If ever there was a garden that has it all, it’s the River Hills garden of David and Dedi Knox.

Set on 15 acres, it has a formal boxwood-bordered rose garden, perennial and vegetable gardens, water and woodland gardens, pathways, a stream, four ponds, large expanses of lawn, a Gothic-inspired tree house, a pine forest, 100-year-old trees, new trees and garden art. 

There’s even an arboretum with collections of rare native, European and Asian trees and shrubs, and more than 60 magnolias.

Here unique trees were planted years ago, and hundreds more have been planted since the couple have owned it.

Dedi Knox is an artist who works with watercolors and oils, but David, who heads a foundation, spends his time “painting his landscapes,” where he has collected the many trees he loves.

“When I plant, I try to weave it all together like a painter would create a picture of a landscape. After we bought this land, I started painting with trees and other woody plants.

“This whole place is really an arboretum. I love the textures and colors of the leaves, and the way the trees flower in spring and later in fall. Especially the maples; they’re the most beautiful,” he said. “Trees are wonderful because they all have slightly different textures to their leaves. Some have leaves that are finely cut like the European fern leaf beech, some have reddish leaves like the European river beech, some turn green in summer, some have yellow leaves that stay yellow, and there are a lot of variegated trees and bushes.”

Knox said a considerable amount of work was done to the land after 1950 when Norman and Millie Chester bought 10 acres of it, built a home on it, then hired Chicago landscape architect Franz Lipp, who designed the gardens at Cantigny Park in Wheaton, Illinois, to create gardens near the house.

The Knoxes bought those 10 acres in 1984, and in 2004 they acquired five additional acres to the north.

But by the time they took charge of the properties, they had fallen into disrepair.

David Knox said his initial goal was to preserve and restore the surviving elements of Lipp’s design, and to clear the lands of invasive plants that covered it.

It proved to be a Herculean effort.

“The first few years we were getting rid of invasives on the 10 acres of land and in the ponds. Then, when we bought the five acres, it took a few years to do that, too, because it was also filled with invasives.

“The gardens were also constantly changing. At one point we lost 450 ash trees,” he said.

But he didn’t give up and today the land is filled with lush gardens and forests with plants in a variety of sizes, shapes, textures and colors.

There’s Margaret’s Garden, named after their oldest grandchild and located to west of the house, that includes a variety of trees, shrubs and perennials that Knox says illustrates the look he’s created throughout the property.

There’s also Anni’s Garden, a relaxing space named after another grandchild that surrounds the bottom portion of the upper pond. There he’s planted a Postelense, an English hedge maple; a Mariesii viburnum; an umbrella magnolia; and a variety of colorful perennials.

In the rose garden near the house there are about 100 hybrid tea roses including some Peace roses that date back to Lipp’s original design. The roses are surrounded by boxwood hedges and are underplanted with white Triumphator tulips.

The four stream-fed ponds at the edge of the woodlands are surrounded by wildflowers, trees and shrubs, and near one of the ponds there is a garden with a variety of dwarf conifers and Asian maples that are underplanted with lilium, daffodils, tulips, Siberian irises, snowflakes, naked ladies, and resurrection lilies.

There’s a mature pine forest made up of scotch pines with trunks that are partially free of branches, which creates a striking backdrop for a pond, and a hickory and linden forest that’s home to native ferns.

Here, in spring, Knox said the area is alive with drifts of native bloodroot, trout lilies, trillium, Virginia bluebells, spring beauty, daffodils, lilium, and fritillaria.

“There are wonderful wildflowers in the woods. One of the great things that’s happened over the years here is the carpet of wildflowers that’s grown. There are such beautiful wildflowers in spring.

“They were always there. You just have to take care of your property and give them a chance to grow and spread,” he said.

David Knox recently talked about his gardens, which will be opened to the public during The Garden Conservancy’s Milwaukee-Area Open Days program on June 24 and 25.

How important has creating this garden been to you?

It’s a passion. It’s more important than golf.

What’s the history of your home?

In 1950 Norman and Millie Chester bought the original 10 acres and built a 6,000-square-foot red brick Colonial Revival house here that was modeled after the Raleigh Tavern in Colonial Williamsburg. The work was done by architect Andrew H. Hepburn who did restoration work at Colonial Williamsburg. They named the property The Chimney because it has five large chimneys.

Why did you create an arboretum?

For landscape reasons. For color and texture. I am also seeing which species of trees can tolerate our climate as the average temperatures are changing. I’m trying to grow Zone 6 plants here.

What are some of your most unique trees?

The Hampton Court Gold horse chestnut … a rare variegated gingko, a Katsura, Chinese oak, American beech, European fern leaf beech, European weeping beech, golden chain tree, ironwood, stewartia, and the variegated tulip tree, which is in the magnolia family.

You have collections of trees. What are some favorites?

I have a collection of more than 40 maples. I also have a pretty good-sized collection of European beech trees, conifers, and a lot of Asian oaks. I have a whole plethora of things both native and non-native.

What are some of the biggest trees on your property?

There’s a white oak that’s approximately 100 years old, and a large European copper beech.

Are arboretums unique in private gardens?

I don’t think a lot of people collect trees — not to the extent that I do. 

How many trees have you planted over the years?

I can’t even imagine. I plant 20 to 30 new trees some years.

You do a lot of underplanting. What is the benefit?

It creates color and texture. For example in the rose garden I have the white Triumphator tulips between the roses, and in spring they come up between the roses that are dormant and you have these beautiful white blooms floating above the boxwood that surrounds the roses.

I also underplant with trees. They grow in the understory. In a large portion of the new five acres I have green ash I underplanted with sugar maples I transplanted from the woods where they were self-seeding. If the ashes came down I would have nothing there. I like to plant to have succession in case something happens to the big ones.

There are also a number of Asian maples that grow in the understory in a wooded area. That’s also where a lot of the magnolias are planted. If you have a big, tall canopy, light gets through there and you can grow all sorts of things. But they have to be things that will grow in partial shade.

How would you describe your style of gardening?

It’s a landscape garden with all sorts of elements in it. I can’t put a description on it. The rose garden is formal; the perennial garden is like an English cottage garden. It’s eclectic.

Who or what influenced you in gardening?

I went to Oxford (in England) for three years, and I fell in love with English gardens. That really shaped my interest in landscaped gardens.

But also by gardens in France, Italy and South Africa. The Morris Arboretum (in Philadelphia) and Mt. Cuba in Delaware have also been significant influences in planting schemes.

Individuals who have influenced me in my selection of plants for the arboretum include Paul Meyer, director of the Morris Arboretum in Philadelphia, and Alan Miller, who lives in Pleasant Valley, Pennsylvania. He’s a collector of Asian maples and conifers.

 Do you fertilize your plants to keep them looking so great?

Only if they would need it. No chemicals are used on the property.

How did you get rid of all of the invasives on your property without chemicals?

The garlic mustard is pulled by hand. The buckthorn I cut it down and then I kept brush cutting it every fall until it eventually relented. 

How much time do you spend in your gardens?

As much as possible. It’s my refuge, and it has been forever.

Did you have professional help designing your gardens?

The professional help I got was traveling and seeing gardens. I did all the designing myself. I was influenced by so many gardens.

Do you have help in the gardens these days?

When I started out I did everything myself. Now I have help.

With your wife being an artist, has she helped you with the design of the garden?

No. She’s not a gardener, but she appreciates it and paints it.

Can you tell me about your tree house?

I designed it. It was inspired by a six-sided faux stone garden building in Williamsburg. It has a decorative wood-shingled roof, a stained glass window, and there’s a chandelier inside. It’s in an old red oak. It’s a fantasy.

Where do you go to relax on your property?

I usually walk on the grass paths in the forest to the ponds. I like to walk rather than sit because I want to see what I need to do.

If you go

What: The Garden Conservancy’s 2023 Milwaukee-Area Open Days program. Tour six gardens on two weekends. In June there will be one in Port Washington and two in River Hills. In August there will be two in Whitefish Bay and one in Brown Deer.

June location change: Afterglow Farms will only be open June 25. The Vineyard at River Hills will be open in its place on June 24.

When: 10 a.m. to 4 p.m. June 24-25 and Aug. 19-20.  

Extras:  At 10 a.m. and 2 p.m. Aug. 19 there will be a special Digging Deeper event in River Hills, “Discover the Magic of Greenfire Woods,” where the owner will talk about a lifetime in her garden and give a tour of an old-growth forest, wild areas, and a cottage garden with artisanal features.

Tickets: $10 per person per garden for the Open Days tour. Children 12 and under are free with a paid adult admission. The Digging Deeper event is $40 per person. Discounts for Garden Conservancy members. Advance purchase required for all events, and tickets are limited.

For more information and tickets: See gardenconservancy.org/open-days/milwaukee or gardenclubgreatermilwaukee.org.