These Amelanchiar x grandiflora, which top out at 20 feet, were planted five years ago along a paved pedestrian trail in Lake Forest Park. In spring they are a haze of white flowers underplanted with narcissus, in summer a froth of Stipa tenuissima skirts their trunks, and in autumn their leaves turn shades of vivid red.

Seattle City Arborist Nolan Rundquist responded calmly and thoughtfully (bless the man!), explaining that Seattle's street-tree activists are determined to see their neighborhoods planted up. "There are so many folks who just love trees," says Rundquist. One of the things he's learned in more than 20 years as a municipal arborist is that any type of tree, regardless of species or size, has the ability to cause damage if incorrectly sited. He hesitates to condemn any species, and is also reluctant to declare any foolproof.

Not surprisingly, then, the city's street-tree list is under constant revision. "The jury is still out on Bradford pears," says Rundquist. He has seen few problems with paperbark maple (Acer griseum), Rocky Mountain glow maple (A. grandidentatum 'Schmidt') or serviceberries. Amelanchiar x grandiflora and its cultivar, 'Princess Diana,' are on the city's recommended small-tree planting list.

Rundquist tells of a rhododendron that heaved a sidewalk when planted in severely compacted soil, and of a statuesque sweetgum causing no problems despite being squeezed into a 48-inch-wide strip. It all comes down to right plant, right place. The problems come when trees are planted along the street without a permit, selected without the advice of the City Arborist's office or placed under wires or in too narrow a space.

"I'm the Frank Sinatra of parking strips — they have to do it my way," laughs Rundquist, explaining that parking strips don't really belong to the homeowner — they are dedicated to the public use in perpetuity. It is, however, the homeowner's responsibility to water, prune and care for whatever is planted out there. Trees cannot be topped, and a permit is required to prune any branches larger than 3 inches in diameter. The city provides pruning guidelines and enforces pruning regulations to try to keep trees healthy, safe and looking their best.

Now In Bloom Not all asters have daisy-like flowers. Aster lateriflorus 'Prince' has numerous tiny white button flowers centered with raspberry-colored disks, set off by purplish-black leaves. 'Prince' grows into a 30-inch bristly mound and blooms well into October.

Where to start if you'd like to plant your parking strip? You might contemplate the fact that any tree you plant will probably live (and grow) for 50 to 60 years, changing the face of your neighborhood. Don't even think about a tree unless your parking strip is a minimum of 5 feet wide. If you want to plant anything out there taller than perennials or groundcovers, you need a permit, which is free of charge. Once you send in your permit request, an arborist will come out to take a look, discuss possibilities and give advice on wires and locating utilities.

Once a tree is planted, it can pull all the water out of its planting hole in only five hours, and it is the homeowner's job to keep that tree healthy. Rundquist suggests drilling a 1/8-inch-wide weep hole in a 5-gallon plastic bucket, setting it next to the new tree, and filling the bucket with water every three to four days. For the first year, until the roots grow outside of the original planting hole, the tree needs plenty of water, and in subsequent years a more moderate amount. Remember that it is hot, windy, dry and exposed out there on the strip, with car exhaust and compacted soil, so each tree needs all the tender loving care you can give it, especially until it is well established.

Rules and regs may differ in unincorporated King County and each municipality, so be sure to check with your specific jurisdiction before you plant. No matter where you live, you can make use of the City Arborist office's common-sense standards and suggestions for siting and selecting street trees. Call the office at 206-684-7649 to receive a packet of information with descriptions of recommended trees and direct on how to apply for a permit. The same information is available at www.cityofseattle.net/td/arborist.asp.

Rundquist will be giving a two-hour street-tree primer class on Wednesday Oct. 17, 7 to 9 p.m. Call the Center for Urban Horticulture at 206-685-8033 for information on cost, location and how to register.

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. Mike Siegel is a Seattle Times staff photographer.