Standing amid huge bundles of willow branches, dogwood cuttings and box elder boughs, Patrick Dougherty tugged on a pair of well-worn gloves and set to work weaving branches into a two-story "castle" on a driveway island in front of the Minnesota Landscape Arboretum in Chaska. For the past three weeks the internationally known artist from North Carolina and about 80 volunteers were on a single-minded drive to make magic out of underbrush -- 6,000 pounds of spring prunings that would otherwise go to mulch. The results of their effort will debut Saturday morning in a ceremony that is a prelude to the arboretum's summer celebration of "Powerhouse Plants." Like all of Dougherty's work, the arboretum project is a fanciful mash-up of sculpture, architecture and botanical dreamscape. The structure is a temporary addition to the arboretum's landscape, expected to last about two years before it disintegrates under the pressure of weather and natural decay. Even so, it is sturdy enough for visitors to enter and explore, dodging in and out of doorways, wandering hallways under twig arches and peering up at the sky through four roofless towers hidden behind the castle-like outer walls.

Dougherty designed the structure on-site after a preliminary visit last summer to scope out possibilities. He rarely sketches his plans or builds models, but instead makes things up when he knows what materials are available.

"I'm always working through things I've thought about, but sometimes the site will change things on me," he said. "In this case I was concerned to have something that will stand against snow. I want people to be able to come onto the island and be able to go in further, to lose the sense of knowing where they are.

"But also it has lots of big openings and views, so you can't get trapped. I don't want any apprehension as you view and go through it."

During the past 25 years, Dougherty has erected more than 200 of his imaginative creations in parks, gardens and art museums from New York City to Honolulu. Abroad he's built them in Mexico, Japan and throughout Europe. His materials vary with geography and season, but there's something primordial about all of his stick structures.

In parks or gardens they look like primitive huts, witch's castles, enormous vases or nests for gigantic birds. Perched beside a reflecting pool, they may crouch like animals or twirl like dancers. For museums and galleries his designs are usually more abstract and conceptual -- wild mats of greenery that drop from ceilings, swirl down stairways and flow outside to encircle trees or embrace the pillars of a porch.

"Inevitably, there's a certain 'Blair Witch' thing going on," said Tom Rose, a University of Minnesota art professor and admirer of the sculptor's work. "Twigs and sticks tap into our unconscious fear of the forest, which is part of the fairy tale fantasy with the gingerbread house and Hansel and Gretel wandering off. You're entering into the wild, untamed aspect of nature. And there's a medieval quality to his odd, labyrinthine buildings. They're very dreamlike."

They're also very much like baskets, said volunteer Sherri West of Shorewood, who spent a recent morning threading leafy box elder trimmings into a tower wall. A basketmaker by profession, West said the random weave that Dougherty uses gives his constructions great structural integrity.

"A well-made basket can last for generations," said West. "This is his answer to the third little pig; it's very structural and can compete with the brick."

Building community

On-site, Dougherty works steadily and moves with a limber grace that belies his 64 years. Kneeling beside an opening in one of the towers, he showed a volunteer how to drive the stem of a willow bough into the ground and then thread its top into the emerging wall of twigs and branches. No nails, screws or other fasteners are used. All the branches are simply woven between trimmed saplings that were drilled 30 inches into the ground. To make the structures seem more animated and alive, he deliberately tilts them so they appear windblown. He's also very attentive to color and texture, using lime-green willow branches and red dogwood stems to accent wall openings, and darker twigs to create patterns of light and shadow.

"It's a little hobbit house in here," said volunteer Chip Abernethy, a retired flight attendant from Deephaven who worked with her brother Paul Peterson, a forester from Grand Rapids, Minn. He had taken a day off and driven four hours for the privilege of standing on a scaffolding in a cold wind, clipping branches. Longtime fans of Dougherty's work, Abernethy and Peterson allowed as how they might try to replicate a bit of the project later. "Maybe we'll try a small version for our mom's house in Grand Rapids," Abernethy said.

Each structure typically takes three weeks to build, which allows Dougherty to spend one week each month with his wife, Linda, chief curator at the North Carolina Museum of Art in Raleigh, and their 16-year-old son, Sam. He does 10 projects per year and is pretty much booked for the next three years.

The ephemeral nature of his work aligns Dougherty with other contemporary "nature" artists who do transitory art, including Andy Goldsworthy, who has sculpted with ice and leaves; Richard Long, who takes long walks and documents little changes in the landscape, or Christo and his late wife, Jeanne-Claude, who once surrounded some Florida islands with pink fabric.

Dougherty is more of an environmental educator, however, using his constructions to stimulate interest in the natural world.

"Patrick is not only a master weaver of plants, but also of people," said Sandy Tanck, the arboretum's manager of interpretation. "He takes the essence of a place and its plants and people and weaves them all together. How many other artists do you know who do their work by building community?"

mabbe@startribune.com • 612-673-4431