It takes a tough woman to care for temperamental trees. In Alexandria's spring, when the March winds begin tearing and toppling the city's 18,000 trees, the city arborist rolls up her sleeves.

"Yes, exactly," says Jennifer Hollings, 51, Alexandria's official tree guardian. "It can be quite exciting." For two years she's clucked over the public trees full time. With her no-nonsense British outlook and her weathered, capable hands, she is the nanny of the arbors, the Mary Poppins of the maples and oaks.

"I'm not an environmentalist in the sense that I don't get mystical about them," she says of her charges. "But I can get rather upset if they're being mistreated." What with the watering, the pruning and the plying with pesticides, "it's a full-time job, and then some," Hollings says briskly.

On call for tree disasters day and night, she is worth, she says, every penny of the $20,000-plus the city pays her. And in suburban Washington, she is unique, the only one of her colleagues in public works departments around the Capital Beltway with trees alone to trouble her.

Now that it's spring, Hollings has put away the tree charts and maps she pores over during the winter. From now until autumn, 7 a.m. until after 4 p.m., she will be jolting around town in her white pickup truck, her eight-man tree crew at her command. She has already made her annual paint-bucket tour, daubing city curbs where her crews will leave the 360 saplings that will be planted this season.

Alexandria spends $60,000 a year on new trees; an average 400 a year die and have to be replaced. This year's selection reads like a dream menu for a gypsy moth: 100 Bradford pear, 25 red maple, 30 red oak, 10 willow oak, 10 Virginia cedar, 10 green ash, 16 golden rain trees, 10 maiden cypress and one lowly crabapple, among them.

The arborist can't plant just any tree. Chapter 39 of the City Code prohibits planting the American elm (too vulnerable to Dutch elm disease), silver maple (shallow roots that uproot sidewalks), weeping willows (you can't walk under them) and the female ginkgo tree (its fruit has a foul smell only a male ginkgo could love).

Gypsy moths are a preoccupation these days. Having had their fill of hardwood trees from Maine to Maryland, the moths are not expected to descend upon Northern Virginia until next summer. However, as any bureaucrat is bound to learn, "When trouble appears, the first thing one does is put in a supplemental request for more money," Hollings says. She has asked for $23,000 for pesticides to battle the tree-munching moths.

Hollings came to Alexandria in 1954, from the English town of Newbury, south of Oxford. While rearing her four children she dug right in, so to speak, into the city's volunteer beautification committee, learning landscaping at George Washington University.

In tree-conscious Alexandria, where all the historic trees sport plaques attached by special nails, being British hasn't hurt. "We've got this reputation of being wonderful gardeners," she says.

As arborist, she spends much of her time diplomatically arbitrating citizen complaints and tree-related squabbles.

She gets all kinds, as many as 100 a month. She's recruited at least 50 of the complainants into her tree aides corps. "They take care of the trees and tell me if they're looking sad," says Hollings.

Some of the complaints have nothing to do with city trees, and others have less to do with antisocial trees than humans, like the man who called Hollings to complain that someone was relieving himself on the city oak outside his door.

There are constant arguments between neighbors over their trees, says Hollings. "The first thing I tell people to do is talk to each other. Most often, by that time, they aren't speaking. It's surprising how often people aren't talking to their neighbors."