Future Viable Plant Palettes for Metropolitan Areas, Part 10

Figure 1: BRIT bioswale 2 polyculture in July 2016 after weeding and mulching have brought the planting back closer to the original design intent shown in lead image from part 8. The bioswale is now ready for hundreds of additional specified plants that will be installed in the fall once the weather cools down. image: design and photo by David Hopman

Figure 1: BRIT bioswale 2 polyculture in July 2016 after weeding and mulching have brought the planting back closer to the original design intent shown in lead image from part 8. The bioswale is now ready for hundreds of additional specified plants that will be installed in the fall once the weather cools down.
image: design and photo by David Hopman

Polyculture Maintenance and Plant Palettes

This post is about the maintenance decisions that can have a profound effect on the range of plants useful for an aesthetically qualified urban polyculture. Some of the issues are addressed in the spreadsheet that was presented in part 8 of this series. For example, relative aggressiveness will help determine if plants play well together or if one plant is almost sure to dominate. However, the discussion that follows is on factors affecting plant palette decisions that go beyond the intrinsic characteristics of each plant that is considered.

Pruning

Polycultures of herbaceous perennial plants and grasses are low maintenance but will frequently be more useful for aesthetically qualified native urban polycultures if they are pruned two or three times a year. Just because a plant is native does not mean that it must be allowed to express only its non-maintained form. This is especially true when soil amendments and irrigation are used. Water, fertilizer, and soils that are richer than what the plant would normally grow in without human intervention tend to make the plants taller, fuller, and more aggressive than otherwise, and may even cause them to flop over, particularly when they are blooming. Selective pruning may actually bring their appearance and stature back closer to a “natural” state.

Another big advantage to selective pruning is that it broadens the range of plants that can fit the aesthetic criteria of a particular polyculture. For example, one of the best native plants we have for shade conditions in North Texas is Inland Sea Oats (Chasmanthium latifolium). It is tolerant of both drought and seasonal inundation, stays attractive throughout the year, and establishes and spreads very easily. However, with irrigation it can easily get 3-4 feet tall, which may not be a desirable trait in an urban polyculture where other lower plants could have a seasonal focus. By cutting Sea Oats in half early in the season, it can easily be maintained at 18 inches tall. Some of the plants can also be left taller as “scatter plants,” which is how we are maintaining the UT-Arlington polyculture featured in part 7 of this series.

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Future Viable Plant Palettes for Metropolitan Areas, Part 9

Figure 1: Knee high grass polyculture in full sun designed for BRIT ecological detention structure. design and image: David Hopman

Figure 1: Knee high grass polyculture in full sun designed for BRIT ecological detention structure.
design and image: David Hopman

Assembling Polycultures from a Qualified Palette

Part 8 of this series detailed the rationale and methodology for extracting qualified native plant species for use in creating polycultures. This month’s post features a discussion of how to successfully combine the species into a low maintenance native polyculture that can take the place of a monoculture groundcover.

The 109 species selected for use in part 8 were sorted to find groupings unified by height, texture, line, color, or form. Two categories of plants were created for each of the main polycultures. The first is very aggressive groupings of lower plants that serve as the primary intermingled groundcover. The second group of plants for each polyculture are accent plants that are unified with the lower grouping by texture, line, color, or form, but also have a strong contrasting element that will show them to best advantage. These are either more transparent scatter plants or more opaque shrubby plants used more like rocks or small hill shapes.

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Future Viable Plant Palettes for Metropolitan Areas, Part 8

Figure 1: Design and Photoshop mockup of Sun-Juncus polyculture and low polyculture edge for bioretention structure at BRIT. Lower left shows existing plants being killed by solarization. Design and image: David Hopman

Figure 1: Design and Photoshop mockup of Sun-Juncus polyculture and low polyculture edge for bioretention structure at BRIT. Lower left shows existing plants being killed by solarization.
Design and image: David Hopman

Case Study: Extracting native polycultures for bio-retention structures at The Botanical Research Institute of Texas

Reconceptualizing a Plant Palette Using Native Polycultures

Part 7 of this series focused on small steps that can be taken by any planting designer that will gradually move their designs in the direction of aesthetically qualified native urban polycultures. This post begins the discussion of a more complex and rigorous approach that I used in North Texas. The complexity of the Dallas/Fort Worth/Arlington area of North Texas is confounding when considering the use of extracted native polycultures as design components. It is a sprawling and rapidly growing metropolitan area of more than seven million people that is larger than the state of Massachusetts.

The problems and opportunities associated with reconceptualizing nature in this non-temperate area clarify an understanding of the issues in other areas where integrating nature may not be quite as complex and problematic. A detailed discussion is presented below that illustrates a research methodology used to develop 10 contrasting native polycultures for ecological retention structures on the campus of The Botanical Research Institute of Texas (BRIT) in Fort Worth, Texas.

Using Research to Define Aesthetically Qualified Native Urban Polycultures in North Texas

In North Texas, as in many other areas of the United States, the information needed to extract a wide range of native polycultures is simply not available. Academics and research institutes have a unique role to play in developing this information as the following description demonstrates. This research is directed at a palette of plants for ecological retention structures (large scale rain gardens), but can also serve as a model that can be adapted for the plant palettes required for many other types of planting design in metropolitan conditions in the Great Plains of the United States and other biomes throughout the world.

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Future Viable Plant Palettes for Metropolitan Areas, Part 7

Figure 1: Simple low woodland polyculture in spring (April 12) at Hopman residence in Arlington, Texas. Woodland Phlox (Phlox divaricata), Wood Violets (Viola missouriensis), Cedar Sage (Salvia roemeriana), Horseherb (Calyptocarpus vialis), and Golden Groundsel (Packera ovata). image: David Hopman

Figure 1: Simple low woodland polyculture in spring (April 12) at Hopman residence in Arlington, Texas. Woodland Phlox (Phlox divaricata), Wood Violets (Viola missouriensis), Cedar Sage (Salvia roemeriana), Horseherb (Calyptocarpus vialis), and Golden Groundsel (Packera ovata).
image: David Hopman

Beginning the Transition to Native Polycultures

Developing a Plant Palette that Balances Aesthetic Control, Environment, and Ecology

Developing a plant palette for metropolitan areas that moves beyond the native and adapted plant palette is a very challenging and necessarily a very long term proposition. The vast corporate, design, regulatory, and research infrastructure that has evolved to the current state of the art will change very slowly, as it has in the past. As with any innovation, it will first be seen as radical and even eccentric and there will be many stakeholders that will push back hard against the tide of change. There are a number of possible scenarios for moving forward towards a more resilient and ecologically and environmentally supportive landscape palette.

One likely scenario for the transition to a more balanced palette is an incremental approach that gradually introduces native species, varieties, and selections into the infrastructure of the green industry. This would be an evolution of the ‘native and adapted’ palette that has been  emerging since the 1980s, perhaps accelerated by climate change and the ‘new normal’ of warmer conditions with wide swings in rainfall patterns, coupled with increasing water needs from a rapidly growing population. This evolving palette will represent the same basic approach currently used by many designers for the selection of plants. Designers will search for aesthetically pleasing groupings, or drifts, of discrete monocultures that meet the practical, aesthetic, and financial criteria desired, albeit in a more environmentally and ecologically sustainable way.

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Future Viable Plant Palettes for Metropolitan Areas, Part 6

Figure 1: Unmowed HABITURF® at the Bush Presidential Center in Dallas, Texas image: David Hopman

Figure 1: Unmowed HABITURF® at the Bush Presidential Center in Dallas, Texas
image: David Hopman

Part 6: Native Plant Turf Polycultures

Part 5 of this series introduced three relevant strategies at the new George W. Bush Presidential Center that were employed to select future viable species of plants. The first two, using local plant consultants and recreating a local prairie ecosystem, are addressed in part 5. This month’s post will focus on the third strategy, using an aesthetically qualified native polyculture for large areas of turf at the Bush Center.

The idea of using a palette of indigenous (actual native) plants is currently largely the purview of a small, relatively sophisticated cadre of native plant specialists and enthusiasts. Reconciling two points of view—the desire to restore complete ecological ecosystems with their environmental and ecological benefits, and using native and other adapted plants with a more traditional design approach, requires a reconceptualization of natural plant communities within a cultural context.

This difficult problem must first be addressed at the macro scale by finding the most appropriate native ecosystems, within the overall biomes, that are most practical and useful for the extraction of species for a new environment, the ‘new nature’ created by development conditions in metropolitan areas. It must then be addressed at the micro scale by constituting the details of this new synthetic environment, the particular plant palette, so that it meets biological, cultural, personal, and environmental goals and achieves a better balance of the three areas of aesthetics, environment, and ecology. The native turf polyculture used at the Bush Presidential Center is a good example of using both of these strategies.

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Future Viable Plant Palettes for Metropolitan Areas, Part 5

Figure 1: Bush Center south Terrace on opening day in 2013 image: David Hopman

Figure 1: Bush Center south Terrace on opening day in 2013
image: David Hopman

Part 5: Lessons from the Bush Presidential Center: Local Consultants and Urban Prairies

The G. W. Bush Presidential Center landscape is a good point of departure for a discussion of a variety of strategies for future viable plant palettes, as there were three relevant strategies employed for selecting plant species:

  1. Using local consultants to check species for regional appropriateness,
  2. Recreating a local prairie ecosystem in an urban context using ecological restoration consultants, and
  3. Using an aesthetically qualified native polyculture.

The Bush Center is a 23-acre campus near downtown Dallas that features four distinctly different plant palettes. Almost the entire campus, designed by Michael Van Valkenburgh Associates, Inc., was designed with sophisticated sustainable strategies. A small internal Rose garden, however, uses a more traditional green industry plant palette and demonstrates a good balance of a small area of resource-intensive exotic species within a large, biologically diverse, resource-efficient landscape—with many species of native plants.

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Future Viable Plant Palettes for Metropolitan Areas, Part 4

Figure 1: Subdivision entrance planting design using a native and adapted plant palette image: design and computer model by David Hopman, ASLA, PLA

Figure 1: Subdivision entrance planting design using a native and adapted plant palette
image: design and computer model by David Hopman, ASLA, PLA

Part 4: Contemporary Native and Adapted Plant Palette

The rise in research and the popularity of using native and adapted plant palettes can be traced to the work of the Colorado Water Board in the early 1980s. They coined and copyrighted the term ‘xeriscape™,’ a combination of the word “landscape” and the Greek word “xeros,” which means dry. [1-2] Other terms have been created for similar approaches in other areas. In North Texas the term used by the North Central Texas Council of Governments is ‘Texas SmartScape™.’ According to their website, the program is designed to “Conserve water and save $Money$ on your water bills; beautify your home and local environment; attract native butterflies, hummingbirds and other wildlife; and prevent / help reduce storm water pollution!” [3]

The native and adapted plant palette has made a large improvement to the environmental cost/benefits ratio of using plants for ornamental horticulture. The prime driver has been water savings, a subject that many people can relate to, including people who are not focused on other environmental issues or who may be primarily looking to save money and reduce maintenance. The gardening approach using this palette is flexible and can even approach fine gardening standards while using far less resources. The focus of designs using these plants is usually still discrete monocultures, or ‘drifts,’ of single species of plants using unity and contrast techniques derived from traditional principles. There has been a trend in recent years towards more naturalistic intermingled plant combinations using this palette as well. It has been very well promoted by government, industry, the design community, and academia, thereby hastening the adoption of this important innovation. Plants that were very hard to find and very expensive a few years ago can now be found at very low prices in many big box retailers.

The native and adapted plant palette is currently the state of the art when it comes to a proven and commercially-viable environmentally friendly strategy for selecting plants. It is the one that the most forward thinking landscape architects and garden designers use. Some of the tenets have even been written into landscape ordinances in drier parts of the United States. It is flexible, cost effective, and there is ample information easily available to train designers for success.

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