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3. Wildflower Gardens: Designing With Nature
by C. Colston Burrell
Patterns are common in nature. From the shadows cast by dancing leaves, to ripples in a pond, to overlapping mountain ridges that fade into the haze, natural patterns surround us. In addition to these obvious patterns, there are subtle ones created by the structure of plant communities and the positions plants take in the landscape. Once you understand the factors that create these natural patterns, you can use them to design your wildflower garden.
Vertical Patterns
Every native plant community, whether forest or grassland, wetland or desert, has a discernible structure based on the dominant and subordinant vegetation. The species in any plant community form vertical layers or strata. A forest has a towering canopy of trees that influences what can and cannot grow beneath it. In a maple-basswood forest, for example, the 30- to 100-foot canopy is high and dense, producing a cathedral-like effect. The canopy is interwoven and connected to form a ceiling over the entire forest. The foliage captures much of the light, protects the forest interior from rapid temperature fluctuations, and cools the air through evapotranspiration.
Smaller trees such as dogwoods and shadblows make up the airy understory. Understory trees from 30 to 12 feet tall form a more intimate ceiling. Beneath these trees is the shrub layer, between 12 and three feet above the ground, in scattered patches where light and space are sufficient. The shrub layer is a critical foraging and nesting area for a variety of forest birds. Below the shrubs is the ground layer of wildflowers, grasses, sedges, and ferns. Here, spring ephemerals such as spring-beauty bloom first, followed by taller ferns and persistent species like merrybells.
The age of a plant community affects its distribution, composition, and structure. A young forest often has a well-defined shrub layer and understory. Older forests with dense, closed canopies may have fewer ephemeral plants and more persistent or evergreen wildflowers and ferns. The structure of a forest also varies according to the tree species present. Deciduous forests have the most traditional structure, as described above. By comparison, in a dense woodland of coniferous trees, the understory is very thin, but there is often a thick shrub layer, with herbs and mosses carpeting the ground. Coniferous forests have more open canopies, with scattered understory trees and the well-defined shrub layer. Shrub communities have mixed layers of different-sized shrubs, with a ground layer of herbs, grasses, and sedges.
In meadows, prairies, and other communities dominated by herbaceous plants, the vertical structure is no less distinct. However, unlike the trees and shrubs in forests, the plants must resprout from their roots each year. The earliest plants to emerge in the spring, such as violets, are short. Each successive wave of plants to emerge overtops the next, culminating with the tallest grasses and late-blooming composites, such as sunflowers and asters.
Horizontal Patterns
Kansas gayfeather (Liatris pycnostachya) makes a striking statement blooming in midsummer. Photo © C. Colston Burrell
Plants within a given community are also distributed in horizontal patterns on the landscape as a result of environmental factors such as soil, moisture, and light. Different species thrive with various amounts of moisture. In a prairie, shrubs grow in the wettest areas, whereas grasses and herbs grow in the slightly higher and drier areas. On ridges, species of smaller stature that cannot compete with the taller lowland vegetation dominate.
In deciduous forests, the dry, sunny ridges support oaks and hickories, while maple and basswood grow in the moister coves in loamy soil on east and north slopes. Individual trees are spaced according to their canopy size and shape. Between the trees, shrubs may abound or be absent. The distribution of species in the ground layer is dependent on subtle changes in light, slope, elevation, exposure, and soil moisture. In wetlands, sedges dominate the wettest areas, shrubs the intermediate regions, and prairie or woodland plants the drier uplands. Each species occupies its own niche within the community.
The Big Picture
To reap maximum ecological benefits, think of your garden as part of a landscape matrix that connects your yard with your neighbors', one neighborhood with another, and your town with the surrounding countryside. Visualize this matrix as an interconnected web and you can see how each home's landscape has a profound influence on the rest of the natural community.
Within your yard you can create a garden in harmony with its surroundings to keep the matrix intact. Locate lawns close to the house, and plant an area of turf no larger than the space you need for family barbecues or summer games of croquet. This is the part of your yard that will be highest in maintenance and lowest in diversity of plants and associated wildlife. Create a shallow depression where water can infiltrate instead of running off of lawns and paths and eventually into nearby waterways, where it can cause erosion and pollution. Also place ornamental and vegetable gardens near the house, perhaps ring the lawn; consider confining non-native plants to this portion of the garden. If your lot is large, with more space than you need for gardening and recreation, consider a small-scale restoration of the native habitat. You may choose a meadow, prairie, or woodland, based on existing conditions and your region of the country. When linked with wildflower gardens in neighboring yards, these can help reconnect the matrix so that plants and animals aren't trapped in isolated islands in a vast urban or suburban sea.
Next consider the planting design. To start, it helps to visualize a favorite place in the woods or fields and sketch the scene, trying to capture something of the visual quality of the place. If the special place is a woodland, tree trunks will no doubt dominate the picture. In a prairie or meadow, the sea of grasses or scattered clumps of shrubs will create the scene. This exercise will reveal the major structural components and types of plants that give a place its unique character. Understanding this character is fundamental to designing with nature.
To recreate a natural scene in your garden, you must first duplicate or approximate the visual-essence species—those plants that are present in the greatest numbers or that dominate the vertical structure of the plant community. In a woodland it is the tall, dark trunks of trees, those species without which you would not have the woods. To maximize the ecological complexity of your wildflower garden, you must duplicate this vertical structure. Layering adds visual as well as ecological complexity. The canopy creates a monumental feeling. The understory brings the enclosure down to an intimate level, like the ceiling of a living room. Shrubs divide spaces, screen views, and create enclosures. The ground layer, like the furnishings of a room, offers the variety and seasonal interest that all keen gardeners crave.
In a garden modeled on a grassland, tall grasses can take the place of shrubs. These grasses and tall, herbaceous wildflowers are like translucent screens, whereas dense wildflowers, such as cup plants and Joe-pye weed, form solid walls in summer that become see-through in winter.
The wildflower garden does not have to be a reconstruction of nature, however. The design may be highly ordered. A pergola can substitute for tree trunks, with vines forming the canopy. Hedges can be the shrub layer. The point is to represent nature in a form that reflects your individual aesthetic but still functions ecologically.
C. Colston Burrell is a designer, writer, photographer and naturalist. A lifelong gardener and advocate for native plants, he has written and taught about design and plants for over 20 years. He has edited several Brooklyn Botanic Garden handbooks, including Ferns: Wild Things Make a Comeback in the Garden (1994, 1995), The Natural Water Garden: Pools, Ponds, Marshes & Bogs for Backyards Everywhere (1997), Woodland Gardens: Shade Gets Chic (1995), and The Shady r: Knockout Plants That Light up the Shadows (1998). He is the author of Perennial Combinations: Stunning Combinations That Make Your Garden Look Fantastic Right From the Start (Rodale Press, 1999) and the award-winning A Gardener's Encyclopedia of Wildflowers: An Organic Guide to Choosing and Growing Over 150 Beautiful Wildflowers (Rodale Press, 1997). He has graduate degrees in horticulture and landscape architecture. Cole recently moved his garden from Minneapolis to the Blue Ridge Mountains near Charlottesville, Virginia.