Why do we dress in layers? To adapt to changes in the environment, like heat, humidity, or cold. Layers in garden design share the same goal while seeking to delight and connect us with nature.
The inspiration for layered plantings comes from observing natural landscapes where the native landscapes are the shade and texture of the deciduous woods with its understory of flowering trees, and the grassy meadows of savannas, balds, and the coastal plain.
Big strides in ecology have revealed more of the natural processes that give these original landscapes a high degree of beauty and harmony, plus the resilience to thrive without any human help. Plant communities turn out to be a key to success. Plants thrive best and stay healthier growing together in the relationships that have evolved over millennia. Layers are a method to design plant communities into your garden or landscape.
The Functional Layer
The bottom, or functional layer, forms a matrix of companion plants. It is nicknamed “green mulch” as it uses plants to cover the ground. The functional layer handles most of the eco-services that keep the garden healthy. It is visually low key although it comprises about 40 percent of the plants. This ground layer is the perfect place for plants like Lamium or Colts Foot, that thread themselves around other plants to compete for the sun. Grasses and sedums dominate this layer in sunny gardens, while moss, Carex as well as lovely plants like Tiarella and wild Gingers are ideal for shady sites.
In designing the functional layer, what’s happening underground is as important as what happens above. The resiliency of your planting depends on combining a variety of root profiles: taproots, branching, nodal, and others. Native plants often have deeper root runs than exotics, making them ideal candidates for the functional layer. To learn the root profile of a plant, search on Google for “[plant name] botanical drawing”. Look at the images and you will quickly find one that depicts the root profile.
In our gardens today, we use endless mulch around individual plant specimens, thus effectively preventing plant communities from getting established. Instead of mulch, bring in the functional layer of plants and watch the biodiversity increase, the pollinators congregate, and maintenance hours drop to a fraction of what they were.
The Design Layer
The next layer is the design layer, which is probably the most familiar to us. This layer is all about beauty, pandering to our aesthetic delight. Important considerations for the design layer are legibility and staying power. Legibility is a subtle trait. Visitors must recognize your garden as a garden, and not a hodgepodge of plants. The classic design rules work well in this layer: repetition, massing plants, and planting big to small, to name a few. To achieve this, about 40 percent of your plants should belong to the design layer to achieve legibility.
Staying power has two dimensions. Plants need to last a good number of years, staying in the same place to maintain the design. Staying power also refers to the importance of these plants looking good year-round. Hardy perennials are ideal for this layer, along with smaller shrubs and woodies. Success is best achieved by focusing on the structure of plants and their textures.
The Seasonal Thrills Layer
The seasonal thrills layer is where you play with color. A plant in the design layer is chosen for its structure. Take Baptisia for example, which is a lovely, vase-shaped branching plant with good foliage spring and summer, golden color in fall, and slender stems holding the space in winter. In the spring when it flowers, the colorful bloom spikes make this plant join the seasonal thrills layer in your garden.
The Filler Layer
The last layer to consider is the filler layer. It is especially important in beginning a new garden, as it helps cover the ground while the young plants of the other layers are maturing. It is also a way to add spontaneity to the garden. Annuals are very useful plants in this layer, as are short-lived perennials like Columbine, Heuchera, or Astilbe.
How to Plant in Layers
By looking at our garden with these layers in mind, you’ll see immediately which one needs your attention. Improve one layer at a time or spend the winter months designing your plant communities so that you can upgrade all the layers together. If you are starting out from scratch, plan the design layer well and lay those pots out on the bed, add the seasonal layer plants, and then dig in the functional layer around them. Finally, scatter an annual seed mix to create a filler layer. It’s amazing how well seeds germinate if the functional layer is in place.
Planting in layers brings biodiversity and beauty to garden landscapes. Gardens are, after all, made by and for humans to enjoy and connect with nature. Naturalistic plantings bring joy to people and wildlife. Try it and see how they engage people and draw them in.
Featured image: Garden layers at Montrose Gardens in North Carolina / Erica Winston.
Erica Winston is an NGC Landscape Design Consultant and shade gardener. Her own garden is a certified National Wildlife Federation Backyard Habitat.