A black lawn by Andrew Dadson, and nearby (not pictured), an awning for nothing by Jenny Heishman. Kelly O

The Olympic Sculpture Park's official opening was in 2007, but its real opening was last weekend. Before that, it was a museum—predictable and self-protected, with don't-touch signs and art made of concrete and steel. Now the oxygen mask has been lifted, and the park has drawn its first breath of city air. Five new temporary installations are scattered around the grounds: a washer, dryer, and TV console, all made of plywood, discarded in the tall weeds on a hill (by Whiting Tennis); a meadow of long grasses spray-painted black in the shape of a giant square (Andrew Dadson); a homemade hammock hanging in the trees with a large ceramic lump sitting on it (Jessica Jackson Hutchins); a green-and-white-striped awning high on a gray concrete wall near a turtle-shaped topiary (Jenny Heishman); and a soundtrack of whale songs sped up so they sound like birds, and bird calls slowed down so they sound like whales (Mungo Thomson). These are all by West Coast artists—two from Seattle, one from Portland, one from Vancouver, BC, and one from L.A.—and they will be removed after September 12.

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The park has seen guerrilla interventions and one-night installations before, but this summer marks the first organized exhibition of ephemeral sculpture at the park. It's not too soon to say that this should happen every year. With a little spray paint, some twisted fabric, and a few hunks of clay—just a few maneuvers by a few great contemporary artists on a fixed budget—the environment is transformed, and some of the permanent pieces are upstaged by the upstarts.

"I think that's supposed to be a big fish," a man explained last Saturday while looking up at Mark di Suvero's big painted steel abstraction of a fish from 1992, called (pretentiously) Schubert Sonata. It's both overblown and underwhelming. Across the path from it are Jenny Heishman's three sculptures, curious but clear to anyone. The cheerfully colored awning suspended in mid-concrete adorns nothing—it's out of work, unemployed, sheltering no doorway and announcing no event. The topiary nearby is far enough away to seem disconnected from the awning; it appears like a transplant from a conspicuously fake place, contrasting with the preciously native plantings of the park (at the Olympic Sculpture Park, even the plants have plaques). A beach-blanket inset in the hillside, also by Heishman, is made of tiles of marble, the hard stuff of gravestones and classical sculpture. Together, the awning, topiary (Heishman grew it in her own yard for three years), and marble blanket bring something Floridian, a bit of the Sunshine State that's also so famous for its natural (and aesthetic) disasters.

The temporary installations are meant to sustain repeated visits. You'll probably miss some of them your first time (I did, even accounting for the fact that Mungo Thomson's sound piece was on the fritz for technical reasons). Some of the pieces are hiding in groves of trees or along paths not taken this time, while others are out in plain sight but camouflaged (a topiary being easily mistaken for a topiary). This is not a drawback; it is a pleasure. Wandering around in a landscape with no map, no checklist, is an adventure beyond tourism.

This is a park, and this is summer, and so everything has a certain lightness of being. The tops of Whiting Tennis's strewn-about, life-size TV and washer/dryer poke up from the weeds like cat's ears. And yet when you come close to this old furniture thrown out and left for dead, the place feels more like an alley than a meadow, the cat feral and suffering. On Saturday, a man rested his hand on the dryer's painted surface as he waited for his ladyfriend, a gesture both sympathetic and casual. Nobody told him he could touch this art, he just knew.

Tennis's discarded home furnishings also symbolize litter. They date from sometime in the 1970s—pull open the cabinet on top of the TV, and you'll find a plywood record player with a nail for a needle, queued up to play a 7-inch of Creedence Clearwater Revival's "Up Around the Bend"—and they represent the remnants of a household dissolved. Maybe in a hurry? Maybe there was a death? It feels like a portrait of an older, single man (maybe even a self-portrait). The artist says whatever decay and dirt happen this summer are part of the piece.

When Andrew Dadson spray-paints a huge square section of a meadow black, it looks like he burned it. Like Tennis's field of litter, Dadson's square of grass appears to be a misanthropic act that takes a beautiful form, evoking spectacles of environmental abuse and disaster. Up close, the pink and purple wildflowers and yellow ladybugs appear to be survivors of the blast; from a distance, the long grass has been swept in swaths by the pressure of the paint and looks like an unruly fur rug (modernist black square becomes postmodern pelt). The black painting looks west across Elliott Avenue, facing Tony Smith's black sculptures designed in the 1960s, Stinger and Wandering Rocks, as both a continuation and a response. (Tennis's haphazard arrangement is reminiscent of Wandering Rocks, a series of black gemlike objects that can be displayed any side up, as if they've been scattered like dice.)

The temporary installations reflect what's already there. While Heishman's topiary sticks up from a manicured lawn, Dadson and Tennis draw your attention to the weedy other half of the park, heightening your awareness that this tame/wild system governs the park and influences the way all the sculptures are experienced.

There are almost no bodies at Olympic Sculpture Park, save the ones of the visitors. The taut steel bodies of Louise Bourgeois's father-and-son fountain sculpture—the park's only overt figures—are inhuman. Jessica Jackson Hutchins's ceramic blobs and bulges cradled in hammocks are abstract, strictly speaking. They are not skin, but their surfaces are mottled browns, pinks, and blues. They don't have bones, but they sit up straight and poke down through the hammocks' blankety webs of found macramé and old clothes. Bourgeois's fountain has always seemed bland and anti-Bourgeois; one imagines the great spirit of the recently dead artist in Hutchins's joyful, plump, sexy forms.

The installations are owned by the artists, and the land is owned by the museum, but given the free admission of the park, this display ups the game of public art in Seattle with one fell swoop. It demonstrates that impermanence is a public good that can't be simulated. recommended