At Quinn's Hardware in the heart of this historic city, seeds for a backyard vegetable garden still are sold by the pound from large bins, as well as in the tiny packages more familiar to Washington gardeners.

Parking is 10 cents an hour at a downtown meter, or $1.25 for a full day at the municipal garage. And in a restaurant along Market Street, the city's main thoroughfare, lunch, dessert and coffee come to $1.40.

But the small-town way of life still evident in many ways here gradually is disappearing as the City of Frederick and Frederick County are being drawn inexorably into Washington's suburban orbit.

Thanks largely to skyrocketing houseing prices in the D.C. metropolitan area and recent sewer moratoria in Montgomery and Prince George's counties, Frederick is in the midst of a development boom that has made it one of Maryland's fastest-growing counties.

"Frederick County if going crazy-it's unbelievable the number of houses that have been put up in the past few years," said County Administrator James L. Bryan. "It seems as though one day you've got a vacant field, the next day there's a subdivision there and the next day it's full of people.

Despite a temporary lapse during the economic slump of 1974 and 1975, the county's population has risen from 84,000 in 1970 to more than 105,000 today. In the same period, new housing permits have gone from 446 to 1,127, according to Herbert E. Ramsburg, head of the county office of licensing and permits.

Commercial development also has flourished in the county with the opening of two large shopping centers, Francis Scott Key Mall and Frederick Towne Mall, and two smaller ones since 1972.

And in downtown Frederick, an aggressive redevelopment program is turning the historic district into what officials proudly promote as "the same type of living as Georgetown or Old Town Alexandria at a less hectic pace."

But for most new residents, the lure of Frederick has been not so much the slower pace as the lower cost of housing. Last year, the average price of a single-family house here was $55,000 compared with $77,600 for the Washington area. And a three-bedroom town house in Discovery, a James E. Cafritx planned community, sold for about $40,000.

Located 45 miles from both Washington and Baltimore, Frederick is attracking its new residents from the two metropolitan areas. Donald R. Date, a one-time Baltimorean who is now director of the county's department of economic and community development, noted that, while he roots for the Colts, his neighbor is a Redskin fan.

Date said the majority of Frederick's new residents come from the Washington area, particularly Montgomery County.

Does this mean Frederick is going to become a bedroom community for Washington someday? "I think maybe we already have become one," laughed Date. "There are an awful lot of people going back and forth down that road (Interstate 270) every day."

According to Date, the actual number employed outside the county is about 30 percent of the current work force of 45,000. Besides using I-270, many commute by train from Brunswick, Md., located in the south-western corner of the county.

Date and other county officials see Frederick's development as a mixed blessing. On the one hand, they welcome the increase in the number of commuters living in Frederick because the higher salaries available in the Washington area mean more revenues for the county from Maryland's local piggyback tax on income.

Today, this piggyback tax is the county's fasterst-growing source of revnue, going from $3.5 million in 1975 to $8.9 million last year, according to County Comptroller Thomas M. Fox.

On the other hand, becoming part of Washington's suburban sprawl also has its disadvantages. And Frederick officials clearly are concerned, for example, over the prospect of the county becoming part of the Washington Standard Metropolitan Statistical Area (SMSA) in the 1980 census.

According to Date, they fear such a change might cost the county its status as a rural area in applying for federal assistance grants. They also are worried that becoming part of the Washington SMSA might discourage new businesses from locating in the county by forcing employers to adopt the higher wages that prevail in the D.C. metropolitan area.

Another disadvantage of development, as far as county officials are concerned, is that the influx of new residents is creating a demand for public services that far outpaces the county's ability to provide. Since 1970, the county budget has grown from $16 million to $46 million.

"A lot of newcomers say they like the rural atmosphere of the county but they want urban services," said county administrator Bryan. "One day they move in, and the next day they're up here asking for a new road of school. It's very difficult tokeep up with services when a county's growing as fast as we are."

Bryan's lament seems almost an understatement for a county that sill does not have its own police or fire departments. Instead, it must rely on Frederick City and Maryland State Police and on volunteer fire units for protection.

And the fact that current growth is scattered throughout the sprawling 664-square-mile county has exacerbated the problems of providing public services. Frederick County, for example, which is one of the few jurisdictions in Maryland with a rising school population, currently has a surplus of 200 spaces in its 344 schools, according to Lawrence Johnson, director of public services for the county. Yet 11 schools have been targeted as "overcrowded" because they are located in areas where heavy development has occurrd, Johnson added.

The areas where heavy development has taken place are located mostly in the south-eastern quadrant of the county and in pockets around the city. Johnson attributes this not only to the proximity of major roads but also to the availability of water and sewer facilities in these areas.

Not surprisingly, the pressures of development have led to rapidly escalating land costs in the county. A quarter-acre lot near the Montogery County line that sold for $3,000 in 1970 goes for as much as $18,000 today, said County Tax Assessor Glen H. Lenhart. The average cost of a lot throughout the county is between $15,000 and $20,000, Lenhart added.

In the heart of Frederick's historic district, increases in property values have been even more dramatic. Houses that sold for $16,000 to $20,000 in 1970 bring anyhwere from $60,000 to $120,000 today according to Frederick Mayor Ronald Young. To date 80 to 90 percent of the center city's housing stock has been renovated, Young added.

Results of restoriation efforts in the business community have been equally successfull. Ten years ago, this town-which was founded in 1945 and was the home of several historical figures, including Francis Scott Key, Barbara Fritchie and Thomas Johnson, Maryland's first governor-was severely blighted by abandoned buildings and massive knots of overhead electrical wires.

Since the inception in 1974 of Operation Town Action, an ambitious civic improvement program, however, 16 empty storefronts within a block of City Hall have been leased by new businesses. And, spurred by community pressure and local property tax incentrives, 150 businesses here have improved their buildings.

The offending electrical wires have been buried. Dozens of trees have been planted along Market and Patrick Streets. And, even more recently, a former vaudeville house has been restored as a performing arts center, the Weinberg Center for the Arts.

As further evidence of the significant changes taking place here, downtown Frederick now has restaurants featuring Japanese, Mexican, French and kosher cooking, in addition to the diners that remain as symbols of the past.

"I think the fact of that the county's growing is allowing this to happen in the city," conceded Young, who, at the moment, sees no end to it all. CAPTION: Picture 1, downtown Frederick, stretching north through the Ft. Detrick complex., Photos by Ken Feil-The Washington Post; Picture 2, New houses on the northern edge of the city.