It began just after dawn with picking tomatoes, what looked like trillions of them. It moved on to weeding and harvesting green beans and melons, and it ended with eggplants and red raspberries as merciful dusk set in.

The process would repeat itself tomorrow, but for now another day was done at the Wheatland Vegetable Farms, which otherwise cries to be called something like Dr. Planck's Outdoor College of Horticulture and Getting Things Together.

For more than one reason, this 60-acre spread in Loudoun County, owned and operated by Chip and Susan Planck and their children Charles and Nina, is one of the Washington area's most unusual farms.

It is unusual because the Plancks, who gave up the reasonable comfort of a life in academia to become farmers, in less than 10 years have turned their place into a profitable business that puts fresh fruit and vegetables on hundreds of metropolitan dinner tables.

It is more unusual because of its college-age work force, an odd collection of young people, mostly from affluent families and tony liberal arts schools, who subject themselves to long hours of hard labor and low pay for the chance to work alongside the Plancks, who remain teachers as much as farmers.

At the Plancks' knee, they learn how to hoe a weed and how to identify a ripe melon. They are forced to fend for themselves in intentionally spartan accommodations. They learn to endure the barbs and darts of demanding bosses. To learn how retailing works, they tag along with the Plancks to 11 farmers' markets each week around the metropolitan area. And, above all, they learn the meaning of work.

Of course, without these workers, most of whom don't return for a second season, the Plancks' ability to succeed in risky, labor-intensive agriculture would be limited. But the Plancks' bottom line is not exactly the same as that of the large-scale commercial farmer.

Susan Planck, standing on the edge of a field where student pickers stooped over long rows of Blue Lake green beans, put it this way: "Most of the people who come here have never been told what to do. What they learn here is how to use their time and how to be productive. They get no sense of productivity in college -- here, it is part of the daily rhythm.

"By this time of year we see the results of what we're doing, and it is pleasing. You see how much each of them has learned. We think we're teaching about work and productivity more than we're teaching about picking beans."

Chip Planck added, "You could take them in hand {and coddle them} or follow this model, which is our own. They leave a light on all day, I'm not going to replace the bulb. They need a Band-Aid, we provide one, but with the admonition that adults care for themselves . . . . These kids learn from each other. They have adjustment problems, but we give them a place to get their act together."

This year's crew of 11 field hands comes from such disparate places as Yale University, Earlham College (where the Plancks' son is a junior), Oberlin College, St. John's College in Annapolis, Cornell University and Kalamazoo Valley College. Hands, warned well in advance of inauspicious accommodations, long hours and low pay, are hired after completing lengthy application forms that require some essay-type answers.

"Typically we get people with no background and no future in this, yet some who have worked here have continued in farming," Chip Planck said. "We get kids who are environmentally oriented, interested in food. You see from the applicants' forms that part of their vision of the future is to be able to care for themselves a bit . . . . When they come with a low level of skills, I can show them a new world."

The Plancks' efforts show up in various ways.

Andrew Singer, a senior art and art history major at Cornell, was quickly stripped of illusions when he showed up in June. The Plancks put him to work unloading 250 bales of hay that would mulch tomato plants.

"I had this semiromantic illusion about farming. I heard about this place from a friend who worked here last year and I wanted to check it out," Singer said. "This summer made me realize that painting and drawing is what I really want to do. But more important, the Plancks and their experience have shown me that if you really want to do something, you can.

"The neatest aspect of this, more for them than for me, is that you think farming is the simple life. But it's 10 times more complicated than the average stockbroker's life."

Stacy Grimes, a St. John's sophomore from Westminster, Md., had a similar reaction. "Sitting in school and reading for nine months made me want to do something physical. But it was shocking when I got here. It was so much work and it was constant work."

Grimes, like the other field hands, worked about 63 hours last week, at $2.50 an hour. She had one day off; the other six began around 6:30 a.m. and several did not end until after dark. She shared cooking and cleanup duties and helped run the Plancks' stand at several farmers' markets.

"It's really neat what the Plancks are doing. It's a business, but they're doing what they like to do . . . . I've thought I would like to have an herb farm -- it's a vague idea, but it's one of my top vague ideas," Grimes said.

The student work force has been a vital element in the Plancks' success at Wheatland, where they began farming full time in 1979. After six years of teaching political science at the State University of New York in Buffalo, Planck decided he really wanted to farm.

He gave up his tenured position in 1973 and moved with Susan and the children to Loudoun County to begin an apprenticeship with the late Tony Newcomb and his wife Hiu, who operated the Potomac Vegetable Farms. The Plancks moved out on their own after five years and got through the first year with student recruits, an idea they lifted from the Newcombs.

They lost money that first year, but have turned a profit each year since, in large part because of the regional farmers' market network that got under way on a big scale in Virginia in 1980. The Plancks, their children and the student workers take Wheatland produce to 11 markets each week in Virginia, Maryland and the District of Columbia.

The star students of the Planck operation are Charles, 20, and Nina, 16, who take turns directing the visiting workers, managing markets, overseeing harvest and loading, and joining their parents in the teaching mission.

"They are completely academic, middle-class college students who want to 'do something,' whether it's having a mellow farm experience or getting their hands dirty," said Nina, a junior at Loudoun Valley High School. "I occasionally have to correct them or show them how to do a job. But there is no resentment -- everyone is responsive to criticism."

The elder Plancks, assiduous promoters of the grower-operated direct sales markets, played key roles in the opening of markets in Takoma Park, Manassas and just last month in Sterling. They spend spare time pushing the idea of an association of farmers that could open new markets in areas where consumers want locally grown fruits and vegetables.

Their own vision of place and purpose fits neatly into the concept of more small-scale local farmers feeding the metropolitan area, more people on the land, more families hanging together.

"I'm grateful we've had a business our children could be a part of," Susan Planck said. "It seems as though there aren't opportunities for kids to feel they are a part of the economy . . . . There should be more farmers because all kids would be working. You know, people keep talking about what we're doing as something new. But actually what we do is traditional agriculture . . . . It would be nice if kids from the age of 7 on could feel they were contributing to family or community. This is one of the ways."

By then, dusk was drawing nigh. She turned and jogged down a long dirt lane toward the trucks, where Dr. Planck's class of 1987 was loading produce for the next day's markets.