Future Viable Plant Palettes for Metropolitan Areas

Crystal Canyon entrance garden in Arlington, Texas. Grasses installed by landscape architecture students from The University of Texas at Arlington and wildflowers compost seeded in. Photo taken in June of 2013, one year after installation. image: David Hopman
Crystal Canyon entrance garden in Arlington, Texas. Grasses installed by landscape architecture students from The University of Texas at Arlington and wildflowers compost seeded in. Photo taken in June of 2013, one year after installation.
image: David Hopman

Part 1: Aesthetics, Environment, and Ecology in the Creation of Plant Palettes

Essays about plants usually focus on specific plants, specific approaches to combinations of plants, practical uses for plants, plants for specific habitats, etc. These essays are indicative of the broad and continually evolving way that landscape architects approach planting design. This post takes a step back to address the issue of how landscape architects should use a clear set of principles to inform their palette of plants. By thinking first about the plant palette, new approaches to planting design will emerge that reflect the contemporary concerns of both the profession of landscape architecture and society at large.

Many design firms have design priorities that can be summed up in a few words. The ideas are sometimes illustrated with Venn diagrams and referred to as a triple (or quadruple) bottom line. The three criteria that are the focus of this series of posts are aesthetics, environment, and ecology. Other important elements, such as community and economics, can be addressed with a plant palette that balances these three important criteria. However, if art or economics, for example, are the driving generators of a plant palette, it may not be possible to bring the plants into balance with environmental and ecological concerns. Ecology is the most difficult and complex parameter to bring into balance and is currently the leading edge of future viable planting design innovation for landscape architects.

A variety of approaches to the selection of plants will be tested against the criteria of aesthetics, environment, and ecology in future posts. These posts will begin with a critique of palettes that are the most out of balance and proceed to others that gradually bring the three elements into equilibrium. The end of the series will propose a methodology for creating a palette of aesthetically qualified native polycultures suitable for the typical kinds of projects undertaken by landscape architects in metropolitan areas.

image: David Hopman
image: David Hopman

Aesthetics, Environment, and Ecology in the Creation of Plant Palettes  

A brief description of the three areas of aesthetics, environment, and ecology will help clarify how they are used to analyze selection criteria for plant palettes as the series progresses. A broad definition of experiential aesthetics is utilized for this series, summarized by John Dewey as “The enhancement and intensification of everyday experience.” This broader definition encompasses all the criteria that effect human experience and does not focus more narrowly on formal principles and visual models. Planting design aesthetics are often understood through the lens of time-honored design principles that have been used by landscape designers for millennia and are codified in many planting design books. The formal principles of balance, texture, form, scale, color theory, line, and many others are addressed briefly but are not the focus of this series. The broader definition of experience can be summarized as environmental psychology, cultural influences, personal growth and creativity, and the complex human responses to nature and natural systems. Aesthetics are often the main focus of plant palettes because they are an easy sell for both landscape architects and for clients. The pure imageability and experience of aesthetics sells design services and frequently defines the perceived success for both the clients and for the end users of newly constructed landscapes.

The second category, environmental issues, has been elevated as a design criteria to an unprecedented extent in recent years. Phytoremediation of air and water, reducing potable water use, increasing carbon sequestration and reducing the carbon footprint of landscapes, reducing the use of synthetic fertilizer, pesticides, and fungicides, and many other criteria that affect the quality of air, water, and climate change are directly impacted by plant palette decisions. Saving water, saving energy, and air quality are easy to understand and have direct economic impacts that are facilitating the implementation of plant palettes that respond to these important imperatives. Even in geographical areas not generally recognized as environmentally progressive, well adapted plants that save resources are rapidly making their way into the horticulture industry. For example, in North Texas it is very easy to find Salvia greggii (Autumn Sage) in big box hardware stores. This very drought tolerant sub-shrub, native from the Texas Hill Country to the Big Bend area of West Texas, was only available in expensive specialty nurseries as recently as the 1990s.

Ecology is by far the least addressed and understood of the three elements under discussion and can be rightly labeled an even more inconvenient truth. A concise definition comes from the Cary Institute: “The scientific study of the processes influencing the distribution and abundance of organisms, the interactions among organisms, and the interactions between organisms and the transformation and flux of energy and matter.” The challenge for landscape architects is to bridge the divide between well-established ecological systems in undesigned areas and the imperatives of development in metropolitan areas that are the focus of most of the profession of landscape architecture. Another challenge is to learn from ecologists and other natural scientists so that we can combine their knowledge and commitment to ecology with our understanding of human systems and aesthetics.

A new focus on ecology will help metropolitan areas from becoming vast kill zones for the huge variety of flora and fauna that thrived before settlement. It will also help prevent the disruption of complex biotic relationships that we may be only dimly aware of. For example, there have been a number of studies in recent years that show that the Western Fence Lizard (Sceloporus occidentalis) is an incompatible host for Lyme disease and actually removes it from infected ticks. The multifarious interactions between ticks, Fence Lizards, and the environment that creates a healthy lizard population is a small subset of the potential for unintended consequences that can arise from the almost total destruction of ecological systems in metropolitan areas—an unfortunate and frequent outcome of landscape development.

Microflora are another ecological concern getting increasing attention from a variety of disciplines. Doctors are beginning to focus on the relationship between the human biome and health effects ranging from childhood obesity to ear infections. Landscape architects are also studying and implementing practices that promote the benefits of healthy colonies of microflora in soil. Eliminating the use of synthetic fertilizer and pesticides, mitigating compaction caused by construction practices, reducing overwatering, and proper selection and maintenance of native species are just a few of the factors that can lead to a healthy and productive food chain in the soil. The microbiome that begins with bacteria and fungi and moves up through protozoa, nematodes, earthworms, arthropods, and finally to birds and mammals is increasingly being understood for its contribution to the resource efficiency and long term viability of landscapes. This deepens an awareness of ecology beyond the populist realm of birds, butterflies, and bees that are often the focus of information about fauna in horticulture information sources.

A greater emphasis has been placed on ecology in the brief description of the three areas under consideration because it is the area that is most frequently a very low priority in plant palette decisions. It is a tremendous challenge to reconceptualize a plant palette that brings the three areas into a better balance—a new plant palette that mandates a rethinking of the ‘cultural rules’ that continue to drive planting design in the profession of landscape architecture and also requires a carefully considered reconceptualization of ‘urban nature.’ As the series develops, I will explain in detail a proposed methodology that can be used to create this new palette, its benefits, and how it can be a way forward towards a better balance of the three areas.

Part 2 of this post will discuss the problems associated with an unbalanced ‘fine gardening’ plant palette that has a narrow focus on aesthetics. In subsequent months, other approaches will be presented that slowly move towards a better balance of aesthetics, environment, and ecology. The rationale for native polycultures, the aim of this series, will unfold as the problems inherent in other approaches to the creation of plant palettes are detailed.

For more information, see the American Association for the Advancement of Science (AAAS)’s recent EurekAlert! news release, and a video about a polyculture we installed at UT-Arlington in November:

David Hopman, ASLA, PLA is an Associate Professor of Landscape Architecture at The University of Texas at Arlington, a registered landscape architect, and a research associate at The Botanical Research Institute of Texas (BRIT). 

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