W. MARK AND J. REIMER COURTESY OF SELECTREE WEBSITE

The pyramidal European hornbeam (Carpinus betulus 'Fastigiata') has shape well-suited for tree lawns.

IN A COLUMN a year ago, I praised the shade, leafiness and sense of scale that street trees bring to a neighborhood, and decried all the bare parking strips around town. Since then I've heard from a number of frustrated gardeners who love trees, too, but have just about given up on street trees because of heaving sidewalks, broken sewer lines or problems with overhead wires.

Nearly all the trouble-making trees are on the city of Seattle's recommended list for street trees.

The beautiful flame ash trees (Fraxinus augustifolia `Raywood'), which are the sole reason I drive to work along 35th Avenue Northeast, are wreaking havoc with miles of sidewalk. Purple-leafed ornamental plums (Prunus cerasifera) planted along many city streets are so riddled with disease as to appear deformed. If you want trees with city manners, where to turn?

One of the problems with getting good and reliable information is that plants have most often been studied in terms of production - how to make an acre produce the most apples or cabbages. The Center for Urban Horticulture at the University of Washington was established in the early 1980s to study plants in a different way, to explore the science and art of growing plants in urban environments. The center's brochure lists as one focus the study of how plant roots function under pavement. Sounds like street trees to me.

Linda Chalker-Scott, associate professor of landscape plant management at the center, finds herself pointing out to students the problems with many of the street trees in Seattle.

She thinks trees on the city's recommended list are too often chosen from the above-ground point of view, because of traditional use or aesthetics. Most disasters, however, are hidden underground until brought all too noticeably to the surface. She points out that the sweetgums (Liquidambar) breaking up sidewalks all over the University District are still on the city's list of recommended street trees. A student recently took her aback by asking which, if any, of the many trees listed, really are good to use as street trees. Chalker-Scott was faced with the question homeowners are asking: Are there any trouble-free street trees?

Now In Bloom The corkscrew hazel (Corylus avellana 'Contorta') is a large shrub with twisted and gnarled branches that show best in winter when the coarse leaves don't hide its fantastical shape. By late February, its yellow catkins lengthen to several inches, dripping down among the gnarled shoots for some late-winter garden drama.

"We used to think of roots as shaped like a big carrot," Chalker-Scott explains, "but now we know that most roots spread widely in the top 18 to 24 inches of soil."

In other words, more potato pancake than carrot. So before you choose any tree, remember that the root spread will equal 2 1/2 times the diameter of the tree's crown at maturity - a dimension with implications for trees in your garden, too.

In addition to the obvious size, shape and hardiness issues, Chalker-Scott lists these criteria to consider when choosing a street tree: potential for root troubles; disease and insect problems; visibility for traffic and views (few tree lawns are wide enough for multi-trunked trees); potential invasiveness; and life span (many trees die sooner in the city than in their native environments).

All these criteria and more are part of an interactive Web site called SelecTree created by the California Department of Forestry. The site has more than 4,000 photos of trees, and all the information needed to match species to sites. Enter the name of a tree and you'll get several pages of information on that tree, or you can search by site characteristics (shady, dry, hot) or tree characteristics, such as height, hardiness, flower color and bloom time. The site is easy to use and fascinating.

The more you know about any subject the harder it is to be unequivocal, but Chalker-Scott has a few trees she is willing to recommend as street trees. Her personal favorite is the Chancellor linden (Tilia cordata `Chancole'). The golden-rain tree (Koelreuteria paniculata) is both drought- and smog-tolerant. The pyramidal European hornbeam (Carpinus betulus `Fastigiata') is well-shaped. Parrotia persica has fine fall color, as do the maples Acer campestre and Amur maple (A. ginnala).

What would Chalker-Scott put in the parking strip of her own house? "I'd use all native plants, as they have the best chance with drought and disease."

Valerie Easton is a horticultural librarian and writes about plants and gardens for Pacific Northwest magazine. She is the co-author of "Artists in Their Gardens" from Sasquatch Books. Her e-mail address is vjeaston@aol.com