Ruth Davenport craves broccoli right from the field, with heads so tight and emerald green they look like a tree-covered hill viewed from an airplane at 10,000 feet. Davenport, a regular customer at the Thursday afternoon farmers market at the National Bureau of Standards complex in Gaithersburg, bought a few heads one week and came back to offer her review the next.

"I thought it was marvelous," said the white-haired calibration specialist, still wearing her pale blue NBS lab coat.

Davenport buys bags of fresh locally grown corn, tomatoes and cucumbers each week from the handful of Montgomery County farmers who back their pickups and vans into parking lot 235 at NBS. Like people all over Montgomery and Prince Georges counties, she's taking advantage of the local harvest now overflowing from farmers markets and stands in the Maryland suburbs.

This summer's crops are abundant, according to growers and extension agents. Tomatoes are hanging like grapes on the vine. Berries are peaking. Squash is going for a song. Silver queen corn is ripening faster than farmers can pick.

And now, as the harvest reaches its stride, prices are dropping. Tomatoes average 59 cents a pound, and sweet corn is going anywhere from $1.50 to $2 a dozen. The cornucopia's contents are spread out at markets and stands at various times and places, with the main county-sponsored events held on Saturday mornings.

By 9 a.m. on Saturdays, the connoisseurs and bargain hunters have stripped corn and tomatoes from the county farmers market at the Silver Spring Armory on Fenton Street.

The best vegetables are gone from the wooden booths at the independently operated Montgomery Farm Woman's Cooperative on Wisconsin Avenue in Bethesda by 9:30.

By about the same time over in Prince George's County, at the Wells-Linson swimming pool complex, 5211 Calvert Rd., College Park, shoppers already have emptied most of the produce from the nine trucks that arrive there in the Saturday morning half light and whose operators sell until noon. The College Park sale is the only county-sponsored market in Prince George's.

And on individually operated stands stretching from Montgomery County's Butler Orchards north of Gaithersburg to a string of three truck farms along Piscataway Road south of Clinton in Prince George's, farmers are offering bushel baskets of beans and beets and summer squash and enough sweet corn to keep the Jolly Green Giant smiling all summer. The Allnutt farm in Sugarland west of Seneca has 3,000 cantaloupe plants ready to ripen with the next rain.

County officials don't even try to keep track of the farmers who lower pickup tailgates to sell a few pecks of produce along the roadside.

"The demand is there for fresh produce, homegrown rather than the supermarket produce that comes from Florida or California or wherever," said Rene Johnson, an agriculture planning specialist in Montgomery County.

Johnson helped organize the county-sponsored markets. In addition to the Silver Spring operation, begun five years ago, Johnson has helped arrange another market on Tuesdays from 3:30 to 5:30 p.m. at the National Institutes of Health parking lot 41-B and the Thursday affair at the same time at the National Bureau of Standards.

Quality standards are strict at both the Silver Spring and College Park markets. The farmers police each other to make sure they all live up to the "homegrown" label. In the official Montgomery County markets, growers must produce at least 50 percent of what they sell; in the Prince George's counterpart at College Park, vendors must grow at least 70 percent of the produce on their stands. But in both instances, all produce must come from local sources.

"We have a lot of hucksters trying to break in," said Bill Polen, a retired government computer specialist who sells produce grown on his Potomac farm at the Silver Spring market. "We had a guy come in with shrimp he claimed he got out of Rock Creek."

On a good day, the Polens can sell between $100 and $150 in fresh vegetables at the Silver Spring market.

It's strictly a family affair. Their son Bill Jr., 24, oversees the small farming operation and used to take the lion's share of the summer's profits (which can amount to nearly $3,000) to help pay his way through Georgetown Medical School. Daughters Debbie and Sharon cultivate the family's three acres of vegetables on Albermyrtle Road, pick the weekly yield and sell it at the farmers markets and from a small stand in their grandmother's driveway. The summer's profits now provide spending money while they're away at James Madison University. Bill Sr. and his wife Mary Ellen do most of the selling at the farmers market.

"Mom and Dad get nothing," said the elder Polen, who looked the part of a farmer with his gray stubble beard and "Drydene" auto parts hat.

For the Polens, the farmers market is a part-time venture and a financial supplement. For the Clines of Damascus, the two days a week they sell vegetables at the Bethesda farm woman's cooperative market is a tradition.

Esther Cline, who died this spring, was the family matriarch who started hauling the produce to the Bethesda market when it started in a tent during the Depression. Now her sons Robert and Lee work the 40 acres north of Damascus, and Lee's wife Lois sells fresh vegetables and fruit from the wood and glass booth every Wednesday and Saturday morning.

The Clines' market operation may not make it to the third generation. The weekly take barely pays the farm's taxes, and the Cline children are heading for big city life.

"My two kids are going the other way," said Lee, a lab technician at the National Institutes of Health. "They're not really interested in the farm. I guess it's just changing times. I don't know how much longer we can stay in it."

In sharp contrast, the local vegetable market has given new life to the Miller family farm on Piscataway Road south of Rte. 5 in Prince George's County. The farm has been in the family since the first Henry Miller sailed from Germany in the mid-1800s, stopped in Baltimore for a year, and bought the 300 flat, rocky acres to root the family.

Over the years, the farm's crops changed from grain to tobacco, according to Philip Miller, whose great-grandfather came from the old country. Now the mainstay is becoming a variety of vegetable crops. Four years ago, the Millers planted 15 acres in vegetables. A year later it was 40, then 125; this year the family has 200 acres of everything from cabbage and beets to strawberries and corn.

Philip, 28, drives a white Trans-Am with "U-PICK" license plates and runs the vegetable end of the farming operation, which is rivalling tobacco as the chief cash crop. The majority of the vegetable harvest is sold at the farm, through the stand or on a "pick-your-own" basis, but Philip trucks some of his bounty to the farmers market in College Park every Saturday. On a good day at the market, he can take in more than $1,000, he said.

"It's great," he said under the shade of his farm stand on a recent 95-degree Sunday afternoon. "The nicest people in the world come there to buy."