A few years ago, I went for a drive through the winding streets of Emery Manor, a subdivision of small, Levittown-like rambler houses built in the Chicago suburbs in the early 1950s. People in the older neighborhoods nearby said terrible things about Emery Manor when it was going up: They called it a drab, tasteless collection of identical tiny boxes, scarcely better than shacks. Wait 20 years, people insisted, and Emery Manor would be a slum.

Well, I didn't get there for 40 years, but when I did arrive, I saw something that surprised me. Not only wasn't Emery Manor a slum--it was very pretty. Each block had a placid, dignified, welcoming look that suggested a comfortable place to live. The houses were still small, but there was nothing tacky about the neighborhood.

Why was that? I can give you the answer in one short word: trees. Whoever did the planting in Emery Manor was either smart or lucky. The skinny saplings put in at the beginning had grown up to become a green canopy of big, healthy oak and maple trees, giving the whole place a leafy appearance equal to anything you would find in the more affluent subdivisions down the road. It's amazing how much better a cracker- box house can look with a 75-foot oak tree in the front yard.

But here's what puzzled me. America is full of subdivisions built in the 1950s and '60s. By now, most of them should be looking as good as Emery Manor. As you may have noticed, most of them don't. I've been through quite a few that seem almost as sterile as the day construction began. I think that's because the trees aren't there.

Such impressions can be misleading, of course, but numbers back them up. The American Forestry Association has been running sophisticated computer studies of the tree cover in large metropolitan areas, and what it's finding is that the nation's residential districts are a lot less leafy than they aesthetically should be.

The AFA recommends that an urban neighborhood should have a tree cover of roughly 25 percent, and a suburb, with more space for planting, should be closer to 50 percent. Metro-wide, a reasonable goal is 40 percent. But very few places are close to that target, even in the moist and tree-friendly East and Midwest. Atlanta lost 60 percent of its tree cover during the past two decades, and one-third in just seven years during the 1990s. The Baltimore area, with the age and climate to be a tree-lover's paradise, was down to barely 30 percent.

It's easy to jump to the conclusion that the chief culprit in all this is sprawl: Money-hungry developers chopped down trees and replaced them with asphalt and concrete. But arborists will tell you that sprawl itself is only a minor contributor to the problem. The real cause of "Disappearing Tree Syndrome" has more to do with bad cultivation decisions made three and four decades ago.

Leonard Phillips, editor of City Trees magazine and perhaps the nation's most respected urban arborist, says that plenty of planting was done in the postwar years, but mostly it was the wrong trees in the wrong locations.

Eager to attract nervous homebuyers worried about moving into an arid wasteland, developers and landscapers looked for cheap trees that would shoot up from the ground as quickly as possible. They went for Silver Maples, which grew extraordinarily fast but had trouble surviving storms, and crabapples, which were highly sensitive to disease. And they tended to place the trees out in the median, next to the street, where they got hit with automobile exhaust and where their roots had little room to spread out.

So a large proportion of what was planted in the early postwar years didn't last very long. But that's only part of the problem. Local ordinances tend to be very specific in requiring a developer to plant trees when a project goes up, but say very little about what must be done to maintain the canopy as the years go by. In many cases, the maples and crabapples that died in the '70s and '80s simply weren't replaced. They weren't anyone's immediate responsibility.

Even under the best of conditions, a tree doesn't last forever. Neighborhood chauvinists love to tell stories about ancient oaks that date back to the 19th century, but the truth is there are really very few of these. The AFA places the average lifetime of a tree on an ordinary American residential street at 37 years. That means that a large proportion of the oaks and maples planted in postwar suburbia would be getting old now, even if they had been handled properly in the beginning, which most of them weren't. The AFA estimated in the early 1990s that tree-planting nationwide stood at only about 27 percent of replacement level, and that 56 percent of the available planting spaces in residential areas were actually vacant.

That's not to say that there haven't been some genuine success stories. When Leonard Phillips was tree superintendent in Wellesley, Massachusetts, in the 1970s and '80s, and landscape architect, from 1993 to 1999, he came up with a classically simple and workable idea. Rather than planting new trees out in the median, Phillips started planting them on the front lawns of private homes, back about 20 feet or so from the street, much better protected from wear and tear. His guess is that a tree that lives 40 years out by the street might last 75 in somebody's yard, safe from pollution but equally enhancing to the local landscape.

The city tree wardens (an elected body in Wellesley) picked out the locations they wanted, but the homeowners got to choose the type of tree from an approved list (or choose none at all, if they preferred). The city paid for the planting; after that, it was the homeowner's responsibility to maintain it. Two decades after the program was launched, the number of public street trees in Wellesley had declined from 12,000 to 3,000, but the number on private property had gone from 32,000 to 54,000. The departmental operating costs had declined from $100,000 a year to $25,000, chiefly because the maintenance staff had been reduced from six employees to one: The residents were doing nearly all the work.

That's not a solution that can succeed everywhere. There are quite a few places around the country where ordinances prohibit the planting of trees by local government on private property. And Wellesley, in addition to being a highly affluent suburb of Boston, is--shall we say--a little tree-obsessed. It boasts of having 90 "state champion" trees--biggest of their particular kind anywhere in Massachusetts. Wellesley offers visitors a 25-mile "tree watch" driving tour, in which it shows off 100 of its prize specimens. All of this will strike some cities as more than they want to do in the name of arboriculture.

Still, any community that wants an effective and far-sighted program can probably have one. Unfortunately, not too many of them are trying. The last decade wasn't especially kind to municipal cultivation budgets. Towns all over the country slashed their spending for tree maintenance during the recession of the early '90s; then, when fiscal conditions improved a few years later, found better things to do with their money than restore the jobs on the arborist's staff. Even Wellesley wasn't immune to the trend. To save money, it moved its landscape architect into the Highway Department, then eliminated the position altogether. Leonard Phillips ended up in the private consulting business.

Municipal stinginess is the bad news on the urban forestry front during the past few years. The good news is an enormous burst of volunteer activism that has gone a long way toward making up for it.

What's happened is not exactly a coincidence. In 1990, without most people even noticing, President George Bush signed the America the Beautiful Act, which among its provisions endowed the "National Tree Trust," charged with the task of stimulating volunteer arborists at the local level throughout the country. The same year, Congress established a National Urban and Community Forestry Advisory Council to do essentially the same thing.

What's happened since then provides a good lesson to those who don't think all those obscure and overlapping federal programs with weird acronyms ever accomplish anything. The federal laws have helped generate a huge outburst of urban forestry activism, from Baton Rouge Green in Louisiana to Plant Amnesty in Seattle and to the Tree Pruners of Ithaca, New York, whose members roam around the city snipping off limbs that are due for snipping. An Alliance for Community Trees serves as clearinghouse and support network for the whole process.

To a great extent, these groups have taken over jobs that local governments used to do--perhaps even some that they still should be doing. The professionals have decidedly mixed feelings about what has gone on.

"We in the trade call them the tree-huggers," Leonard Phillips says. "They've got the political ability to go in and ask for things that the city arborist can't get. On the other hand, they don't have the professional expertise to take care of the trees once they are planted."

This is a dispute I have no intention of getting into. What seems important to me is that, a generation ago, we had a chance to turn thousands of our neighborhoods into green, sheltering places, and we blew it. If enough people take an interest, we may get another chance.

At the very least, I have learned to appreciate the 65-year-old magnolia tree in my back yard that sheds leaves all year, pushes its roots in every direction, and makes it almost impossible to mow the grass. In many ways, it's a nuisance. But if anybody ever comes to cut it down, I'll be there to hug it until they go away.