How it “functions” in the landscape

Story and Photos by Susan Jasan

There is a famous phrase in design: “Form follows function.” More correctly, “Form ever follows function,” which is often attributed to architect Louis Henry Sullivan (1856-1924). In fact, the concept has been debated for centuries, much as the eternal question, “Which came first – the chicken or the egg?” Basically, it is the principle that the shape of an object should be designed based on its use or its function.

Red hot poker (Kniphofia uvaria) is spiky in both flower form and foliage. Contrast it against a fine textured ground cover.

Taking the concept a step further, architect Frank Lloyd Wright (1867-1959) said, “Form and function should be one, joined in a spiritual union.” 

For this writer and designer, when considering plant selection for a landscape, it seems prudent to fully consider the form of a plant as one considers the function it will serve in the landscape, as Frank Lloyd Wright said, “joined in a spiritual union.”

Black Lace elderberry (Sambucus nigra ‘Eva’) has a very upright loose form.

Equally so, one must also consider the environment in which the plant will live: light exposure, water, soil nutrients, or lack thereof.

The ‘Mother Lode’ juniper (Juniperus horizontalis ‘Mother Lode’) demonstrates a low, prostrate, spreading form. Many horizontal junipers are great ground covers for full sun.

But even as one reflects on the function a particular plant will serve in the landscape, whether a foundation planting, a specimen plant, for color or fragrance, or simply for fun, one is also profoundly struck by the reality that a plant’s form in and of itself typically makes the strongest statement in the landscape. Form quite simply is the three-dimensional shape of the object and leaves a lasting impression.

‘Wind Dancer’ love grass (Eragrostis elliottii ‘Wind Dancer’) is true to its name as it indeed dances in the wind. Note the tall form of American arborvitae (Thuja occidentalis) in the background. The contrast complements both.

It’s not unlike the adjectives we use to describe the human form: One person might be tall, another short, another round, another husky. And so it is with plants. Trees and shrubs are typically categorized as columnar, compact, conical, a cordon, mounding, rounded, globe, broad, weeping, spreading, arching, oval, narrow, vase, pyramidal, pleached, upright, spiral, espalier, irregular, or even topiary. Ground covers too have a great variety of forms and are often described as clumping, matting, sprawling, spreading, or spiky.

The upright pyramidal forms of these ‘Green Giant’ arborvitae (Thuja ‘Green Giant’) clearly define the limits of the garden and help frame the walkway.

How does one know what form to use in what application in the landscape? Part of the decision is personal taste, part of the decision is based on the function the plant will serve, and part is determined by the plant’s relationship to others in the design. Using a massed area of one form can create continuity or monotony, depending on one’s perspective. And be assured neither view is right or wrong. Using a single specimen with a strong form can be an effective means of developing a focal point when contrasted against plants of a differing form.

First Snow spirea (Spiraea x cinerea ‘Grefsheim’) demonstrates a weeping form against the backdrop of the crabapple tree (Malus spp.). Without its blooms, the spirea will appear broader and rounder.
This agave in the desert presents with its dramatic spike form enhanced by the play of light on its leaves.

Remember too that though a certain plant may have a “typical” form, sometimes cultivars within a genus or even within a species have very unique forms. For example the typical maple tree, such as a red maple (Acer rubrum) has a broad form. An Armstrong maple (A. x freemanii ‘Armstrong’, has a relatively narrow form. And in further contrast, the Amur maple (A. ginnala) has an upright form that is rounded or broad at the crown. So, if there is a certain type of plant that you like, but the natural form is not quite what you want in a particular space, look to see if there might be other cultivars that better fit the application you desire.

Structures and hardscape features in a landscape can also present a strong form. This rectilinear screening provides a framework for vines and creates an enclosed space within the garden.
One only need think of a desert scene, and the impact of the form of plants is apparent, recollecting the classic form of cacti.

One significant caution in regard to plant form: If you are trying to shape or prune your plant into a form that is not its natural growth form, the plant will continue to try to grow back to its natural shape. In this circumstance, you are better off selecting a different plant that can give you the look you want.

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