Out where the roads stretch past the suburbs and vegetable stands line the rights of way, hand lettered signs announce the local phenomenon: 'Silver Queen."

The high sugar, white kernel, corn, first planted in the Washington area about five years ago, has quickly outpaced all other varieties sold along roadsides and at local produce stands.

"We might as well throw away the yellow corn and all the other corns and grow just Silver Queen," said George Butler ob Butler's orchard near Damascas in upper Montgomery County. Butler expects to market some 84,000 ears of Silver Queen corn from his produce stand this season. Until about five years ago, he didn't even grow it," he said.

Since then, the all-white ears with even rows and characteristically sweet, firm kernels have come to dominate the market for fresh local corn, according to agricultural agents in Montgomery and Prince George's counties.

"It's become, by far, the number one sweet corn," said Richard Biggs, a horticulture agent in Montgomery County.

The evidence is at the roadside stands and even in some supermarkets that advertise Silver Queen by name.

At the Prince George's County farmers' market in College Park, growers sold about 500 dozen ears of the popular variety in 4 1/2 hours yesterday morning.

County agents estimate that commercial growers and weekend farmers grow more than 600 acres of Silver Queen in the two predominantly urban Maryland counties. It is grown here only for the local produce market, not for processing or shipping.

"Those who have a sweet tooth, for corn on the cob, they like that Silver Queen," said David Conrad, a Prince George's county agent.

Experts agree the reason for the corn's rapidly growing popularity is its extraordinary sweetness.

"It has the highest sugar content of just about any corn available," said Biggs. And the sugar doesn't change to starch as quickly as it does in some other varieties of corn, he said. That means the corn retains its sweetness longer, both on and off the stalk.

The corn was developed in the early 1960s by Frank Blankenburg, former director of sweet corn research for Rogers Brothers Seed Co. of Idaho Falls, Idaho.

Joseph J. Steinke, a Rutgers University horticulturist, said the corn's popularity spread by word of mouth, rather than through any elaborate marketing campaign.

It has become the "main-selling sweet corn from south Jersey all the way to Florida," he said.

To take over in this area, Silver Queen had to overcome a regional prejudice against white corn.

"Washington was a yellow corn market years ago," said Butler, the Damascus grower. But he said he's thinking about not bothering to plant the yellow varieties anymore.