Lincoln Park Zoo’s massive bur oak slated for removal

For the next few months, Katrina Quint has one request for visitors to the Lincoln Park Zoo: Look up.

Across from the white-cheeked gibbon enclosure sits a great, sprawling bur oak tree, about 45 feet tall. Because it is naturally dying, the tree is set to be removed this spring. There is no disease present, but this year, the tree only produced a few leaves and its top branches were “completely dead,” said Quint, who is the director of horticulture for the zoo.

The tree has potentially been at the site since around 1800, according to Quint’s estimates based on the tree’s trunk diameter, predating the incorporation of the city of Chicago. It’s the oldest of several great bur oak trees around which the zoo was built in 1868, Quint said.

The tree may be easy to miss, similar in height to those around it. But a closer look reveals the massive size of its trunk. “Two people can barely touch hands hugging around the base of the tree,” Quint said.

While many people may not notice the tree regularly, its absence will change the fabric of the landscape, Quint said.

Mary Ann Stott, 74, said she has been visiting the Lincoln Park Zoo since she was 9 months old and is “heartbroken” to see the tree go.

“That tree has just witnessed so much history, and so much change,” Stott said.

About 10 years ago, Lincoln Park Zoo moved from merely maintaining its landscape to working toward arboretum status and becoming a public garden, Quint said. In 2019, the zoo achieved arboretum status, an accreditation that recognizes the site as a place for the monitoring and preservation of woody plants.

Part of that switch meant prioritizing the zoo’s existing assets — such as the bur oaks responsible for much of its tree canopy.

In August 2020, the oldest tree dropped all of its leaves, significantly early and a signal to the zoo staff that something was wrong. In an effort to save it, they tried root invigoration, a process that involves pushing air into the ground and blowing out the soil near the root zone, using a tool that looks like a power washer. The process aims to relieve the compacting of the soil, which occurs when soil is trod on to the point where water and nutrients can’t reach the roots. This year, the tree produced few leaves.

“It is a natural end for this tree,” Quint said. “It is so old, it’s not going to last forever, unfortunately. I wish that weren’t the case.”

In addition to age, Quint also said she believes unpredictable fluctuations in weather over the past five years — overwatering from spring showers followed by periods of severe storms and drought over summer — are factors in the tree’s deterioration.

The large branches of a bur oak tree at Lincoln Park Zoo span over a portion of the zoo grounds on Nov. 22, 2022.

Quint, who started working at the zoo three years ago, said she’s been saving acorns dropped by the zoo’s trees. These acorns will be grown to bolster the tree canopy, part of the zoo’s long-term plan to protect the landscape in the future amid the worsening effects of climate change. Through the natural work of squirrels, the zoo already has about 15 young bur oaks, ranging in age from infancy to 15 years old, she said. IThe zoo has 40 bur oaks on its property, including six of its oldest trees

The zoo has saved six acorns produced by the bur oak slated for removal, Quint said, with many more that could have been dropped by the tree, but it’s hard to confirm. The zoo also hopes to save some cuttings to grow as well.

Parts of the tree have already been cut away due to a storm and for the safety of visitors passing by, leaving branches that end in clean cuts hanging just shy of the sidewalk between the white-cheeked gibbon habitat and the zoo’s lawn. The decision to completely remove the tree was difficult, Quint said.

“Once the tree is completely gone, people will notice, and I feel like they didn’t take the chance to really see how majestic of a tree it really was or take the time to appreciate it,” Quint said.

There is no doubt the bur oak at Lincoln Park Zoo is old, but just how old is up for debate.

Quint estimated it to be between 250 and 300 years old, a figure generated by measuring the diameter of the tree trunk and cross-referencing it with a chart from the Morton Arboretum.

However, Christy Rollinson, forest ecologist for the Morton Arboretum, said use of that chart is no longer recommended and that a tree’s size, especially for older, bigger trees, is not an effective predictor of age.

A closer view of a centuries-old bur oak tree at Lincoln Park Zoo.

For “the quintessential Midwestern oak species,” known for its big leaves and mossy acorns, being 250 or 300 years old is possible, Rollinson said. “But we’re starting to get into the oldest trees ever found of these kind of species.”

Rollinson said the only way to determine a tree’s age is through counting its rings from a cross section, taken by cutting the tree in half, or through a tree core, a pencil-sized piece of wood taken out of the tree. Quint said the zoo can take a core sample but hasn’t yet.

The oldest tree Rollinson said she has encountered at the Morton Arboretum was planted in 1772. These old, historical trees are rare, but scattered throughout the city, she said.

“The Lincoln Park Zoo does sit in an area that was historically wooded,” she said.

For the past 10 years, the screen saver on Stott’s phone has been a picture of a bur oak in the middle of a cornfield, taken on Randall Road in Batavia.

“The oak symbolizes for me strength and courage and resiliency,” she said.

Viridiana Arango and Ximena Segura, visiting from Texas, sat on a bench Monday underneath the bur oak to rest. They said they hadn’t noticed the tree during their visit but after reading a small golden plaque stationed in front of the tree, they each snapped a picture of the tree.

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“You don’t realize how old a tree is, but it’s really interesting,” Arango, 25, said. “It’s a part of history.”

Lincoln Park Zoo plans to carefully remove the bur oak tree from the zoo grounds next spring and encourages patrons to visit for a final look at this piece of natural history.

As a horticulturist and arborist, Kelly Cullison of Round Lake said she can’t help but notice the trees she comes across. She plans to visit the Lincoln Park Zoo in early December to see the tree.

“Saying goodbye, seeing the decline long term, personally is heartbreaking,” she said.

Cullison said she hopes the zoo will honor the history of the tree by preserving its cross section and putting it on display, pointing out the tree rings that correspond with major historical events, like women’s liberation or the year the iPhone came out.

Stott hopes to visit the bur oak one more time before the spring to “thank it for being such a wonderful tree.”

“I’ll miss that tree,” Stott said. “And I think if we treasured everything, like the trees, like the plants, like all the wildlife that lives here, it would be a completely different world. Sometimes we are just so busy rushing around, we don’t realize notice the beauty that’s right in front of us.”

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