Developers began work on a large Montgomery County project earlier this year by transplanting more than 200 trees, some more than 40 feet tall, from the site into a temporary nursery. When construction is complete, the trees will be replanted around the new office buildings and homes.

The work will cost an average of $400 a tree, less than buying and planting new trees on the site once occupied by the Washingtonian Country Club, according to Benjamin White Jr., a former Fairfax County "tree cop" who now has his own company specializing in tree preservation.

At the 620-acre Fair Lakes commercial and residential development in Fairfax County, the owners started work with a survey to identify trees that should be protected during construction, according to landscape architect Christopher B. Bogert. About 900 trees were preserved, noted Bogert, who said part of his job for the Hazel-Peterson Cos. is to "stand in front of the bulldozers."

Prodded by local regulations and a growing awareness that tree-shaded developments will bring more money, some companies are moving away from the once-common practice of bulldozing every green plant and tree to prepare for construction.

The idea of preserving vegetation "began catching on about three years ago," White said. "It's just the good developers who are doing it." He added, however, that there's still a lot of tree destruction because "it's cheaper in the short run."

Montgomery County makes its approval of developers' site plans contingent on preserving vegetation, according to Wynn Witthans, a Montgomery landscape architect.

County urban design department staff members inspect sites before grading begins to ensure that trees to be preserved are fenced off, she said, and when builders destroy vegetation before submitting site plans the county asks them to plant new trees.

County officials "were very encouraged" recently when the Spaulding & Slye development firm moved nearly 100 trees out of the way of buildings it is erecting in a Shady Grove office park, Witthans said. Workers lifted trees out of the ground with a massive tree spade, and lowered them into new holes. The largest was a 77,000-pound crab apple tree believed to be nearly 100 years old, according to a company official.

Fairfax County uses a landscaping ordinance and rezoning procedures to enforce tree preservation because the Virginia General Assembly has consistently refused to pass enabling legislation permitting stronger local laws, according to Douglas A. Petersen, an assistant county arborist. The landscaping ordinance requires preservation of vegetation needed to preserve soil and maintain clean water.

The 15 employes in the arborist's office review developers' building plans and inspect construction projects to ensure that property owners save trees whenever possible, particularly unusual types. County experts are currently urging a developer to preserve six large pecan trees, usually found only in the South, and expect to condition rezoning approval on an agreement to save the trees, Petersen said.

If a property owner plans to build the type of housing for which the land is already zoned, however, a builder "doesn't need anything from the county." It is still general practice, particularly among single-family home developers, to cut down everything, he said.

"A wooded lot sells much better and has more sales appeal than a barren lot" but most residential builders bulldoze subdivisions before they start construction, said Jeff Miskin, a horticulturist and president of Ace Tree Movers.

"There are a lot of factors that go into whether trees can be saved or not," said Stanley Halle, a Washington area builder and former head of the Suburban Maryland Building Industry Association. "It costs a lot more money to save trees ... from $1,000 to $2,000 more per lot. You have to do selective clearing" using chain saws instead of bulldozers.

Commercial developers are finding that trees make their projects more marketable, an important consideration in the Washington suburbs where 20 percent of the office space stands empty, according to several industry experts. Wooded and landscaped property sells and rents for higher prices than buildings standing on treeless grounds, they said.

"In an area as competitive as this market, you have to give the corporate user more," said Chip Ryan, a partner in Cambridge Development. "We've become more sophisticated as a company. Now we have a budget line item for landscape," he said, and hire professional landscape architects.

Most large developers set aside from 5 to 15 percent of their construction budgets for landscaping, according to one estimate.

It is easier and cheaper to preserve and build around trees already standing on a development site than to transplant them. Successful transplanting depends on several factors, including the tree's root system, the time of year and the size of the tree, according to Petersen. Moving trees with trunks more than eight inches in diameter gets "very risky," he said.

Arborists and tree movers have learned more about trees in recent years, however, and several of them said the survival rate has increased. Benjamin White said only trees with a 75 percent chance of being alive 10 years from now were moved on the Washingtonian Country Club property, and he said he expects that 90 percent of these will survive.

Although tree moving and preservation seems to pay off in the long run, it is costly. Moving large trees with a crane can cost $5,000 a tree or more, according to Miskin. Using specially designed tree movers is less expensive, and the largest of these -- mounted on a truck -- can move trees that are up to 40 feet tall, he said. Volume lowers the cost, too. "If we move a single tree it could be $700, or if there are more it could be as cheap as $100," Miskin said.