It was in 1994 that PGAdesign, a landscape architecture firm in Oakland, California, requested a meeting with Oakland’s key city staffers and a consulting arborist to discuss recommendations that the company had been hired to prepare. What was the focus of all this attention? The care and preservation of a single tree: the “Jack London Oak.”
Carrying several layers of meaning for our city, this extraordinary specimen, a Coast Live Oak (Quercus agrifolia), was planted by the widow of the man who gave us The Call of the Wild and The Sea Wolf. London spent much of his childhood on the Oakland waterfront, and later became an oyster pirate as well as a member of the California Fish Patrol. By then, he had discovered the Oakland Public Library, where he started down the literary path to becoming the best-selling, highest paid, and most popular author of his time. His second wife, Charmian London—often referred to as his soul mate—planted the Jack London Oak in 1917, one year after her husband’s death.
More than 90 years later, this majestic tree anchors Oakland’s renewed civic center plaza. It grows in front of city hall and at the end of San Pablo Avenue, one of the East Bay’s longest and most historic streets. The Mayor’s inaugural address and other special events take place here. There are daily lunch crowds, noontime concerts and weekly craft fairs on the plaza.
The Coast Live Oak is native to California, and still thrives in the Oakland hills and environs. The species once grew along the streets of what is now a very urban downtown. The trees gave the city its name, and the Jack London Oak is now the key feature of the city’s logo, and an iconic symbol of our city and its history.
It is no surprise, then, that the tree received special attention after the powerful 1989 Loma Prieta earthquake that collapsed sections of major freeways as well as the Oakland Bay Bridge. Hundreds of buildings were damaged in the Bay Area, including Oakland’s classic city hall, the city administration building, and several others in the civic center. Some were repaired, including City Hall, and some were demolished, all of which required a comprehensive redesign of the civic center area. That also meant the expansion and redesign of the plaza that connects the component buildings.
|Image courtesy Chris Pattillo.
At the center of that open space was the Jack London Oak, and it became the focal point of the redesign. The importance of that tree—and others within the plaza—drew the attention of community activists, city staff, the city manager, and ultimately the mayor and city council who had to approve the redesign plan.
PGAdesign collaborated on the redesign with a team led by architect Y.H. Lee. We were charged with developing the approach, details and specifications for protecting the city’s namesake tree and ensuring its long-term health. These guidelines would define treatments to be implemented before, during, and after construction. All aspects of the tree’s care were examined, after which alternative treatments were outlined and analyzed.
Once the design approaches were developed, PGA caucused with key stakeholders, including representatives from the city’s parks, tree and maintenance departments, as well as our consulting arborist, Barrie Coate, and the city’s arborist, Dr. Bob Raabe. Given the importance of this heritage tree, PGA welcomed and promoted the highest level of scrutiny, input and debate. We laid out the issues using exhibits developed to illustrate each condition, then offered several recommendations as well as the rationale for each one. The meeting was then turned over to the attendees to question and critique every suggestion. Discussion continued until we reached a consensus.
PGA incorporated these resolutions into specifications and invited participants to review the contract documents. One objective of this elaborate process was to demonstrate how critical these decisions were. Another was to gain a commitment from city staff to monitor the work of the contractor throughout the year-long construction period.
Mr. Coate, PGA’s consulting arborist, evaluated the structural integrity of the tree and found: “The interior of the tree had been thinned excessively in the past. . . . there is inadequate foliage in the interior of the canopy.” This inhibits an increase in the diameter of the main limbs and branches. The arborist’s report explained, “The result of the loss of foliage feeding the individual limbs in areas other than branch ends has been production of extremely long limbs with all of their weight at the ends, poor branch and limb taper.” Indeed, a major branch failed in July of 1995 because of the poor branching structure and excessive end weight. It broke a second branch as it fell, creating a disfiguring hole in the regular canopy of the tree.
End-weight thinning to reduce the load, preceded by sub-surface fertilizing the winter before, was recommended to correct these structural problems. No major limb losses have occurred since then.
Image courtesy Chris Pattillo.
The lawn area surrounding the Jack London Oak has nearly doubled in size as part of the redesign, which also caused a discussion about raising the grade beyond the drip line. Raising the grade should normally be avoided to protect the health of a tree, but testing showed that the soil surrounding the oak was so compacted that it precluded penetration by roots. The added volume of friable soil provided by raising the grade provided an area for expanded root growth.
According to Mr. Coate, “Since the best way to increase vigor and overall condition of a tree is to encourage it to produce more absorbing root tips, which in turn increase the tree’s vascular activity and ultimately its ability to store carbohydrates in the trunk and roots, this fill soil will create an environment which would be conducive to production of new absorbing roots and should offer a significant benefit to the health of the tree.” PGA not only specified the type of soil but ensured that it not be compacted more than 80 percent. The specifications further directed how the soil would be placed, to avoid additional compaction in this zone. No changes to grade were made within the dripline.
The firm also provided detailed instructions for the demolition of a concrete vault and abandoned conduit within the canopy of the tree. These emphasized the importance of minimizing disturbance of the root system. As a result, conduits were cut off at grade and left in situ.
A subsurface irrigation system was proposed to irrigate the expanded lawn that would provide water four inches beneath the surface. This design offered a double benefit of avoiding overspray in a highly public space while conserving water as compared to a traditional overhead spray system. Circuiting considered the variation in exposure on different sides of the tree and plaza.
PGA provided detailed instructions to the contractor for protecting the oak before and during construction. A special training session was required to explain the purpose of the protective measures to the construction workers. Two fencing diagrams were provided that would be adjusted as needed to provide access at various stages of the plaza construction. Activity within the fenced area was strictly monitored and controlled. A thick layer of bark mulch was placed over the entire area beneath the canopy, which in turn was covered by plywood sheets to further protect the soil from compaction.
Much of this work was completed as part of a special purchase order that preceded execution of the plaza construction contract. This enabled the city to implement the pre-construction tasks—preparing the Jack London Oak for the construction phase and implementing protective measures—before any major work began.
While the responsibility for our city’s most visible icon was a bit unnerving, the success of our meticulous and thorough efforts has been very rewarding. The Jack London Oak is only a few blocks from our office, and whenever I walk past this extraordinary tree I appreciate its grandeur and obvious good health. The oak’s vigor has noticeably improved since the completion of the plaza, and new growth has filled the void in the canopy left by the limb that broke during the design phase.
Others may take all of this for granted, but I welcome each new, healthy leaf.
Chris Pattillo, ASLA, is a principal at PGAdesign Inc. and can be reached at: firstname.lastname@example.org.