You may have seen that the 250- to 300-year old bur oak (Quercus macrocarpa) on Lincoln Park Zoo’s South Lawn is at the natural end of its life—the news has been featured in local news outlets, such as WTTW. As the articles about it point out, the tree predates not only the founding of Chicago, but the founding of the United States, and, as a safety measure, it will be removed it this spring. You still have some time to view this beautiful example of a legacy tree and come say goodbye.
In fact, saying goodbye will be difficult for staff members who have worked to take care of this tree and all the trees of interest at the zoo. “We were slightly joking the other day that the horticulture team might need the day off when the tree comes down because it’s very sad for us to see something so beautiful removed,” Director of Horticulture Katrina Quint told WTTW. “It’s a big deal for us.”
About Bur Oaks
But what, exactly, makes the bur oak tree such a remarkable and distinguished resident of the zoo? We already know that its age means it has seen a lot—if only it could talk!
Bur oaks are native to the central U.S. and the southern part of Canada. They are deciduous trees (they drop their leaves in the fall) that typically grow to 70 or 80 feet, but can get up to 150 feet tall or even more. Their trunks can be 4 to 5 feet in diameter at chest height. They belong to the family of white oaks, with grayish-brown bark that has irregular, cocky furrows. The crown of the tree (the leaf-bearing branches) usually spreads pretty widely, as you can see with the bur oak on the zoo’s South Lawn.
These trees like moist soil near rivers, but thrive in many different habitats, including prairies and savannas, because they are one of the most drought-resistant species of oak. Bur oaks grow very slowly, though, and don’t generally even bear seeds before they’re 35 years old—but they can continue bearing seeds for up to 400 years, which is longer than any other oak species in North America.
Tiny flowers bloom on bur oaks in the spring; male and female flowers grow on the same tree. Male flowers grow in long, drooping clusters called catkins, while female flowers grow singly or in small clusters. Pollination occurs by wind, and the acorns—which have a hair-like fringe—are larger than that of any oak in the U.S.
Bur oaks have a long taproot that lets them access deep groundwater, which helps them survive in drier conditions. And this ability to abide makes this species an amazing resource for wildlife. Insect larvae eat the leaves or bark. The insects, as well as the tree’s acorns, are consumed by birds. Bears, raccoons, deer, squirrels, and other animals also eat the acorns. The bur oak is actually named for the bristly quality of the fringe on the acorns.
And naturally, the tree provides living space and shelter for a whole slew of other creatures. Not only do birds build nests in bur oaks, but older trees contain cavities where squirrels and owls can stay out of the elements. The bur oak’s wide canopy spread also makes it a great place for larger animals and people to get some shade.
Bur oaks are valued by humans for other reasons. They offer a high-quality lumber that is water-resistant, which means it can be used outdoors; if you go to your local Home Depot and get white oak lumber, it’s likely from a bur oak. Bur oak wood is hard and durable, has good decay resistance, and is easy to work with—plus, it has a signature oaky odor that people like.
Additionally, bur oaks make attractive ornamental trees that can withstand harsh weather conditions (hello, Chicago). Thus, they are a good choice for creating windbreaks, which protect soil from erosion by wind. As sustainable trees native to this region, listed as of Least Concern by the IUCN, bur oaks are a great choice for landscaping.
The Historical and Cultural Significance of Bur Oaks
Bur oaks aren’t just valued for their utility in the modern day; they were used for many things from railroad ties to livestock forage in colonial America. Native Americans used bur oak as a food source and for medicinal purposes (for heart problems as well as other ailments) as well as for shade and protection for encampments. They likely used bur oak wood as fuel and to make tools as well.
In fact, there are numerous famous bur oaks around the country. In Kansas, one specific bur oak has historical significance because it was used as a Council Oak—under which U.S. officials met with Native American tribes (specifically, Osage and Kaw, or Kanza) in 1825 to sign a treaty giving Americans and Mexicans access to the Santa Fe Trail. The tree blew down in a windstorm in 1958 when it was 70 feet tall, but has since been replaced by a direct decedent grown from an acorn harvested from the original oak and planted in the town of Council Grove, Kansas. The town is a National Historic Landmark because of this event.
Not far from Columbia, Missouri, the McBaine Burr Oak Tree is said to be 350-400 years old and 90 feet tall with a 130-foot spread. It competes with another bur oak located in Paris, Kentucky, which was once measured at 96 feet tall with a 103-food spread, for biggest living bur oak.
Other famous and historic bur oak trees have existed in the U.S. as well. They include the President’s Oak, which used to stand on the campus of the University of Wisconsin, Madison but was taken down in 2015 as a result of decay resulting from aging issues and harsh climate conditions, much like the one here at Lincoln Park Zoo experienced. Another was the Council Oak in Sioux City, Iowa, which was rumored to be the site at which explorers Lewis and Clark met with local tribes; however, this information has never been verified. Ponca, Nebraska is home to the Old Oak Tree, said to be almost 400 years old.
The Death of a Bur Oak
In nature, dead trees don’t just represent the end of a life. Dead trees become an important part of ecosystems, supporting life and making it possible for other plants to grow. They allow more light to filter into new places through the canopy, encouraging germination. The nutrients stored in dead trees can be released back into the environment to sustain other life.
As for the bur oak here at Lincoln Park Zoo – it is in a popular area of the zoo and the large, heavy canopy branches reach over public pathways and pose a safety risk. The tree has already lost large branches in recent storms and the decision has been made to remove the tree completely.
Once removed, the tree will be reused, although staff hasn’t decided yet how to preserve and repurpose it in a way that respects its legacy. Although the tree’s remains won’t remain outside the way a tree in a wilder area would, this beautiful bur oak may end up supporting the zoo’s learning efforts or being utilized throughout animal habitats. So it, too, will become a continuing, valuable part of the zoo environment—just maybe not in the traditional way.
Other Bur Oaks at Lincoln Park Zoo
Although the bur oak that’s the oldest plant on zoo grounds will be gone as of spring, six additional bur oaks can currently be found on the South Lawn. They are all estimated to be more than 100 years old, and have naturally produced offspring that dot the surrounding landscape, including around Flamingo Pond. Eventually, these offshoots will replace their aging predecessors.
One of the most picturesque mature bur oak trees is south of the pond, viewable as you enter the zoo from Nature Boardwalk. Another stands just in front of the zoo’s West Gate along Stockton Avenue. Two more can be found on the north side of the zoo near Hurvis Family Learning Center. One is on the hillside adjacent to the building, and the other is across from the polar bear viewing area at Walter Family Arctic Tundra. This tree is especially interesting because it has five separate trunks. While such a state of affairs isn’t uncommon, it doesn’t represent a single tree’s growth—this phenomenon actually incorporates five trees that have grown together their entire lives.
You’ll also find bur oaks at Nature Boardwalk, including trees east and northeast of People’s Gas Pavilion. One that no longer lives was maintained and left partially standing in this area to support wildlife. Next time you’re at the zoo, see if you can locate these amazing trees yourself!