Landscaping is expensive these days. Ask the Virginia Department of Highways and Transportation. It is spending $1.2 million to beautify a four-mile stretch of Shirley Highway leading into the District of Columbia.

A segment of the project - within a mile north and south of Army-Navy Drive - has been completed and features in part, 45 flowering trees, 47 Austrian pines, 94 Scotch pines, 370 red twig dogwoods, 17 pounds of crown vetch and 80,900 square feet of wood chips. It cost $182,000.

The money for the landscaping project, one of the most expensie in department history, comes from the federal highway trust fund, which provides aid to highway programs and is supported by taxes from highway users.

Davis Brothers Nursery in Rose Hill, Va. handled the first mile of Shirley Highway. Paul Davis, one of the owners of the nursery, said highway landscaping "is a large part of our business now. It's 50 perdent of our business."

Davis, whose nursery has completed highway, landscaping projects in Kentucky and Tennessee as well as Virginia, attributes the boom in highway landscaping to Lady Bird Johnson's efforts to beautify the nation's highways. "It's a nice thing to do, I think," he said.

Highway officials agree. "In recent years, we have been emphasizing even more the beautifucation of major highways leading to urban areas," said Al Coates, a highway department spokesman. He said similar landscaping projects are planned for the Richmond and Norfork areas.

Stat officials said the landscaping projects are expensive but justified.

Phil. Shaw, a landscaping architect for the state highway department, said the Shieley Highway project cost so much because of "a combination of factors. Trees are getting more expensive. The local labor force is high."

He said most contractors hire workers from the D.C. area, where wages are higher than elsewhere in Virginia.

Shaw said the landscaping is costly also because there are more risks and responsibilities for the contractors. They have to replace any trees or shrubs that dies within two years after initial plantings. The contractors also are responsible for watering, weeding and pruning during the two year period.

Robert I. Hundley, an envoirnmental quality engineer for the state highway department, said landscape contractors have tried to plant trees and shrubs that are less suceptible to heat and pollution on highways.

Hardwood trees and white pines are "fairly susceptible" to pollution and the departmenhas tried not to have many of those planted. "We've learned by experience," Shaw said.

Some plants along Shirley Highway are dying and will be replaced by the contractors this fall, he said.

"Some plants and some trees do die," said Hundley. But he said there has been "no tremendous loss."

The landscapong project completed by Davis Nursery also includes six zelkova [shade trees], 186 golden bamboo,351 border forsythia, 511 weeping forsythia, 525 tall hedge, 100 cherry laurel, 500 Fraser photinia and 7,727 Hidcote St. John's-wort.

Highway officials expect the last tow projects of the $1.2 million landscaping program, which extends form the 14th Street Bridge to the Arlington-Fairfax line, to be done in the fall and next spring.