Most mornings, just before daylight, Bill Stalcup and his youngest son Dana, 20, fire up their Farmall-140 tractor and head for the checkerboard of vegetable plots they cultivate along Park and Kirby roads in Fairfax, County. By the time the sun is up, the Stalcups have made three or four stops, gathering tomatoes or corn or beets from the plots scattered among the tidy subdivisions of McLean's Chesterbrook neighborhood.

Then, before Old Dominion Road fills up the commuters, the Stalcups head for Sam Stalcup's vegetable stand in the Chesterbrook Shopping Center on Old Dominion near Kirby Road.

It's all in the family, and it has been ever since Inez Stalcup -- Bill and Sam Stalcup's mother -- began selling the family harvest at the Chesterbrook General Store about 50 years ago.

"This whole operation has been handed down over the generations," said Bill, who at 67 is a year younger than brother Sam.

Stalcup's one of 10 established stands in the area, according to county extension agents, and all must have a vendor's license to do business.

But if you sell only what you grow, no license is necessary, and Northern Virginia officials say they can't even begin to estimate how many pickup trucks overflowing with tomatoes and corn and potatoes line up along county roads when the harvest comes in each summer.

On any day of the week, though, as the local strawberry season gives way to summer squash and sweet corn, Northern Virginians are likely to find a roadside stand with "fresh from the fields" produce.

If it's Saturday, farmers from suburban Virginia and Maryland and even as far away as West Virginia are trucking their produce to a farmers' market at the Arlington Courthouse or to a similar affair at Market Square in Old Town Alexandria.

If it's Wednesday, some of the same growers are just about to lower their tailgates and set up business in front of the Massey Building in Fairfax County.

Other vendors operate six, or even seven, days a week out of stands that range from large, permanent structures to three-sided aluminum sheds, to the tailgates of battered pickup trucks.

Many offer vegetables and fruits only; others like Hall Kern's Reston Farm Market on Rte. 7, stock cheese, coffee, tea and even plants, in addition to the usual selection of fruits and vegetables.

Some farmers in the area, like Tony and Hiu Newcomb, who operate Potomac Farms on Rte. 7 west of Tysons' Corner, sell produce right at the edge of their fields, and also make deliveries to many of the small stands in the area. Most of the produce from Potomac Farms, the Newcombs are proud to point out, is organically grown.

Whatever the operation, most fruit and vegetable stand sellers try to offer produce from the area, although vendors at some of the larger stands admit that they stock produce from California and Florida.

Regardless of where the produce comes from, sellers contend that it is the freshest around, even though the prices tend to be a bit higher than in most of the bigger groceries.

At Sam Stalcup's stand, Silver Queen corn was selling at four ears for a dollar, while yellow corn at a Safeway in the shopping center was six ears for a dollar. String beans were 79 cents a pound both in the air-conditioned grocery aisles and under Stalcup's yellow umbrellas. Tomatoes from Montross, Va., were 85 cents a pound at Stalcup's, while "homegrown" tomatoes at the Safeway were 69 cents a pound. Texas cantaloupes were three for $1 at Stalcup's, 79 cents each at the Safeway.

"I think their prices are high," said Nancy Wright of Reston as she loaded up a bag of melons and corn at Stalcup's, "but I've always been satisfied."

For many local produce sellers, the season began in April, when the first pickings came in. But the bounty of the harvest is just now being reaped, as the same searing days and muggy nights that drive Washingtonians from the city create a great greenhouse for vegetables and fruits. Area sellers say this is one of the best seasons they have seen.

"This is perfect weather for corn," said Bill Stalcup, who owns a furniture store, where he works every day after his early morning harvest rounds.

This year's harvest, according to county agents, has helped the growing popularity of roadside stands and farmers' markets.

"People say the market here is just fantastic, and we hop to expand it," said Raj Waghray, a county extension agent in Fairfax who helps oversee the farmers' market at the Massey Building. The market, now in its second year, is open every Wednesday from 11 a.m. to 5 p.m. Anyone can sell produce there as long as the vegetables and fruits are homegrown. This year, Waghray estimates, the market has averaged about 25 stands every week, with farmers from all over Northern Virginia and one or two from Maryland.

The market in Old Town Alexandria operates under the same rules, but that Saturday affair starts early and ends quickly. The early shopper gets the corn, says Faith Simpson, a secretary with the extension service, and the late riser gets nothing.

"They start setting up at 5:30 a.m. and if you're not there by 9 or 10, everything's gone," she said.

Early and long hours are the rule for most produce sellers.

Sam Stalcup often gets up at 3 a.m. to look over the produce at the wholesale vegetable market in Northeast Washington, where some vendors shop, and he sometimes makes a second trip to restock later in the day. In early spring, before the local harvest has hit its peak, he relies on Southern and California produce to supplement food from nearby farms.

"I try to buy things the supermarkets don't have," Stalcup said. "They're forced to buy carloads of fruit and vegetables picked green, but I can get it in small lots that are of much better quality."

In addition to his main stand, Stalcup operates one mobile unit, where college and high school students earning the minimum wage work the stand.

Paul Varela, a student at Westeyan College in Connecticut, landed a job at the mobile unit. His place of business is a truck bed and cardboard boxes lining the curb.

In McLean recently, Varela was working in a neighborhood that had been the scene of frequent holdups, and was warned, he says, that sooner or later he might be robbed.

"But I don't really worry about it," Varela says with a grin. "I just think it would be embarrassing for a crook to have to hold up a fruit stand."

Stalcup also runs a stand in Georgetown, but says he relies more and more on the Northern Virginia market, where business is booming. "My best days, I make over $300 at each (virginia) stand," Stalcup says, "but I seldom hit $1,000."

Minnie Truitt, who owns Mrs. Beall's Outdoor Market in McLean, pooh-poohed Stalcup's claims of big takes. But, although she has been in the fruit stand business for 20 years, she isn't giving away any trade secrets about her income.

"I'd rather not go into all that," she responded to a question about her daily take. "I don't want the competition to know my business."

Truitt operates her market from late April until Halloween, and says she spends her winters watching soap operas and waiting for April.

"I can't wait for the spring," Truitt says. "I really enjoy the people. I've had the same customers all these years and now their grown-up children come around."

Truitt's stand consists of movable tables in a lean-to covered by awnings. Because of its somewhat temporary state, Mrs. Beall's Outdoor Market often falls victem to the weather.

"That's the trouble with outdoor fruit stands, you have to learn to put up with the weather. But my customers have learned to run with me when it starts raining," Truitt says with a laugh.

While Stalcup and Truitt emphasize the homegrown, basic vegetable, Hall Kern at the Reston Farm Market tends toward the exotic. Under the open barn at the junction of Rte. 7 and Rte. 606, Kern sells everything from live trout from a farm in Shenandoah to snake oil.

"This is kind of a gourmet farm market," said the 41-year-old Kern. "We try to stock the best of everything, even if it ocsts more."

Last year the market grossed $300,000, says Kern, who used to live behind the sign on the roof of the barn. "They started to call me mountain man," he said. "I finally broke down and moved into a house. It's not quite as nice, but at least there are no mosquitoes at night."

Live trout, swimming in a galvanized tank and $4 each. Every Friday, Kern smokes a few and sells them for the same price.

Double-yolk brown eggs are $2 a dozen. The herb vinegar is made by Dierdre La Rocque, who works at the counter. The sticky buns and pies and fat loaves of bread come from the Benders, a Mennonite family in Manassas.

The lemon-lime water in a cooler is free, but the homemade soda is a buck a bottle. The flavor depends on the season. In June, it was mulberries Kern and his helpers picked early one morning, then crushed to make the mulberry syrup that is the basis of the soda. This month, Kern expects the flavor to be peach from fruit grown is southern Virginia.

And if you're wondering what the best buys this month will be, take a tip from Kern and other fruit and vegetable vendors. Until about the 15th, green beans, squash and beets should be abundant. By the end of the month, locally grown tomatoes, sweet corn picked all over Northern Virginia and cantaloupes from the Eastern Shore should fill the stands.