One by one, massive sculptures of granite, copper, stainless steel and marble have appeared on a grassy knoll at the University of Minnesota Landscape Arboretum in Chanhassen — markers of the most dramatic way the metro area landmark is expanding its attractions beyond greenery.

Thanks to an unprecedented donation by a retired Wayzata couple, the arboretum has acquired in one fell swoop a permanent new sculpture garden with 23 world-class art works that normally would take many years and millions of dollars to collect.

The full collection, to be dedicated Aug. 24, is one of several planned projects intended to draw more visitors by adding attractions to the arboretum’s 1,137 acres of plants, trees and flower collections.

Operations director Pete Moe said the arboretum, located 22 miles southwest of Minneapolis, is in various stages of planning or raising money for a Chinese garden, a treetop canopy walk, a bee education center at its historic red barn, and a woodland performance space to be developed in the next few years.

The intent is to appeal to a wide range of people who love gardening, landscape architecture, bird-watching and wildlife, native plants and art, Moe said. “We think that they’re all complementary,” he said.

Asked if some might prefer trees and plants to a hill full of art works, arboretum spokeswoman Judy Hohmann said the arboretum has 36 sculptures along its gardens and trails, and the new sculpture garden only occupies three acres.

“An arboretum is not a nature preserve,” she said. “We have display gardens and ­collections, but we’re always trying to engage visitors with the landscape and with nature, and this is yet another opportunity to do that.”

The highly visible location — three acres at the highest point in the arboretum — was one of the reasons Alfred and Ingrid Harrison donated the contemporary sculptures they’ve enjoyed for years on their property. “We’re both in our 70s, so it’s a time of life where you think what’s going to happen to them when you pass on,” he said in an interview.

The gift is a “thank you” to the public for the life and friends the couple has enjoyed for so many years, he said, and the location is perfect. “We wanted them really to be out in the open so people could have a visual experience that is in harmony with nature,” he said.

Art from around the world

The Harrisons were closely involved with decisions about where each sculpture would be located on the hill in relation to one another, said Susan Hamerski, the arboretum’s manager of adult education and curator of sculpture. The collection includes 23 sculptures spread out on the hill, with three more to follow in the future.

During a recent stroll, Hamerski stepped along a newly laid asphalt path that winds to the top of the hill. The sculptures are mounted on bases with plaques, so all that remains before the dedication is adding landscaping and borders.

The artists come from several countries, including Italy, France, England, Zimbabwe and Argentina, and include Mimmo Paladino, Paul Granlund, Rene Kung, George Rickey and Barbara Hepworth.

The oldest of the sculptures dates to 1960, but seven of them were created since 2000.

Art that embraces nature

One of the most striking works is at the base of the hill, a life-size bronze sculpture of an Apache mountain spirit dancer. The work by Craig Dan Goseyun features a dynamic crouching figure with detailed boots and flying fringes on his leggings, but with an abstract face and pointed headgear turned toward the sky.

Nearby, a granite disc with a square hole in its center looks like a giant mounted Chinese coin. The work by U.S.-based artist Jesus Bautista Moroles frames the surrounding Kentucky coffee trees and hillside as viewers walk around it.

Hamerski said that many of the sculptures interact with nature, including some that move in the wind and others that will include water features. “They definitely have a real relationship with nature and with the outdoors and with the plants that are around them in the landscape,” she said. That will also be true as sunlight and shade changes daily, she said, and as the seasons change around the sculptures.

The sculptures came with an endowment for perpetual care, so none of the expenses will come from membership or gate fees, Hamerski said. The total gift, including installation, is valued at $7 million, she said.

Interest already intense

Visitors can see most of the sculptures by tram or car from Three-Mile Drive, which meanders through the arboretum, or they can park near the hill and walk among the sculptures for closer inspection.

Although the official opening is a month away, drivers last week were already jumping out of cars to snap photos. Walkers such as Rebecca Dodson of Orono viewed the sculptures at closer range but from behind temporary rope lines.

Dodson is amazed that one couple was able to collect such diverse sculptures, and can’t wait for the final landscaping. “We’ve been waiting for this,” she said. “They’ve been installing them all winter.”

Harrison said he and his wife have “an enormous sense of satisfaction” about their donation. “As with any art, paintings or anything else, you’re only a temporary owner of any piece,” he said. “What’s left is for people to enjoy through the ages.”