Tag Archives: Philip van Wassenaer

Designing with Trees in Mind: Preserving trees or adding new ones

Root exploration using a hydro-vac (left) exposes roots before excavation with machinery. Careful root pruning (right) eliminates further root damage which would otherwise be caused by tearing, pulling, or fracturing of roots, reducing tree injury. Photo © Philip van Wassenaer


By Alex Satel, MFC, and Philip van Wassenaer, B.Sc., MFC

Trees are immensely valuable resources. This is especially true in urban areas, where residents benefit greatly from the ecological services trees provide. As such, they are worthy of the same level of consideration as any other components of site design.

Whether the issue is to preserve existing trees on the site or to incorporate new trees into site design, an arborist or urban forester should be involved at the front end of the design process and throughout the duration of site development, working in concert with site designers, engineers, planners, and construction personnel. One should keep in mind the wide range of factors affecting the trees on development sites will significantly contribute to the successful outcome of any site design.

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Designing with Trees in Mind: Incorporating new trees into site design

Optimal soil structure for tree growth. Image courtesy Urban Forest Innovations Inc.


By Alex Satel, MFC, and Philip van Wassenaer, B.Sc., MFC

Understanding tree requirements for growth and survival is critical to effectively integrate new trees into site design. These requirements must be provided by the tree’s habitat; otherwise, plantings on the site will not achieve their full genetic potential and, as they languish, will result in increased maintenance costs and an ultimately failed landscape and site design.

Three critical factors must be kept in mind when new trees are being incorporated into a site design: above-ground, below-ground, and tree-specific factors.

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Designing with Trees in Mind: Preserving existing trees

Effective tree protection is a key component of good design on sites with existing trees to be retained. Photo © Alex Satel


By Alex Satel, MFC, and Philip van Wassenaer, B.Sc., MFC

When it is an objective of site design and development, successful tree preservation is almost always achievable. However, it requires careful planning, implementation, and post-development follow-up. All too often, the process begins with a preliminary site design, which is then reviewed for potential impacts on existing trees. Although common, this is not the best approach.

The following steps, if undertaken in sequence, can maximize opportunities for tree protection on virtually any development site.
1. Create a tree inventory.
2. Identify trees suitable for preservation.
3. Assess potential impacts.
4. Modify site design.
5. Identify tree work required before removal or grading.
6. Prepare and implement tree protection measures.
7. Monitor trees during site works.
8. Prepare and implement a post-construction maintenance plan.

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Designing with Trees in Mind: Design challenges

Root loss through this type of construction leads to tree mortality or failure. Photo © Philip van Wassenaer


By Alex Satel, MFC, and Philip van Wassenaer, B.Sc., MFC

When contemplating site development, there are two main considerations with regard to trees: can existing trees be effectively preserved and contribute to the site, and what opportunities are there to successfully incorporate new ones into the design? There are challenges to both options, but with careful consideration, both can be accomplished.

There are many ways trees can be negatively affected by construction activities; some more obvious than others. The main impacts to trees due to construction include the following:
● root loss;
● root stress;
● direct wounding;
● inadequate soil moisture;
● excess soil moisture;
● air;
● light;
● water;
● nutrients;
● temperature;
● space; and
● soil.

Read the full article: Designing with Trees in Mind: Incorporating trees into site development

Designing with Trees in Mind: All about the roots

Tree roots are shallow and extensive. Image courtesy City of Toronto


By Alex Satel, MFC, and Philip van Wassenaer, B.Sc., MFC

For site designers (e.g. engineers and landscape architects) to successfully design with trees in mind, a basic understanding of tree roots is a must. A common and persistent understanding of the root system is it roughly mirrors the canopy with thick, deep-spreading roots that look like branches. This perception is far from the truth, however; most trees’ root systems are in fact fairly extensive and relatively shallow.

There are three key components of the tree-rooting system. Structural roots are located near the base of the trunk, and their primary function is to help stabilize the tree. Long and rope-like transport roots emerge from the structural system and connect feeder roots to the tree’s vascular system. The fine or feeder root system is an extensive network of very small roots that collect air, water, and nutrients from the soil. These are usually found in the top 300 mm (12 in.) of soil, and are visible in the thick root masses that can be dug up with a hand shovel. Feeder roots can be found well beyond the edge of the tree canopy (i.e. drip line); in some cases, extending more than three times its diameter.

All three components of the tree root system are susceptible to considerable damage if any type of site disturbance is undertaken in close proximity to a tree. On newly developed sites, opportunities for root development—critical to long-term tree health—can be significantly reduced through poor site design or failing to plan to accommodate the needs of trees.

Read the full article: Designing with Trees in Mind: Incorporating trees into site development