When I showed up at David Culp’s lecture on Layered Gardens at New England Grows in Boston earlier this month, I figured he would discuss the depth of his garden beds – with the taller plants at the back, and progressively shorter plants toward the front.

Culp did discuss that principle of design. He even expands on it by sloping his beds so that the backs are foot or two higher than the fronts, and the plants at the back are therefore more visible.

However, there are other layers in a garden, including the layer of time, with a plant and a garden changing as the year progresses, and as the years succeed each other.

“The garden has a changing look over all four seasons,” he said. “I love the spring garden, especially after a hard winter. But I also love the look of the fallen rose at the end of the season. It is all good, just different.”

Culp is director of sales and marketing for Sunny Border Nurseries, based in Connecticut, but gardens at his two-acre home in Downingtown, Pa.

The gardens at Brandywine Cottage, the name Culp gave his home, are designed to look natural, but he did start out with a plan – a plan that he believes goes with a house built in the 1790s.

“The gardens are geometric, which is more formal,” he said. “Being a plant collector, I think the lines bring order to the garden. Circuitous borders are more Victorian.”

He put his vegetable garden in the center of the garden and because he wanted it to be visible and not up against the boundary line with his neighbors, which he screened by giving the neighbor some pine trees.

He follows the practice of many gardeners by having the gardens near the house formal, but letting the design get looser farther away. At one side of the garden is a hillside, which contains a lot of full-size trees and where he puts in understory plants – and that creates layers of height. If a tree dies in that area, he leaves it up unless it uproots itself, in part because it looks natural and in part because it provides habitat for wildlife.

Culp does something I have never considered in a plant design. He groups plants that bloom at the same time. So in spring, there is a profusion of blooms close to the house. In mid-season, the preponderance of blooms are in a different area.

“I have different peaks of bloom time, but the transitions are soft,” he said. “The layered garden is about the relationships of the borders and space. It often has three plants interacting with each other.”

Culp has a lot of tall plants in his garden, partly because he wants to create that feeling of awe he had as a child in his grandmother’s garden of being surrounded by plants that were so much larger than he is.

Plant shapes are important in his garden.

“When it comes to color, it is not color first. It is texture first,” he said. “Color is mood, texture is emotion.”

You check out texture by doing a black-and-white photo, and if you can’t find the focal point in that photo, it is time to put in a statue, he said.

In one section of the garden he has a lot of verticals, beginning with trees. Then he adds a lot of vertical plants, including salvia, German iris, foxgloves and others, with a tall trellis and a bit of picket fence.

He puts the small, beautiful plants close to his house, including the hellebores, which he loves. He has created an entire line of hellebore hybrids called the Brandywine series.

The path to his house is lined with primrose, which looks good, but also because “I love to say I have led people down the primrose path.”

Most of his garden is perennials and shrubs, but he has a lot of huge tropical foliage plants that he mixes in just because they look good. He changes the containers at the entrance to his house seven times a year so they always look perfect. They are small and easy to move, he said.

He spent a lot of time figuring out how to create a seating area and driveway in a 1790s house because brick and paved stone would not be right for the time, so he went with gravel – letting a lot of tough plants grow right in the gravel. Which worked quite well until a visitor arrived at his house before Culp did, and the visitor spent his time weeding the driveway.

He has no problems with making mistakes.

“Making a mess is part of creative process, part of working it out,” Culp said. “Think of all the chefs who started out with mud pies.”

Another good quote: “In love or cooking you should be reckless. With time and ingenuity, everything can be answered with ‘yes.’ ”

He said he likes to weed his garden, because that is the time he gets down and looks at the plants really closely and sees how the leaves unfurl and the blossoms start to come out.

And he loves watching the garden evolve.

“A garden is never done and I don’t want it to be done,” he said. “A garden is a process, not a product.”

Tom Atwell has been writing the Maine Gardener column since 2004. He can be contacted at 767-2297 or at:

tomatwell@me.com