Just over a month ago, the Rev. Laura L. Swett was in her office at Fairfax Christian Church when a man identifying himself as a certified arborist stopped by unexpectedly.

"He knocked on the door and said, 'I want to adopt your tree,' " Swett said.

The tree-care professional was Bill Beach of the Care of Trees. The tree he had his eye on is a copper beech that stands on the church's front lawn along Main Street in Fairfax City. Beach offered to care for it, free of charge.

"When you have a trained eye, you just can't help but see it when you walk down the street," said Beach, who said he first noticed the tree 13 years ago. He estimates that it is more than 200 years old.

From the copper beech in Fairfax City to the twin Canadian hemlocks at Scotts Run Nature Preserve in McLean to a 165-foot-tall pecan tree at Mount Vernon, Fairfax County boasts a number of majestic trees. Though development has wiped out acres and acres of trees, county foresters estimate Fairfax still has 50 million, covering 42 percent of the land area.

Because of the climate here, the county is home to about 130 of the 826 species of trees that grow in the United States -- an unusually high number, according to foresters.

"We're not exactly the southern climate, we're not exactly the northern climate, so you do get a mixture of species," said Ben Wharton, the county Park Authority's urban forestry crew supervisor.

Virginia is even more remarkable for its variety of trees compared with Europe, said Jeffrey L. Kirwan, an extension specialist at Virginia Tech, where he teaches forestry and keeps a database of the state's biggest trees.

The biggest tree of any species, called a champion tree, is catalogued at the local, state and national levels by various organizations. Each tree is awarded a number of points, based on height, trunk circumference and average crown spread.

The church's copper beech, at 354 points, is a state champion, for example. The highest point total in the country is 1,321 for the General Sherman giant sequoia in California, the world's largest living thing and probably more than 3,000 years old.

Kirwan emphasized that these horticultural treasures deserve respect.

"Trees connect us with our history," he said. "When you get back to 300 or 400 years old, [these trees] have been witnesses to every single event of our own . . . history."

Based on suggestions from state and county foresters, on these pages are a few of the county's champion trees.