popularity of raspberries is viewed with a certain degree of irony in the Puyallup Valley, where many farmers wonder how much longer they can make a profit growing them.

Among their biggest problems is getting the berries off the bush. In times past, the crops have been harvested by legions of pickers - often children getting their first taste of work. But despite pay increases that allow experienced pickers to make up to $50 a day, picking help is becoming progressively more scarce. The new immigration laws have further eroded the labor force.

Raspberry farmer Ted Picha is growing discouraged by the fluctuating number of pickers at his farm. On July 1, Mr. Picha had 60 pickers to help him harvest eight acres of raspberries. The next day, only 18 showed up, and Picha had to fill flats with berries himself.

``When you have to pick your own crop, it gets rather frustrating,'' he says. ``You never know from one day to the next where you stand.''

Picha's neighbor, Dick Carkner, who raises about 15 acres of raspberries, says new paper work and regulations - such as installing running water in the fields for pickers - are also placing a big burden on small growers.

``As much romance as there is in agriculture,'' he says, ``farmers are basically businessmen. If it becomes unprofitable to grow raspberries, they'll get out.''

Picha comments, ``Puyallup's berry industry is further threatened by encroaching development, which has already swallowed up a number of farms.

``Apartments, condos, and industry are eating up the land. If things don't turn around, this ground will be used that way, too.''

Despite the disappearance of berry farms in Puyallup, the amount of land devoted to raspberries in the Northwest is on the rise.

New acres are being planted in Canada and the northern part of Washington State, where land is less expensive. The newer farms are also set up for mechanical harvesting, which helps compensate for the shortage of pickers.

Among those who hope to preserve at least some of the Puyallup Valley's farmland with its U-Pick fields and berry stands is Picha's son, Russ. He intends to continue working the farm begun by his grandfather at the turn of the century.

Nevertheless, the younger Picha has taken a full-time job as a junior high school science teacher, and will be only a part-time berry farmer.

``I don't want to make farming my livelihood,'' he said. ``I'm not sure there's a future in it.'' Raspberry Vinegar 3 quarts raspberries 1 quart white wine vinegar 1 tablespoon sugar (or to taste)

In stainless steel bowl, add enough sugar to vinegar to counteract some of its bite. Add 1 quart raspberries and let sit for 24 hours.

Strain berries from vinegar, reserving vinegar. Put vinegar back in stainless steel bowl and add 1 quart raspberries. Let sit for 24 hours, then strain and add the third quart of berries.

After 24 hours, store in tightly sealed bottle and use in vinaigrettes. Goes especially well with salads that contain fruit. Raspberry Pie 4 cups raspberries 1/4 cup water 7/8 cup sugar 3 tablespoons cornstarch 3 tablespoons water Baked piecrust Whipped cream

Bring 2 cups berries, water, and sugar to boil over low heat. Mix cornstarch and 3 tablespoons water in small bowl add to boiling berry mixture. Take mixture off heat as soon as it clears. Cool. Add remaining 2 cups berries to mixture and pour into baked pie shell. Chill. Serve with whipped cream.

Jerilyn Brusseau's raspberry shortcake is a specialty of Brusseau's restaurant in Edmonds, Wash. Raspberry Shortcake 2 cups all-purpose flour 1/4 cup sugar 1/8 teaspoon salt 4 ounces butter 3 teaspoons baking powder 1 egg, lightly beaten 1/2 cup buttermilk 4 cups fresh raspberries, picked over 1/2 cup sugar 1 cup whipping cream Confectioners' sugar 1/2 teaspoon vanilla (optional) Mint leaves (optional)

In mixer at low speed, add first five ingredients in bowl. Mix until butter is size of small peas. Add beaten egg and buttermilk to mixture. Mix by hand until just blended. Add more buttermilk if mixture feels too dry. Do not overmix.

Place dough on floured board and shape into a ball. Flatten to about 7 inches in diameter. Use quick motions to shape so dough does not toughen. Cut dough with very sharp knife into quarters. Place pieces on small cookie sheet and bake at 350 degrees F. for 15 to 20 minutes, or until golden brown. Cool.

Place raspberries in bowl, top with sugar, and gently mix with spoon. Let stand one hour. Whip one cup medium cream, adding confectioners' sugar to taste when desired consistency is reached. Add 1/2 teaspoon vanilla, if desired. Cut shortcake wedges in half. Spoon raspberry sauce on bottom half of shortcake. Place top on berries. Top with whipped cream and fresh mint leaf. Serves 4.