The 30-foot-high waterfall cascades down into a pool overlooked by vine maples, in a scene more mountainous than urban despite the fact it's right alongside the REI flagship store.

"We wanted people to get a slice of the mountains in the city," says Berger Partnership principal Greg Brower, who was project manager for the landscape at REI's flagship store. Planted eight years ago, spruce and fir branches form a shady canopy over the hiking and biking trails that surround the store, while snowberry, salal and Oregon grape cluster around their trunks.

It's true that this vast store offers what REI describes as "the motherlode of gear," but hiking boots and backpacks aren't the only things that make the place one of Seattle's top attractions. Visitors drape themselves on rocks to read or chat, lean over the balcony to get a good look at the massive waterfall, or spin along the bike trails testing out potential purchases. This is not only a landscape to immerse yourself in; it's also a functional one with space to teach classes, give demonstrations or track down a huckleberry bush.

LOOK FOR YOURSELF Recreational Equipment Co-Op and its landscaping is clearly visible from I-5, just off the Stewart Street exit at 222 Yale Ave. N.

While most of the plants are natives, the designers weren't purists. The upper entry is defined by a sweep of blue-blooming ceanothus, a plant native to California, and most of the rhododendrons hail from elsewhere. The point was flexibility, variety and a dose of seasonal color from vine maple, azaleas, dogwood and serviceberry in a predominantly evergreen landscape.

You'd never guess from all the luxuriant green that the original dirt around the building was heavy gray clay. The designers amended the muck with a foot of topsoil and a layer of rotting leaves and twigs. "It was that duff that kick-started that landscape," says Brower, whose team even brought in fallen cedar logs. "We did everything we could to replicate the natural system," he explains. A recent probe of the soil showed that the topsoil and duff had not only filtered down to improve the subsoil but also built up into an even thicker, richer top layer to nourish the plantings.

Now In Bloom Few garden trees take on coloration as vivid as sourwoods in autumn. Oxydendrum arboretum are slow-growing, reaching 15 to 25 feet high and beyond. Toward the end of summer, the branches drip with fragrant clusters of creamy flowers that turn to silvery-gray seed capsules persisting into winter. These seed cascades are shown to perfection later in autumn when the tree's leaves burn in colors of hot orange, scarlet and purple.

Heavy rainstorms are exciting at the store. Rainwater is collected off the roof and directed to the waterfall, so the water roars over the boulders with even more of a rush than usual. Imposing in scale, the waterfall is a series of boulders, ponds and falls stretching over 30 feet, helping mask the height and mass of the building as well as the sound of freeway traffic. The bridges and steps up to the store afford dramatic views of the tumbling water as well as the forest below.

The maintenance people have learned some things. Early on, they swept the leaves and picked up the twigs, but found out it all needed to remain beneath the trees as nature's own mulch. And, they found, there's no reason at all to prune, unless a branch gets in the way, because the lower levels of plantings were planned to flourish in the shade of the maturing trees and shrubs.

For most stores, the landscape consists of little more than a parking lot or garage and perhaps a few pots of seasonal flowers, a small investment compared with the building itself. But the forest surrounding REI stretches over 21,000 square feet, even though code required less than 3,000 square feet of landscaping. The waterfall alone cost more than $100,000. Brower explains the extra effort: "Even though it's a retail store, it's all about the outdoors."

Valerie Easton is a Seattle free-lance writer and contributing editor for Horticulture magazine. Her e-mail address is valeaston@comcast.net. Mike Siegel is a Seattle Times staff photographer.

More Plant Life columns