NATURE'S FIRST HERALD of spring isn't a daffodil or even a crocus. It's the silent flow of sap deep within sugar maple trees. Right about now, when the days begin to warm but the nighttime temperatures are below freezing, the sap begins to rise to nourish the new leaf buds. And that means it's sugarin' time.

The Indians were old hands at making maple syrup and used it to barter with settlers, for whom maple syrup and honey were the only available sweeteners. Once they got the hang of it, pioneer families welcomed an excuse for some outdoor activity after being confined indoors throughout the long winter. The whole family would camp out at the snow-covered sugar shed in the midst of their maple grove and harvest the sweet sap. The expedition was more frolic than labor and there were lots of chores for children to do.

From now until April you can capture much of the festive air of sugaring -- without the work -- at maple sugar festivals within driving distance of Washington. You can see demonstrations of tree tapping, collecting and boiling sap, and packaging the syrup. And, of course, you can enjoy munching treats from pancakes slathered with syrup to maple-flavored cookies.

For more than a quarter of a century, one of the major maple expositions has been the annual Monterey Maple Festival held in March in Highland County, Virginia's "Little Switzerland." Depending on the weather, the festival draws up to 20,000 people a weekend to this small town of less than 500. At this year's festival -- March 16/17 and 23/24 -- four nearby commercial sugar camps will be open from 8 to 6 so you can observe the entire maple syrup process, from tree to treacle.

Two of the camps, Vance Sugar Camp and Eagle's Sugar Camp, demonstrate the traditional method of boiling down the sap in cast-iron kettles. The Rexroad Camp uses long plastic tubing to bring the sap from the tree to the sugar shed, where it's boiled in large, six-foot open flat pans. At the Puffenbarger Sugar Camp, a vacuum pump draws the sap from the trees, much as a milking machine works in a dairy barn, and an oil- fired evaporator boils down the sap.

Local restaurants and county schools ply visitors with pancakes and maple syrup from 7 a.m. to dusk. Pearl McCray, a locally renowned cook, works out of the Highland Primary School, making sourdough buckwheat batter by the drumful to feed the line of waiting visitors. She also makes delicious sweet buckwheat batter. (Mother Nature, in her infinite wisdom, arranged for the geographic distribution of the sugar maple tree to be essentially the same as the buckwheat plant, making maple syrup and buckwheat cakes a natural combination.)

Everywhere in Monterey, you can buy maple-flavored cookies, maple-sweetened breads and a supply of maple syrup or maple sugar to take home. There's also a craft show with more than 100 exhibitors set up in the local schools.

A more flamboyant affair is the Pennsylvania Maple Festival in Meyersdale. This year's event, the 38th, will be held March 23 and 24 and March 27 to 31. Here the collection of sap and the processing of the syrup almost become a sideline to the celebrating.

Among the festivities: coronation of the maple queen; presentations of a historical pageant; a parade through downtown; local craft and quilting shows; an outdoor stage with entertainment by cloggers, bluegrass bands and country music performers; a horsepulling contest; two car shows of antique and modern classics -- and plenty of pancakes and maple syrup at the Lions Club, American Legion and fire house.

Festival Park, near the center of town, is the center of activity and the home of Maple Manor and Museum. There'll be tours through the antique-filled 200-year-old house, and in the museum you can learn how little maple sugaring has changed since the colonists introduced the iron pot for boiling the sap. Now, as then, the finest sugar maple trees, at least 10 inches in diameter, are selected to be tapped. On the sunny side of the trees, about four feet above the base, a half-inch hole is drilled to a depth of three inches, and a metal spout, or spile, is inserted to keep the hole open and drain the sap into a metal bucket.

There's nothing more to do but wait for the steady drip, drip, drip of the crystal-clear maple sap. While the yield from each tap varies greatly, the average is ten to fifteen gallons per season. The sugary sap has to be collected every two or three days and boiled down in large cast-iron kettles over wood fires to prevent its spoiling.

This is where the real work starts. Since the sap averages two percent sugar, 40 gallons of sap must be boiled down to produce one gallon of maple syrup. And since it requires about one cord of wood to boil down twenty gallons of syrup, the woodchopper is pivotal to this operation.

The boiling goes on day and night to remove the water in the sap, rid it of tannin and other impurities and also chemically convert the various sugars in the sap into triose sugars, which give the syrup its characteristic color and flavor. While still hot, the syrup is filtered through cloth, packaged and sealed to prevent spoilage.

The first sap collected in the season yields a pure white sugar that's hardened into blocks and saved for special candy or cake making. Each successive run of sap becomes darker and makes varying qualities of "soft sugar," then syrup, then maple-molasses. After about three weeks the maple leaf buds begin to open, the sap changes in character and sugaring is over until next year.

HOW SWEET IT IS

Sugaring is the kind of late-winter sport anyone can enjoy. All you need is transportation and a sweet tooth to enjoy these maple syrup events. With the recent unseasonable weather, it's probably a good idea to call ahead to confirm dates.

MONTEREY MAPLE FESTIVAL -- March 16/17 & 23/24, in Monterey, Highland County, Virginia. This two-weekend festival runs from 7 to 6 each day; the sugar camps open up around 8. To get there, take I-66 west to south on I-81 to Staunton. Take scenic Route 250 west for 43 miles to Monterey. 703/468-2550.

PENNSYLVANIA MAPLE FESTIVAL -- Meyersdale, Pennsylvania. March 23/24 & March 27-31. This is the biggest and most elaborate maple festival in the area. The Craft Show is open 10 to 5 each day; the historical pageant is presented both Saturdays at 2 and Wednesday at 10 and 2; the horsepulling contest is at 1 on March 24; and the parade is at 5 on March 30. Admission to Festival Park is $3 adults, $2 senior citizens and children 13 to 17, children under 13 are admitted free. Separate charges for the pageant and meals. Pancakes and sausages, along with other food, are served 9 to 6. To get there, take I-70 west to Hancock, Maryland. Continue west on U.S. 40 beyond Frostburg to Exit 22. Take U.S. 219 north for 12 miles to Meyersdale. 814/634-0213. If you can't wait till the middle of the month to wrap your mouth around some new maple syrup, here are some other area maple syrup events, starting next weekend.

A SUGARING CELEBRATION -- March 9, Neesing Nature Center in Stroudsburg, Pennsylvania. Demonstrations are given from 10 to 4. Call 717/992-7334 for information.

MAPLE SYRUP DEMONSTRATION -- March 9, Brookside Nature Center, 1400 Glenallen Ave., Wheaton. Demonstrations and taste testings for youngsters, at 11, 1 and 3. Rain date is March 10. 301/946-9071.

MAPLE SUGARING -- March 9, Hibernia County Park, Coatesville, Pennsylvania. Demonstration from 9 to 4; rain date is March 30. 215/431-6415. SUGARING DEMONSTRATIONS -- March 9, 10, 16 & 17, Cunningham Falls State Park, Thurmont, Maryland. Sugaring demonstrations from 10 to 4. 301/271-7574.

MAPLE SYRUP DEMONSTRATION -- March 16 & 23, Shaver's Creek Environmental Center, Penn State University, University Park, Pennsylvania. Demonstrations from 11 to 2. 814/238-5872.

MAPLE SYRUP DEMONSTRATION -- March 17, Goose Woods Sugar Shack, Moutour Preserve, Turbotville, Pennsylvania, 2 to 5. 717/437-3131.

MAPLE SYRUP DEMONSTRATION -- March 30/31, Bradys Run County Park, Fallston, Pennsylvania. 11 to 2. 412/728-5700.