Plant It Right - New Details and Specifications for City Trees are Based in Science and Ready to be Used in Contract Documents

Landscape Architecture Magazine, December 2014 (with Tyson Carroll)

Excerpt: With the goal of developing science-based specifications and details, Brian Kempf and Tyson Carroll at the Urban Tree Foundation [...] collaborated with James Urban, FASLA [...], and Ed Gilman, a professor of urban trees and landscape plants at the University of Florida, Gainesville, to create a set of peer-reviewed documents in four areas of practice: planting, planting soil irrigation, and tree preservation. [...]

The importance of science-based specifications arises from challenges landscape architects must deal with in projects and on sites. In the past several decades, projects have become increasingly complicated, requiring a higher level of construction knowledge and coordination of disciplines. Design ideas increasingly push the limits of natural systems or, worse, ignore nature's limitations. Urban soils make it difficult to establish plants and preserve large trees. 

Read the full article here.
View/download the specifications and details here

Letter to the Editor - Response to "The Dirt on Soils"

Ground: Landscape Architecture Quarterly

Excerpt: I read with special interest and enjoyment the recent Round Table in Ground, "The Dirt on Soils" [Ground 25]. You have raised the bar on this topic for our profession. An excellent panel, and Jack Legg brought a refreshing dose of hard science to the discussion. I offer a couple of comments and additions.

First, not everyone agrees that the material into which we plant should “not be called dirt.” I, for one, do not agree, and I think it might help the discussion to reserve the word soil for use only when it meets the definition of an agricultural soil scientist – that being natural, undisturbed soil. 

Read the full letter here.

Soils: The Measure of Moisture

Landscape Architecture Magazine, January 2014

Excerpt: Most projects don’t have a soil scientist as a consultant, which leaves landscape architects to make important field decisions during construction. We need to specify soil moisture as part of the process of installing and compacting soils, and managing soil moisture is a critical part of plant establishment afterward. Working with wet soils can damage the performance of those soils, and allowing root balls to dry out can create tree stress problems that may affect tree growth far beyond the guarantee period.

Read the full article here or download it here.

The Root of the Problem

Landscape Architecture Magazine, April 2013

Excerpt: For now, only you can keep trees with ill-formed roots from leaving the nursery

In the mid-1990s, practitioners and researchers were noticing a disturbing trend. Trees were increasingly
declining as they reached maturity. The problem was not limited to one species but affected many nursery-grown trees. Gary Johnson, a scientist at the University of Minnesota Extension Service, looks at hundreds of dead or dying trees each year. He would inspect the trees’ leaves and bark for signs of disease or insect damage, but, at some point, he began to look at the bases of the trees as well. He saw many trees that were slowly strangling themselves with their own roots.

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Tied to be Fit

Landscape Architecture Magazine, January 2012

Excerpt: Staking newly planted trees doesn't always do them a favor. 

Many years ago, Henry Arnold, FASLA, described to me a row of trees near his office that all broke at the same time in a strong wind. He stopped to investigate the unusual occurrence and found the guy wires used to stake the tree embedded in the trunk of each tree at the point where they snapped off. It's a familiar sight - a tree planted three or four years ago, still staked in place. The ties meant to keep the tree growing straight have deformed it - maybe even strangled it. But despite the potential for catastrophic failure, most tree planting specifications automatically require contractors to stabilize newly planted trees.

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The Bare-Root Cause

Landscape Architecture Magazine, June 2011

Excerpt: Bare-root planting is a better choice for tree health. 

Tree planting may be the essence of sustainable architecture, but the methods of harvesting and installation are not always specified in the most sustainable ways. Each of the most common options for tree planting - balled and burlapped, tree-spade planting, and container-grown trees - has environmental costs that reduce or even eliminate the trees' contributions to the sustainability equation. Before World War II, bare-root planting was the common method to move trees both large and small. Projects did not typically move at a fast pace, and people were more patient to wait until the right time to plant. After the war, increasingly larger trees were specified to meet both designer and client needs for instant gratification, and projects began to move more rapidly, with plantings often required at almost all times of year. 

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Urban Soils - Part 1: Understanding Compaction

Excerpt from Up By Roots - published in the International Society of Arboriculture Magazine, April 2008

Abstract: The natural soil-forming process tends to create soil that is at suitable levels of compaction (or, to use the scientific term, bulk density) for ground stability and the growth of some kind of plants. Few natural places exist where the soil bulk density is so high that plants will not grow.

Human activity tends to change the compaction level in the soil, most often making it more compact, but sometimes reducing its compaction. Identifying compaction levels in the soil and when they need to be modified is a critical step in creating good growing conditions.

As soil becomes mechanically compacted, the organic bonds that were holding the soil structure are broken, and soil particles are pushed together, filling the pore space. Think of what would happen if you stepped on a bag of pop com. Your foot would crush the fluffy kernels together,and the spaces between them would be difficult to re-create.

The same goes for soil. As pore space is eliminated, space for air and water is lost, and roots must push harder to get through the soil. The plant has access to less water and grows fewer roots in the more difficult conditions.

Download the full article here.

Alternatives to Structural Soil for Urban Trees and Rain Water

Paper presented at Designing with Nature: The Art of Balance - American Society of Landscape Architects Annual Meeting, October 2007

Abstract: Compacted soils to support pavements and infrastructure increase the run off rate of rainwater. Only a small percentage of each rain event, even if the pavement is porous, can infiltrate compacted soil for aquifer regeneration and vegetation hydration. Soil compaction also stunts the growth of trees by restricting root penetration. Absorbing soils that are not compacted, placed under pavement can be a significant tool for rainwater management and improvement of the urban forest.

By using the BMP methods discussed below, paved city plazas, streetscapes, and town centers can become areas for rainwater mitigation. They can transform the urban forest into a rainwater mitigation asset. The strategies discussed will support roadways, parking lots and sidewalks while providing un-compacted soil volumes to absorb large amounts of water and enable large tree growth. These methods can contribute to sustainable designs in varying effectiveness for increases in water management with no loss of the paving's structural integrity. 

Using trees and their required soil for rainwater management has additional advantages over other rainwater management strategies. The large healthy tree canopies created by large volumes of absorbing soil provide other benefits. The tree's canopy cools the air and paving which helps reduce urban heat island impacts and cools run off water temperature. A large canopy absorbs the initial 1/10th of an inch of the rain event and evapo-transpires large amounts of water increasing the effectiveness of the system. Healthy, long-lived trees also contribute to the social and economic health of urban communities.

Download the full paper here.

Bringing Order to the Technical Dysfunction within the Urban Forest

Journal of Arboriculture, March 1992

Excerpt: In order to increase the success rate of trees planted in the urban environment, there must be a significant change in the way trees are planted. The wide diversity in soil conditions found within urban areas suggests that there should be modifications to planting details from one site to another. The profession of urban forestry and landscape architecture, however, continue to use the same planting details regardless of the quality of the existing soil. Further, no protocol exists to guide the decision making process to determine when to use different methodologies. This paper will present the framework for such a methodology and a series of possible changes to the way trees should be planted. The methodology is based on quantifiable levels of urbanization and soil quality, and proposes a logical approach to the design of planting details.

Download the full article here.

Evaluation of Tree Planting Practices in The Urban Landscape

Proceeding of the Fourth Urban Forestry Conference, October 1989

Excerpt: During the 1970s and 1980s the explosion of urban landscape architecture resulted in plazas and paved spaces punctuated by groves of trees. The growth and survival rates of these trees, however, was significantly lower than trees planted in more open situations. As streets were widened and new development was initiated at higher densities, utility requirements increased the demand for available sidewalk space above and below ground. Simultaneously, the technology of construction changed; heavier and more efficient machinery, capable of moving larger volumes of earth and making deeper cuts, resulted in soils at construction sites that were highly disturbed and compacted. To add insult to injury, there was also a significant erosion in environmental quality; beyond the obvious air pollution problems, trees were now required to withstand a variety of chemicals, including de-icing salts, cleaning fluids, and lawn chemicals. 

Download the full article here