On a steamy August day, Diane Erdmann's back yard might just be the coolest spot in town, literally and figuratively. The gurgling waterfalls and canopy of ancient oaks seem to stave off the actual heat (and, somehow, the humidity), and the sprawling, seemingly laissez-faire layout — an alluring Arctic willow here, outsized ostrich ferns there — is sensuously soothing.

Erdmann calls her sloping south Minneapolis back yard "a mix of architecture and 'let it happen,' " with volunteer plants strewn throughout. Ligularia poke out of pondside rocks, ground cover becomes stone covers on paths and steps, and a pagoda dogwood has stayed put years after meeting its maker.

"We left it because the birds like to perch there," she said. "So often we take out the dead wood, and that's where the life is."

As if on cue, a goldfinch alights on the dogwood.

That flash of wings provides a rare bit of color in the deeply shaded lot, where 17 kinds of trees put the focus on plants such as spiderwort, tamarack procured from some ditch-diggers Up North, rhododendron, wild geranium.

Summer brings splashes of color, not counting the endless shades of green. But the showiest season arrives in just a few weeks — assuming this infernal winter ever ends — when the hillside will be a resplendent blanket of Siberian squill. "When nothing else is blooming," she said, "it looks like a carpet of blue paint back here."

The yard was barren, a "blank slate," when Diane and John Erdmann bought the house 15 years ago from his mother. John had grown up there, playing in a treehouse built into a bur oak "that was big when he was little," she said.

Their challenge: creating a landscape that didn't look landscape-y.

"I have always loved being in the natural world and gardens," said Erdmann, a teacher at Richfield S.T.E.M. School. "This is a way of engineering those environments in the city."

The back yard, she determined, should be a sanctuary for wildlife, including the two-legged variety.

Over the years she put in native plants such as Solomon's seal and river birch; welcomed "volunteers"; had the three-terraced pond and a waterfall installed by a friend, and "ripped out the creeping Charlie; that was a lot of large bags" and replaced it, mostly with Virginia creeper.

The ground cover provides more than a lived-in look. "It keeps the moisture in," Erdmann said as she pointed to some sphagnum moss. "I don't water back here much at all. It's like a microclimate — it has a little rain-forest thing going on."

A gift set

While the back yard is a "gift to the natural world, from which we borrow our space," Erdmann said, other spaces pay homage to hominids: The bloom-happy front yard is dedicated to her mother and the nourishment-geared side yard to the farmers on her father's side of the family.

They, too, are integrated seamlessly with a home that was built in 1905 as a lakehouse. (It's within a few blocks of both Calhoun and Harriet.)

The curved pathway leading to the front porch is lined with coneflower clumps, currant tomatoes, a Korean lilac bush, a volunteer rudbeckia and other native plants.

Containers bear non-natives such as pomegranates and succulents. ("If we have that climate change thing, the yucca's going to do really well here," Erdmann said with a grin.) Wild strawberries, which she encourages the neighbor kids to munch on, provide ground cover.

Trellised up the south side of the porch are grapevines. Just past a "butterfly crossing" sign amid a spread of milkweed, the fruit orchard and vegetable garden unfold. Blueberries, kale, herbs, melons and tomatoes share the sun-splashed space with sunflowers entwined with Cherokee bean vines and a year-old peach tree. More mature stone fruit comes from a pair of apricot trees, prolific enough to ensure that "everybody gets apricot jam for Christmas."

Erdmann brings her nature-loving side to her cooking. When the kale comes in, she sautés it with … a weed called wood sorrel. "It gives the dish a lemony flavor," she said. "It's a Euell Gibbons kind of thing."

Citing Gibbons, the late wild-edibles advocate, is natural for such a plant and animal lover, a woman who has designed a yard so that it doesn't seem designed. The better to savor it rather than constantly toiling in it.

"It's kind of a lazy garden," Erdmann said. "I like to put stuff in that can take care of itself. … Plants that die are replaced by something new, or are adapted to a new purpose.

"I think it is really about allowing changes, whether purposeful or accidental, to lead into new forms."

Bill Ward • 612-673-7643