by Dan Greenberg, ASLA
See Part 1 and Part 2: An Emerging Meadow, in case you missed the previous installments in this three-part series.
After an exciting spring establishing the meadow grasses, summer’s heat arrived in July. The plants in the upper meadow appeared to take this in stride, continuing to push their foliage taller. In several areas the crowns began to overlap and hide the ground below. It was so exciting to see my meadow taking shape!
by Dan Greenberg, ASLA
Check out Part 1 in case you missed last week’s opening installment in this three-part series.
The winter was a difficult wait. I had planted 400 square feet of meadow grasses, and an additional 600 square feet of soil lie dormant under cardboard and wood chips. I felt a lot like I did years ago watching my baby daughter sleep—desperately wanting to enjoy her company, but knowing that her rest was best for everyone. My plugs were resting.
The wait wasn’t long. Our winter was warm and wet, so signs of life appeared in late February. It was exciting to see bright green blades pushing through the stiffer stems of last year’s growth! It was also startling, as vigorous weeds took advantage of the plugs’ fertile soils. Chickweed, Bittercress, Henbit, and Deadnettle Lamium (clockwise from top left in the photos below) sprung from every planting hole.
by Dan Greenberg, ASLA
My meadow is modest by most design standards. But it’s an awesome 1,000 square foot experiment that is already welcoming birds every day.
How awesome? In one Raleigh, North Carolina, growing season, measured from April through November, and compared against the lawn industry’s standard practices for managing a healthy turf lawn, my meadow saved over 10,000 gallons of water, 6 gallons of gasoline, some engine oil, 8 pounds of lawn seeds, and 9 pounds of fertilizer / pre-emergent herbicide. It also saved me 30 hours of boredom, walking back and forth with a mower or a seed spreader.
My anticipation is already building for next year. The established grasses will grow larger, shade more weeds, and welcome more creatures. And my role will change from a farmer to a steward, a master to a friend.
This meadow is special to me for a number of reasons. I love nature and this brings a piece of it closer to my life. It lets me walk my talk as an environmentalist and landscape architect. And it eliminates a lot of wasted time and resources.
by Wanting Zhang, Student ASLA, and Yiwei Huang, Ph.D., SITES AP, ASLA
Interviewee: Mark Jirik, PLA, ASLA, LEED AP, Certified Arborist
Interviewers: Wanting Zhang, Student ASLA, and Yiwei Huang, Ph.D., SITES AP, ASLA
We recently had a special opportunity to speak with Mark Jirik (M.J.), the Director of Horticulture at site design group, ltd. (site), who provided a lecture to our undergraduate class in Landscape Architecture at Purdue University. This article compiles key insights from his talk and additional reflections he shared with us afterwards. This interview article aims to bridge a gap between theory and practice, providing young designers with an invaluable perspective on designing children’s outdoor environments, especially with planting design, in the Midwest region.
What projects have site worked on previously related to children’s outdoor environments?
M.J.: site has worked on a wide range of park and playground designs for various age groups. A couple of completed projects that come to mind include Seneca Park (2021) located Near North Chicago and the Comer Children’s Hospital Play Garden (2018), also located in Chicago. Seneca Park hosts two playgrounds, one for children ages 2-5 and another for children ages 5-12. Both playgrounds reference the local dune landscape and nearby Chicago landmarks with a variety of both more traditional and creative play opportunities. Comer Children’s Hospital Play Garden, winner of the 2019 ILASLA Honor Award, provides a place of refuge and healing for hospital patients from and is designed to accommodate and be enjoyed by children of all physical abilities.
by Jane Beggs-Joles, Corporate ASLA
It’s August 2023, and growers are deciding on their inventory for 2025.
You read that right: two years out. That’s the best-case scenario, and that’s for flowering shrubs. Sure, perennials will have a quicker turn-around, but trees take even longer. And that two-year forecast? It’s for a three-gallon container. If you like five- or seven-gallon specimens, the timeline gets even longer.
Here are the details:
Right now, growers are looking at what sold this spring and anticipating what will sell through the rest of the year. This tells them both what plants are popular and how much space they have for new crops. They do some math, make some educated guesses about demand, and then order their starter plants (liners) for delivery in spring 2024. Most of those flowering shrubs will need at least a year to grow to a finished size, and that’s how we get all the way to 2025. For slower-growing plants and larger specimens, it will take even longer. If they can’t get the liners until summer or fall, add another few months to the schedule.
by David Hopman, ASLA, PLA
All cities in the United States have undesigned areas that develop what is called “spontaneous urban vegetation”—plants that establish themselves without human intervention or planning. These areas can be large, such as abandoned or vacant building lots, former farms and ranches, and river corridors. They can also be small opportunities for plants and plant communities in sidewalk cracks, between paving and buildings, or anywhere enough soil has accumulated to allow the sprouting of seeds, as was the case on New York’s High Line elevated railroad before it was so famously developed into the urban amenity it is today.
In well-developed cities, 5-10% of the total vegetation or more can be spontaneous. In Detroit, the amount of area abandoned to this undesigned vegetation is about 40% as the city has depopulated and thousands of homes have been removed.
Spontaneous urban vegetation has been widely touted by scientists and landscape architects for its environmental benefits that include but are not limited to:
However, there has been very little discussion, or appreciation, of the role that this vast amount of urban vegetation can have on native pollinators.
by Jodie Cook, ASLA, SITES AP
As a horticulturally obsessed landscape designer for most of my adult life, I’ve observed how our landscape irrigation practices, tools, and technologies have evolved over time. In the last few decades, we have radically changed our plant irrigation practices in public and private designed spaces, particularly in the West. While using a plant palette of so called ‘drought tolerant’ species, many large commercial landscapes, and managed communities such as mine, irrigate four times per week or more in a climate that has never experienced rain with such frequency. How many regions do experience this frequency of natural rainfall? I have often wondered, why do we irrigate non-lawn areas so much?
So, I was thrilled to be a participant in the Climate-Ready Landscape Plants trial evaluations at the University of California South Coast Research Center fields in Irvine, California. I was there, clipboard in hand, as a plant performance evaluator and was not involved in the research in any other way. I did, however, discuss the research at length with those who devised the trial. It was fascinating and eye-opening.
by the Transportation PPN leadership team
For the 2021 ASLA Conference on Landscape Architecture, the Transportation Professional Practice Network (PPN) teamed up with the Planting Design PPN to engage in a lively campfire discussion about planting design for pollinators.
Pollinator planting has been and remains a hot topic (see the December 9, 2021 Field post by Liia Koiv-Haus, ASLA, “Making Space for Pollinators,” and “Roadside Realm” from the March 2021 issue of Landscape Architecture Magazine). Both PPNs agreed that preserving pollinator habitat is important, but the methods and resources used to create habitat differed. This is due, in part, to the landscape scales in which each PPNs’ members typically practice. Other differences included maintenance abilities and strategies, budgets, and “owner” motivation. Planting design practitioners are often hired by property owners intent on creating habitat; transportation practitioners are usually required to justify spending public dollars on habitat creation and not on other, more easily justifiable, competing interests (such as roadway improvements and accessibility).
Transportation PPN leaders started the discussion by outlining federal and state resources that departments of transportation (DOTs) use to inform policy and practice decisions about pollinators. The U.S. Department of Transportation Federal Highway Administration’s Pollinators and Roadsides: Best Management Practices for Managers and Decision Makers is the primary reference for state transportation agencies. The document elaborates on a variety of techniques used by state DOTs, four of which also appeared in Liia Koiv-Haus, ASLA’s “Making Space for Pollinators”—altered mowing practices, reduced herbicide use, protection of existing stands of native vegetation, and re-seeding efforts post construction.
by David Hopman, ASLA, PLA
There is an ongoing debate in the landscape architecture profession between plants as structural and amenity elements, primarily for human enjoyment and services, and plants that perform these vital human functions while also supporting the complex ecological relationships in a local biome. Sara Tangren and Edward Toth of the Mid-Atlantic Regional Seed Bank (MARSB) have contributed very valuable research-based information to this debate in their new report Native Plant Materials Use and Commercial Availability in the Eastern United States.
The report is the result of a survey of native plant material users from across the entire Eastern United States, with 760 respondents, and includes written comments. The respondents are drawn from NGOs, government, and commercial entities involved in ecological restoration projects and native plant production.
Amidst gradual reopening in parts on the world, the COVID-19 pandemic continues to affect nearly every aspect of life, from personal interactions to business to learning to recreation. The American Society of Landscape Architects (ASLA) is sharing insights, observations, and impressions from ASLA members based around the country here on The Field. In recent weeks, we’ve shared updates and resources curated by the Community Design, Historic Preservation, and Children’s Outdoor Environments Professional Practice Networks’ leadership teams. Today, we share dispatches from the Planting Design PPN team:
Mark Dennis, ASLA
Senior Landscape Architect, Knot Design
Washington, D.C.
Like all work-at-home, school-at-home, everything-at-home families these days, our own needs for outdoor connections are more persistent and unyielding than ever. We are here in Capitol Hill just a few doors down from Lincoln Park, a key element of the L’Enfant plan and among the oldest parks in Washington. The surging activity at Lincoln Park during the pandemic provides proof of just how crucial even the most fundamental aspects of amenity planning are in our society, while simultaneously highlighting the profound, persistent lack of funding for preservation and maintenance.
by David Hopman, ASLA, PLA
One of the best parts of my morning routine is to take a brisk-paced walk with my wife through our leafy suburban neighborhood in Arlington, Texas. It is a great chance to catch up on events, enjoy the changeable weather patterns in North Texas, greet and (occasionally) get caught up with our neighbors, enjoy the mature vegetation, and get the blood moving before a busy day. The neighborhood has very low non-arterial traffic flow that allows people and cars to comfortably coexist on the asphalt streets that are without sidewalks. However, at several points along our route, it invariably happens—the rise of the machines! Our morning reverie is interrupted with deafening sounds and billows of pollution and dust from gasoline-powered lawn and garden equipment (GPLGE).
These “machines in the garden” are ever with us, as was recently confirmed by a visit to Bloedel Reserve on Bainbridge Island near Seattle. Bloedel is one of my favorite places to return to and I always take the opportunity when I am in Seattle. Unfortunately, my aesthetic reverie at Bloedel was impacted by power equipment during my visit this summer and then became one of the incitements for this post.
As landscape architects, we are often responsible for designing the landscapes that are maintained by these environmentally and aesthetically abusive machines. Many people have written over the years about lower-maintenance alternatives to lawns and hedges, but adoption has been painfully slow. There is also surprisingly little emphasis on the effects of GPLGE on environmental quality by ASLA and by regulators. In Texas, the primary regulator for emissions is The Texas Commission on Environmental Quality (TCEQ). Their website has many suggestions for improving air and water quality. Drilling down to Voluntary Tips for Citizens and Businesses to improve air quality will eventually lead to a webpage devoted to lawn and garden care. On this page there are tips for harvesting and saving water, organic gardening, native plants, using trees to save energy, using less pesticides and herbicides, etc. GPLGE is very conspicuously absent.
by Mark Dennis, ASLA, PLA, AICP
An Interview with Austin Eischeid, Planting Designer
Describe your background a bit, and how you came to do planting design?
I started out experimenting in the vegetable garden as a kid. My parents wanted to show my sister and I where our veggies came from and I took a liking to it. I began experimenting with roses and found out how much work they were. I wasn’t willing to put in the time for dead-heading, watering through droughts, and treating them chemically. I was amazed to see entire sedum plants grow from a couple of cut stems, but I grew tired of them very quickly as my garden became overrun by sedum! I began experimenting with adding more annuals, perennials, and grasses, and the learning never ended. It was the only thing I could imagine going to college for, and it seemed I was destined to go to Iowa State University for a BS in Horticulture with an emphasis on landscape design.
While at Iowa State I heard Roy Diblik speak on perennials. His plantings were so vivid and inspiring, like nothing I’d ever seen before, and this was when I knew I had to become a planting designer. He spoke about his ‘Know Maintenance‘ approach to design, how there would always be some degree of maintenance, but that you had to really know your plants to build a sustainable plant community. Roy then became my mentor and introduced me to strong, hardy, long-lived perennials. For Roy, using perennials was about much more than just the flower; it was about overall texture and form for visual interest, winter structure, seasonality, and whether it behaved itself or not (for example, spreading or over-seeding).
by Michele Richmond, PLA, ASLA, SITES® AP, LEED® Green Associate
Can you plant a site with species that cause little to no allergies in patients? That was the specific request from our client for a site comprised of a community healthcare clinic and workforce and affordable housing. Many of our client’s patients are traumatized children with asthma and allergies. The goal of the building and landscape design was to create a safe place allowing for positive experiences for children coming to the clinic. In this context, a single allergy attack removes children from this safe space and can set back their recovery. So, what to plant?
Allergies and Asthma in America
Today, more than 50 million people in the US have allergies and asthma [i], including hay fever and respiratory, food, and skin allergies that can come from plants in our landscape. Allergies can be a onetime event or a constant reaction to pollen. Currently, allergies are the sixth leading cause of chronic illness in the US, resulting in 200,000 emergency visits a year [ii] and costing more than $18 billion annually [iii]. In Washington State, asthma is the most common chronic illness for low-income children. Asthma cases have doubled in the population at large and quadrupled among low income families in the last thirty years [iv].
While allergies largely cannot be prevented, we can lessen allergic reactions. As children, we learn to identify poison ivy and oak to avoid contact. As adults, we learn to check pollen counts [v] daily to determine if we need to take allergy medicine. We learn to identify and keep a healthy distance from plants that are the worst offenders to offset symptoms.
by Michael Keenan, ASLA
While plants are a primary color in the landscape architect’s palette, we often fail to grasp the complex challenges, laborious processes, and good luck it requires to bring healthy nursery stock to the market and ultimately to our projects. At the 2018 ASLA Annual Meeting and EXPO in Philly, the Planting Design Professional Practice Network (PPN) met to discuss the ever-important relationship between the landscape architect and the nursery grower. We heard from four nursery professionals to learn about the realities of nursery production, incoming production shortages, and how to foster a better relationship with your grower.
We were joined by:
Nancy led off with an insightful presentation of the tree growing process. We all know that trees are an investment in time, but we may not fully appreciate the dedicated efforts that go into growing the trees we specify.
As Nancy says, “Growing trees is an exercise in patience and faith in the future. It takes a long time and many skilled hands to grow beautiful, resilient, durable trees that will cast shade for future generations. Bringing new and improved trees to the marketplace is a collaborative, multi-generational effort that takes even longer.”
by David Hopman, ASLA, PLA
On August 12, 2018, I attended a meeting of a new committee created by the Environmental Water Research Institute (EWRI) of the American Society of Civil Engineers (ASCE). The task force, comprised of approximately 40 stormwater professionals, is titled: ASLA/EWRI Committee on Plants and Soils Performance in Green Stormwater Infrastructure (GSI). The committee will produce recommendations over the next few years that will be distributed in a booklet and online. This work will be specifically focused on providing better research-based guidelines for soil performance and plant performance as an overlapping, interrelated system rather than as individualized elements. The committee’s goal is to provide guidance on short-term, medium-, and long-term practices to ensure that systems maximize performance.
Additionally, other sub areas such as biodiversity, maintenance, and soil microbial functions will be considered. The landscape architects on the taskforce will take the lead in addressing aesthetics and other social parameters that can support or impede acceptance of Green Infrastructure as an important component of place making.
The first phase of the task force’s efforts is to create an annotated bibliography as an indicator of where research is headed and to reveal significant gaps that should be addressed. The literature review phase is being organized by Harris Trobman, Project Specialist in Green Infrastructure at the Center for Sustainable Development and Resilience, The University of District of Columbia. The committee needs good research-based literature, especially as it relates to the performance of plants in green infrastructure. If you have a favorite book or article that you would like to share, please send it to me by December 1, 2018, and I will format it for inclusion in the bibliography. Currently, the bibliography is reflective of the vast preponderance of research that has traditionally come from engineers and scientists. Please free to contact me with questions and/or comments as well. If you would like to format the citation yourself, I can send an example.
Jim Urban’s recorded presentation “Urban Street Tree Planting: Correcting Myths and Misconceptions” is now available through ASLA’s Online Learning series. Hosted by the Planting Design Professional Practice Network, this presentation provides valuable information on best practice recommendations for urban street tree design.
Despite 35 years of research, books, articles and lectures, the profession still maintains many myths and misconceptions about designing with trees in urban spaces. Tree health is still at risk from all too common and obsolete design errors. This webinar will point out the most common of these errors, and provide best practice recommendations to develop truly sustainable urban landscapes. Based on the six most critical concepts of designing for healthy trees, this session will teach sound, science based designs, details, and specifications. Better informed designers will have the tools to incorporate science and sustainability principles into the aesthetic principles that guide the design of these important landscape spaces.
Learning objectives:
• Understand best practices related to urban street tree planting.
• Incorporate the six most critical principles to attain sustainability in urban tree design.
• Use the latest research findings to make decisions on soil options for urban trees.
Speaker
James Urban, FASLA, ISA
Urban Trees + Soils
Planting Design at the ASLA Annual Meeting and EXPO in New Orleans, October 21-24, 2016
Planting Design Professional Practice Network (PPN) Meeting
Saturday, October 22, 12:45-1:30 PM
Jackson Square Meeting Room, PPN Live on the EXPO floor
At the Planting Design PPN meeting Saturday afternoon during the ASLA Annual Meeting and EXPO, we will discuss our PPN’s goals for the upcoming year, meet the members who have been shaping blog posts for The Field and plans for Online Learning webinars, and have an opportunity to sign up and volunteer to join the Planting Design leadership team. The short 45-minute meeting will also give us some time for a discussion about designing for intermingled plant combinations led by David Hopman, landscape architect, associate professor, and chair of the PPN, and Nigel Dunnett, Professor of Planting Design, University of Sheffield, UK. This is intended as a participatory event so bring your toughest concerns and best ideas to share about this important and emerging trend in planting design.
In addition to the Planting Design PPN meeting, there will also be a planting design-focused EXPO tour on Saturday, and the EXPO Reception featuring the PPNs on Sunday, 4:30-6:00 PM.
Planting Design PPN EXPO Tour (1.0 PDH LA CES/non-HSW)
Saturday, October 22, 9:45-10:45 AM
Tours will start from PPN Live on the EXPO floor
The Professional Practice Network (PPN) EXPO Tours at the Annual Meeting highlight new and improved products and how these improvements and services can assist in creating a successful design project. This tour of the EXPO floor will include the exhibitors: J. Frank Schmidt & Son Co., Bold Spring Nursery, The Plantium, and Star Roses and Plants. Sign up online to attend the PPN EXPO Tour!
Below, we highlight sessions with an emphasis on planting design.
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.
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.
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.
In 1998 Leslie Sauer Jones wrote The Once and Future Forest: A Guide to Forest Restoration Strategies. Embedded within the book’s forward, landscape architect Ian McHarg implored: “We must participate, with action and all the experience we can bring” in order to attempt to reverse environmental degradation and we can no longer expect our actions to be reversed with inaction. He further suggested that we embrace, “important havens, such as the interstices of cities” as critical canvasses for habitat enhancement and expansion for our native plants and animals.
Within our cities, large, contiguous tracts of vegetation, such as urban forests and riverfront corridors, offer critical ecological value potential. However, in more densely developed fragments of the city, where landscape design increasingly occurs, researchers are discovering that purposely selected woody plants can similarly provide animal species with viable urban habitat. Conceptualizing the ecological value of these urban interstices may be a function of perspective, or scale.
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.
Soil structure (how soil particles are held together to form larger structures within the soil) is recognized as an important property of a healthy soil. Grading, tilling, soil compaction and screening soils during the soil processing and mixing process damages structure. Structure makes significant contributions to improving root, air and water movement thru the soil. Soil screening is extremely damaging to structure but is included in most soil specifications.
Why do we screen soils and what happens if we do not? Prior to the mid 1970’s soils were rarely screened and landscape plants performed quite well. Installed soil was moved with clumps or peds throughout the stockpile. In the last 15-20 years farmers who have stopped tilling their soil have found significant improvements in soil performance. Several new research projects suggest that elimination of the screening and tilling processes in favor of mixing techniques or soil fracturing that preserve clumps of residual soil structure may improve landscape soils.
Data, data, data.
We know that all good science is based on adequate data. And if you’re reading this page, you probably also already know there is a lack of adequate data when it comes to the real-world performance of urban tree planting soils. This post is your chance to change that and add your own information to a shared database of soil performance data.
A bit of background: In 2014 we (Eric Kramer, ASLA, and Stephanie Hsia of ReedHilderbrand; Robert Uhlig, ASLA, of Halvorson Design; Bryant Scharenbroch, PhD of University of Wisconsin – Stevens Point; and Kelby Fite, PhD of Bartlett Research Labs) undertook a micro-study of seven sites in Boston — constructed urban landscape projects anywhere from 5 to 45 years old. Each project took a pro-active approach to designed soil systems, using suspended pavements, Cornell University structural soils, or sand-based soils. We took soil cores, recorded soils horizons, took lab samples and compared findings to what we knew about what had been installed. We also assessed the performance of the trees over time.
Stem girdling roots, kinked roots, J roots, T roots, and root collars buried deeply in the root package are one of the principle reasons whey trees and large shrubs fail to recover from transplanting or decline and even die at a young age after planting. These problems are typically created in the nursery by practices that do not produce plants with radial root architecture and place the root collar close to the surface of the soil. As a plant moves thru the production process from propagation to delivery at the site, there are many opportunities for root problems to develop in the plant.
Most plants are started in small containers and then gradually moved into larger containers. If the plant is sold in a container there may be three or four different container sizes. Each of these containers may result in a series of roots circling around the edges of the pot forming circling roots. Any of the circling roots above the root color can eventually choke the tree. Other roots may be deflected from the bottom of the container and grow upward to the surface forming a sharp kink in a root that may eventually become an important structural root. If these misshapen roots are not pruned at each shift in pot size they form an imprint of constricting roots in the next container. As trees are repotted they are also often placed too deeply in the next pot. Trees lined in the field may also be buried in the soil. This places the roots too deep in the soil where oxygen is less available at a critical point in the trees development.
When high-intensity rainfall events roll through cities, particularly those with combined sewer systems, peak flows increasingly overwhelm grey infrastructure, compromise water quality, and induce sedimentation and erosion. New research suggests that engineered soil and purposely selected plants within green infrastructure may help offset these flows by offering more benefit than most stormwater engineering models and municipalities acknowledge.
A handful of progressive entities – like the Chesapeake Stormwater Network and the Commonwealth of Virginia – now award extra stormwater credit for management approaches that deploy high-performance engineered soils, dense and varied planting palettes, or an inter-connected series of green infrastructure elements. More research is needed, however, to mobilize engineers, designers, and policy makers to rely more heavily on the “green” in green infrastructure.
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.
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:
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.
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.
Part 3: The National Green Industry ‘Utility’ Plant Palette
The next step forward in moving towards a better balance of aesthetics, environment, and ecology has flourished since the latter part of the 20th century with the introduction of better adapted plants by the national horticulture industry. These are the ‘workhorses’ used by landscape architects to cover large areas of ground in landscape development and to provide the structure and spatial definition desired for landscape designs. They are hybridized species of turf, groundcovers, annuals, perennials, shrubs, and trees that are rarely indigenous to the areas where they are planted. The massive scale of the areas in the United States covered by these plants makes them the primary target for the aesthetically qualified native polycultures that are the subject of this series. Turfgrasses alone cover over 63,000 square miles—about the size of the State of Florida—and may be the largest irrigated crop in the United States. [1]
As in part 2 of this series on fine gardening, the priorities of the companies and the plant palettes they produce are revealed by examining the search functions on their websites. These websites show what the companies want their customers to look for and, significantly, what is missing from the thinking that is reflected in the plant palettes produced.