Arborist and urban forest educator Ryan Senechal offers an analysis of the Technical Memorandum recently shared by the City of Victoria regarding its stated need to cut down Centennial Square’s giant sequoia tree. He says the tree is healthy, and could be pruned to achieve more openness, while keeping its cooling shade and other important eco-services.
by Ryan Senechal, MUFL, arborist and urban forest educator
1. The city of Victoria made specific and repeated note of an underground BC Hydro powerline which is encased in concrete and runs under the Sequoia’s root system. Councillor Caradonna and senior Parks staff have repeatedly expressed safety concerns about BC Hydro’s infrastructure, yet no specific information outlines a potential conflict investigated by Dialog or Talmack. No conflict with BC Hydro infrastructure was identified in either Dialog’s report or Talmack’s report.
2. The city has yet to acknowledge the important services the sequoia provides to the community, or show up for its own asset which (unlike the 60-year-old services underground), is not at the end of its service life. The Sequoia tree has many years of service left to provide to the city, and is itself important city infrastructure.
Dialog identifies aging infrastructure as a concern for continued root system conflict. However, underground services can be modernized, lined, relocated, or installed, using arboricultural management techniques — these are practices being conducted every day in our region, in order to retain trees through construction.
3. The incomplete removal of Cormorant Street road surface has been mentioned as a problem, with comments that it “restricts soil aeration and drainage impacting root growth and tree vitality”. This appears to be pure speculation. No evidence was provided to illustrate this relationship. The tree is healthy.
Those same buried road surface conditions were present when the tree was installed, and there is no indication that those subsurface conditions have changed dramatically, or potentially created an issue for the tree’s root system.
4. There is more than enough information here to suggest adequate work has not been conducted to investigate the tree’s potential to be retained in the redesign. Statements have been made by Dialog, city of Victoria senior Parks staff, and city councillors that lack evidence of thorough investigation onsite, relying on speculative comments produced – not from breaking ground and verifying – but from looking at maps, and other surface-level professional opinions.
5. Dialog commented on the ecosystem services to be provided by the planned 17 deciduous replacement trees, but no perspective was provided on those currently delivered by the Sequoia. A deciduous tree that is small at maturity has low potential to deliver equivalent benefits to the Sequoia, even when groups of them are planted. The benefits Dialog mentions are many years away. Dialog also commented on stormwater management delivery through the soil cells provided for the new trees, yet they have not conducted analysis of the current stormwater benefits offered by the existing lawn and Sequoia tree.
Along with their leaves, deciduous trees lose most of their potential to disrupt rainwater just as rainfall arrives each fall. We are reliant entirely on the soil volume’s ability to capture and slow rainwater from reaching storm drains. The Sequoia, on the other hand, provides year-round leaf area that slows rainwater before it is absorbed into a massive soil area.
Below is a summary of the Sequoia’s current ecoservices, calculated using iTree app:
- Leaf area: 2500 square metres
- Carbon storage: 7.5 tonnes
- Carbon sequestration (annually): 8.128 kg
- Avoided water runoff (annually): 4.162 cubic metres
- Water intercepted (annually): 21.43 cubic metres
- Potential Evapotranspiration (annually): 59.05 cubic metres
- Oxygen production (annually): 21.67 kg
- Input measurements: 168.7 cm diameter at 1.4m height, 22 m total height, 2 m crown base height, 15.2 m crown width (N/S), 14.5 crown width (E/W), 5 side crown light exposure, 1 to 5% crown missing, 1 to 5% crown dieback
6. Dialog appears to have a different view on the Sequoia’s health condition than the professional arborist who authored the construction impact assessment (Talmack Urban Forestry). The author of that report lists their name and certifications, which indicate their specialization as a professional arborist, consistent with the city of Victoria’s policies and expectations for comment on tree condition and tree risk assessment.
Such qualifications, for example, include ‘International Society of Arboriculture Certified Arborist’, and ‘Tree Risk Assessment Qualified’. The attending arborist who visited the site in March of 2024 determined the Sequoia to be in good health and good structural condition. They recommended the tree be removed because of the design constraints that were provided to them (presumably by Dialog) in the form of plans for the square, and there are no indications that infrastructure conflicts or tree health or tree stability were the rationale for the removal recommendation.
City of Victoria previously shared condition information on its open data portal, as gathered by city of Victoria Parks arborists and contractors. The condition ratings that were last publicly available (before the City quietly removed condition information from the public tree species data layer in 2021) were that the Sequoia was in good health and good structural condition as of June 17th, 2019.
7. Dialog notes the tree is shade-intolerant and therefore intolerant of urban growing conditions. This is counterfactual to the evidence we see with our own eyes, and contrary to what the academic literature says. Sequoias exist in abundance in Victoria in a wide range of growing conditions, including soil conditions and light availability. Think about the Sequoia at Honda City. Think about the Sequoia(s) at the Victoria Art Gallery. There are two Sequoias growing in the shade of a high-rise building, surrounded by other trees at the intersection of Fisgard and Quadra. The report author has had little exposure to the urban forest in Victoria if their opinions on Sequoia species’ viability in downtown Victoria is any indication.
8. Centennial Square’s Sequoia has about the best sun exposure you could hope for in the downtown realm, and that light availability is not going to change, based on the designs the city has shared.
9. The report author notes “most horticulturalists and arborists recommend that giant Sequoia should only be planted in areas with abundant space”. It’s not ethical for me to speak on behalf of “most horticulturalists and arborists” without their consent, but my professional opinion is that this Sequoia’s existing soil area and above ground growing space is abundant and appropriate for the species. We’re not talking about whether or not it is appropriate to plant a tree, we’re talking about a tree that already exists.
10. The report author references an established critical root zone radius of 19.8m, and suggests that it has already outgrown its root space. The report author would be wise to refer to Industry Best Management Practices produced by the International Society of Arboriculture guiding tree management through construction, which provides important context overtop what we imagine as a radius of root system around the tree. Critical root zones are areas defined where any work ingress requires arboricultural management techniques.
This is the area often visually identified by orange fencing wrapped around trees’ root systems during construction. That area is not necessarily off limits. Instead, it requires knowledgeable and qualified professionals to guide or make recommendations that will minimize stress to the tree. When critical root zones need to be accessed on private property, including for modifying parts of the tree’s root system to allow for utility repairs or new installations, these conditions are authorized by arborist staff at the city of Victoria.
The author of the Technical report has ignored the consulting arborists’ role in providing technical solutions where a desired critical root zone cannot be achieved. This is substandard practice in the design and building of urban realm renewal.
11. The Memorandum lists no author and no staff qualifications specific to arboricultural expertise.
12. The Design firm lists no professional arborists or urban foresters on their staff profile page.
13. The references provided to support Dialog’s opinions on Sequoia amount to two horticultural hobbyist blogs, and information provided by the city. Horticulture blogs aimed at a consumer audience are not traditional forms of professional evidence, and are not contextual to urban arboriculture.