When someone buys a plant, they often do so with a specific site in mind. It could be a large pot by the front door that needs filling, or a dead shrub elsewhere that needs replacing. Plants are often purchased in a vacuum with only a specific site or purpose in mind and without consideration of how a plant will pair with the others around it. Having the flair to choose a plant knowing how it will blend or clash with the plants around it is part of what makes a proper gardener. Having the foresight to understand how this will change over the course of the season and in subsequent years makes an even better gardener.
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Physocarpus Foliage
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Juniper Foliage
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Juniper and Physocarpus Pairing
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Cercidiphyllum Foliage
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Cercidiphyllum and Weigela Pairing
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Weigela Foliage
My supervisor, Richard Hawke, runs the Plant Evaluation Program at the Chicago Botanic Garden. He has published dozens of articles covering different plant genera and has shared that many gardeners simply want to be told which cultivars are best in each trial. I think this notion would carry over to nurseries and garden centers when it comes to selecting plants. I can personally attest to this, as I’ve gone to The Home Depot and local garden centers with friends who look at me once we arrive and ask, “What should I get?”. For people who aren’t into plants, these places provide very little guidance.
As if to stifle creativity, plants are often organized by broad categories like shrubs, perennials, and annuals, then alphabetically. Some nurseries have a designed display near the entrance to welcome customers, but beyond this, plants are typically laid out in a rather bland fashion. This may help experienced gardeners find what they want as quickly as possible, but it does little to educate rookies on garden design. Signage may suggest different plants that can be paired to achieve an effect, but without seeing the plants together, this is hard to visualize and harder to sell as a design.
If you’re fortunate enough to have a local retailer that offers plants in a more cohesive layout, consider yourself lucky. Some nurseries are wise enough to incorporate display gardens into their retail spaces to help customers visualize what can be done with the nursery’s offerings. I wouldn’t expect nurseries to change their layouts to a jumbled mess of desirable groupings, but perhaps something like brochures could be offered to educate folks on how to better navigate a nursery and select a harmonic array of plants. For now, though, we’ll have to develop an understanding of plant pairing on our own.
In my opinion, plant pairing should be based on foliage and habit, as flowering is often too ephemeral to be a priority. With many perennials and woodies blooming for less than a month, flowers of two different species may only bloom synchronously for a couple days or weeks, if at all. Of course, the flowers of one plant may combine well with the foliage of another, but this is still short-lived relative to the entire year. Foliage, on the other hand, lasts for multiple seasons. Habits also last for months, if not the entire year in the case of most woodies. Advanced gardeners could even consider the traits of different plants’ bark when pairing to enhance their garden’s winter interest.
When it comes to foliage, color and texture define how we perceive a plant, with the latter consisting of size, shape, and density of the leaves. The narrow leaves of grasses have a fine, feathery appearance, while the dense, broad foliage of hydrangeas gives a strong and sturdy impression. Thanks to modern breeding, leaves come in just about every color imaginable and can evoke a myriad of emotions. The number of trait combinations you can have across these variables feels infinite, but this gives us more variation to play with and gives each garden a unique appeal.
Habit plays into how foliage is presented, with a plant’s stems largely determining its personality. Erect or fastigiate plants often have a weighty attentiveness, resembling the King’s Guard in England. Plants with cascading stems often resemble fireworks and seem energetic. Groundcovers that slink along the ground present a more melancholic tone. In some cases, multiple habits can be found on the same plant. Many Ajuga cultivars, for example, have a prostrate habit with their vegetative growth and an erect habit with their inflorescences. While my interpretations above are highly subjective, I believe plants will inevitably speak to different emotions based on their leaves and habits.
On a more objective note, several factors need to be considered when selecting and siting plants. First is how traits change over the course of the growing season. A plant’s habit can change more than one would expect, especially when transitioning between vegetative and reproductive growth. Leaf color also frequently changes from summer to fall (sometimes from earlier in the year as well).
Second, a plant’s preferred growing conditions must be considered. It may be foolish to pair plants with drastically different sun, soil, or water preferences, but differences can be managed by gardeners during and after planting. If a gardener can’t manage these differences in the long run though, it’s best to choose plants that would like to be treated the same. Larger plants in a group can also influence the microclimate of smaller plants. For example, a large shrub positioned directly west of a smaller perennial shields the perennial from afternoon sun and decreases its demand for water.
Third, positioning should not be overlooked in plant pairing, especially when two plants have vastly different sizes where one can completely obscure the other depending on the viewing angles. From one perspective, for example, someone may see what appears to be a standalone shrub, but a vigorous groundcover may be visible beneath this shrub from a second perspective.
One final thought: while it may be tempting to have many sharp contrasts, maintaining continuity through a garden is important. A cacophony of contrasting colors and textures will make a garden seem chaotic and poorly planned. It is therefore best to keep contrasts to focal points.
The photos in the slideshow above are plant pairings in my own garden. The garden was planted this spring and plants are spaced with their final sizes in mind. As such, the plants appear sparsely spaced for now, but will fill in during the coming years to make proper pairings.
Physocarpus opulifolius ‘Tiny Wine’ and Juniperus virginiana ‘Grey Owl’: Contrasts abound between these two plants, which will become more obvious as they grow towards each other. The ninebark has three-lobed, bronze-burgundy leaves, while the juniper has scale-like silver-green foliage. The colors of these plants change little over the growing season, so they will remain starkly different. The ninebark will reach nearly twice the height of the juniper, with the latter spreading more horizontally. Regardless, these plants are nearly parallel to the nearby sidewalk and can be seen together from both the sidewalk and the house.
Weigela florida ‘My Monet Purple Effect’ and Cercidiphyllum japonicum ‘Red Fox’: The contrast between these plants is significant but less prominent than in the previous example. The weigela is a short, dense, mounding shrub with green lanceolate leaves with white variegated margins and a subtle purple cast. The Cercidiphyllum is a somewhat columnar tree with dark red-purple cordate leaves in the spring that age to blue-green in summer. ‘Red Fox’ towers over the weigela from the west, sheltering it from afternoon sun, which is often desirable for cultivars with variegated foliage. Though these plants have greatly different habits and sizes, their foliage colors differ more subtly and should continue to do so as the Cercidiphyllum leaves change.