Planting design can be overwhelming for people. Where do you start? How do you combine plants together?
With naturalistic planting, grouping plants in layers simplifies design. Layers help you think about how plants fill space—not just horizontally, but also vertically. Planting in layers also resembles what we see in wild, healthy ecosystems.
LAYERS IN THE WILD
If you look across a wildscape, you will notice layers of vegetation where there are clear breaks between certain plant types. It may be one, two, three, or more that are visible.
The theory of niche partitioning explains why these layers exist. A niche is the role that an organism has in the environment while considering the resources that an organism uses to survive and its interactions with other creatures. No two organisms can occupy the same niche. For example, low sedges grow along the ground in filtered light while tall perennials soar above.
In plant communities, we see plants have evolved different growth habits to survive in the same space. In Sowing Beauty, James Hitchmough notes two driving factors of why plants grow in layers are their different strategies of light capture and for enhancing the potential for pollination.
The layer of seasonal flowers Castilleja indivisa (Texas Indian paintbrush) and Salvia lyrata (lyre-leaf sage) emerge out of a grassy layer while Baptisia alba (white wild indigo) rises in prominence behind, forming a third layer in this roadside community.
In this bog habitat, Sarracenia alata (pale pitcher plant) grows out of a grassy matrix. Scattered around are woody shrubs beneath a canopy of pines.
Even in this managed pasture, two layers are visible, the grassy groundcover and the emerging Baptisia sphaerocarpa (yellow wild indigo).
THE PLAYERS IN LAYERS
Layers simplify our design approach by allowing us to break the planting into smaller groups.
We need a system to utilize layers in naturalistic planting design. Different practitioners have approached their use of layers similarly but have given them different names. If we look at three different books, Planting: A New Perspective by Piet Oudolf and Noel Kingsbury, Planting in a Post-wild World by Thomas Rainer and Claudia West, and Naturalistic Planting Design by Nigel Dunnett, we can see a model for four distinct layers in naturalistic planting design. They include
primary plants / structural layer / anchors
repeating plants / seasonal theme / satellites
scatter plants / filler plants / free floaters
matrix
The top three in the list above primarily function for beauty and ecology while the matrix serves as a groundcover layer to prevent weed growth.
This table provides an overview of the different names of each naturalistic layer from various authors.
PRIMARY PLANTS / STRUCTURAL LAYER / ANCHORS
This layer provides the dominant presence and aesthetics for most of the growing season in the planting. The plants can be shrubs or small trees, but in naturalistic design big perennials typically fill this role.
The species in this layer are competitors that can achieve size over the growing season and have a presence for several months. Another important aspect is they carry winter interest for the slower part of the gardening season.
Examples include Baptisia alba (wild white indigo), Eutrochium fistulosum (joe pye weed), Eryngium yuccifolium (rattlesnake master), Rudbeckia maxima (giant coneflower), and Panicum virgatum (switchgrass).
Baptisia alba (right) is a wonderful early structural plant at Ephemera Farm. After it finishes flowering, it produces structural seedheads that can last in the garden into winter. On the left is Arnoglossum plantagineum (prairie indian plantain), and while it provides good structure in the spring, it will go dormant in early summer as the stem collapses.
At Chanticleer, Eryngium yuccifolium (rattlesnake master) acts as a structural plant in this planting on the elevated walkway. It starts flowering in the summer, and the seedheads last into winter.
SCATTER PLANTS / SEASONAL THEME / SATELLITES
This layer provides our seasonal interest in the planting. The strategy here is to choose 2 or 3 plants that pair well together in different seasons for around 4–6 waves of color to appear throughout the growing season. These waves are when plants come into bloom at similar times to provide color interest.
Here again I like to think of plants that can provide multi-season interest. For example, Pycnanthemum tenuifolium (narrow-leaf mountain mint) is a lower growing species, but by using it we can have interesting columns of foliage in the spring, flowers in the summer, and seedheads for autumn and winter.
I do like the name satellites, this idea of plants revolving around greater beings of mass in the garden that are anchors. Nigel Dunnett notes that he sites these around the anchors and then has them scattered throughout the planting as singles and groups of three. Others approach this layer considering sociability, a plant’s natural approach to arranging themselves in groups in the wild. There may be groups of 3–20 plants based on what naturally occurs in the wild.
Here’s a list of species I’ve used as season interest here at Ephemera Farm.
March: Narcissus pseudonarcissus (lent lily), Muscari neglectum (grape hyacinth), Ipheion uniflorum (star flower)
April May: Penstemon digitalis (foxglove beardtongue), Phlox pilosa (prairie phlox), Marshallia caespitosa (clumping Barbara’s buttons)
June-July: Pycnanthemum tenuifolium (narrow-leaf mountain mint), Stokesia laevis (Stokes’s aster)
August–September: Gaillardia aestvalis var. winkleri ‘Grape Sensation’ (Winkler’s firewheel), Physostegia virginiana (obedient plant)
October–November: Muhlenbergia capillaris (pink muhly grass), Symphyotrichum oblonigfolium (aromatic aster), Symphyotrichum lanceolatum (panicled aster)
At Ephemera Farm Phlox pilosa and Penstemon species make a wonderful seasonal filler layer.
Verbena bonariensis (tall verbena) and Oenothera lindheimeri (white gaura) make a good seasonal theme layer in this planting in the Tower of London Superbloom.
SELF SOWERS / FILLER PLANTS / FREE FLOATERS
This layer features ruderals that self sow themselves around the garden. These plants don’t last long, and they maybe quite abundant after planting and less years later. But, if bare soil or a disturbance occurs, they will quickly germinate and fill in the gap. You are basically creating your own seed bank in the soil, but instead of it dominantly being weeds it is now attractive plants.
We generally have two periods here at Ephemera Farm where seeds germinate, fall and winter for most cool-season plants and short-lived perennials and spring for most warm season plants.
Fall: Strepthanthus maculatus (clasping jewelflower), Lupinus subcarnosus (sandyland bluebonnet), Trifolium incarnatum (crimson clover), Gaillardia pulchella (firewheel), Nemophila phacelioides (Texas baby blue eyes)
Spring: Gomphrena globosa (globe amaranth), Celosia spicata (celosia), Chamaecrista fasciculata and Chamaecrista nictitans (partridge peas), Cosmos sulphureus (sulfur cosmos)
Lupinus subcarnosus (sandy-land bluebonnet) germinates to fill gaps in my plantings at Ephemera Farm.
Nemophila phacelioides (Texas baby blue eyes) germinates in the fall in disturbed spots and then rewards us with beautiful flowers in early spring.
THE MATRIX
I’m happy that the authors all chose the same name for the groundcover layer. But, I think that’s because of how this layer is primarily functional in nature. The role is to cover the ground to prevent the growth and emergence of weeds.
Carex texensis (Texas sedge), Carex flaccosperma (blue wood sedge), Carex cherokeensis (Cherokee sedge), Sporobolus heterolepis (prairie dropseed) and Eragrostis spectabilis (purple love grass) are a few that I use in this role. However, forbs like Glandularia canadensis (rose vervain) and Conoclinium greggii (Gregg’s mist flower) that spread as groundcovers can also function in this role.
Bulb foliage from Narcissus (daffodil) or Lycoris (red spider lily) can also serve this function, shifting from seasonal filler to ground cover layer later.
Carex texensis (Texas sedge) has become my go to matrix species at Ephemera Farm. It’s native on site and is tolerant of sun and shade conditions.
Echinacea pallida ‘Hula Dancer’ (pale coneflower) and Dianthus carthusianorum (Carthusian pink) emerge from the matrix of Sporobolus heterolepis in Oudolf Field.
PUTTING LAYERS INTO PRACTICE
If you’re starting from scratch, here’s the steps I would take to start developing layered naturalistic plantings.
You first have to know what species will perform well in your area. Visiting arboretea, wild areas, trial gardens, and garden centers is a good start. Many of the plants I now use in my beds were trialed on site for a few years before committing to their use.
Keep a bloom calendar of when plants emerge and go through stages of growth and flowering. Note in your calendar what does well in your area and as well as others in your general proximity. From here you can start to build the timing between plant foliage, flower, fruit, or form.
Once you have a species list, grab pictures you’ve taken or found on the internet and build a mood board. It can easily be done in a word document or slide show app. Consider if there are ways that you can play off the layers colors or textures. For example, when my Joe pye weed blooms, it’s a similar color to the Gaillardia ‘Grape Sensation’ flowers.
An example mood board of the species I rely upon for color at Ephemera Farm. Grouping plants in such a visual pattern allows you to start seeing patterns and combinations possible.
Make sure that plants are compatible with their survival strategy. Competitors can outcompete lower layers.
Consider height. Is everything the same height or is there variation? You are trying to avoid having everything the exact same height; otherwise you will just have one layer. Use references to determine the height. It helps to sketch out the plant height. Or, put the heights into Excel and make a bar graph. Even if you aren’t very good at drawing, just drawing height bars will help you compare how tall they get.
Start simple. For small areas, limiting species diversity is important for greater impact. Too many species in one area will look like a mess. Assuming you have 3 structural plants, 5 waves of 3 seasonal plants (3 × 5 =15), and 2 matrix options, that’s 20 (3 + 15 +2) different plants.
Choose your anchor plants first. Winter interest is one of the most important considerations in design because there will be a few months of the year when these plants are the dominant interest in the garden. And, make sure they can persist even with ice and snow load. While we are mainly focused on perennials, don’t forget that woody trees and shrubs can serve as anchors. Some woody species also can be coppiced to limit their eventual size.
I would argue the next step is to decide on what you want your groundcover layer to be. Some practitioners will cover the site with the groundcover species first to allow it to establish for a few years. This manages the weed growth, and the stress will keep vigorous plants in check. Matrix species generally look better in bulk instead of having one here, one there. It’s helpful to grade between their blocks to slowly shift from say Carex texensis to Carex flaccosperma so they look blended.
Next, fill in with the seasonal theme layer. Consider spacing them in so they appear in groups of 3 to 10 with some sole outliers.
Last, plant or seed in the filler plants so they can fill gaps while the seasonal theme layer is getting established.
After planting evaluation is key. What looks good and what works? You may have to do slight adjustments over the years. But, that’s part of the joy of gardening with layers in naturalistic planting is learning what works together to create a beautiful, ecologically friendly design.
Do you want to learn more about naturalistic planting? Sign up for my waitlist for my upcoming class The Naturalistic Planting Primer. Even if you’re a newsletter subscriber, I’ll send you a special email to remind you when it goes live.
KEEP GROWING
