Illinois Extension is a resource available for all community members. We work hard to help residents find answers to burning questions, and solutions to challenges, and keep current on industry and university research. We provide education and outreach through a variety of outlets — this article is one of those methods. Another service provided by the Extension is the answering of individual calls or emails from community members. The type of questions we receive are as varied and unique as the trees in a forest. Some people call to inquire about pest and disease management. Others need assistance identifying a mysterious plant or planting recommendations. Occasionally, we get a call that is whimsical.
I received one of these calls the other day, which was a delight. The resident inquired where to find the largest cottonwood tree in the county. Unfortunately, not all questions have an easy answer, and as fun as this question was, it was also challenging. Champion tree records are not kept at the county level, so I was worried I would not be able to fully assist this caller.
As luck would have it, while on a tour of a Chippiannock Cemetery in Rock Island the following day, I observed a very large cottonwood tree. I noted it to our tour guide, who remarked that it was “one of, if not the largest in the county.” Armed with this information, I called the resident back. Through our conversation, I was able to share this information, but I also discovered why this inquiry was being made. The community member mentioned they were recently retired and now had time to seek out the large trees they love so much. Excited for this person and the search for large trees that lay ahead, I asked if they were familiar with the Illinois Big Tree Champions. They answered “no.”
As the website says, “the Illinois Big Tree Register (IBTR) was established in 1962 as a citizen outreach program to discover, record, recognize and appreciate the largest native tree species” in Illinois. Today, 116 species of Illinois trees are represented by a Big Tree Champion, and the hunt endures. This citizen science project continues, and anyone is welcome to get involved by becoming a volunteer big tree inspector or by nominating a tree.
Trees are evaluated, and the score is the sum of three measurements: tree circumference + height + ¼ average crown spread. Tree circumference (inches) is measured on the largest independent stem at approximately 4.5 feet above ground level. This measure is also known as “diameter at breast height,” or DBH.
Not all large trees have a single stem. To ensure consistency and fairness, instructions for measuring multi-stem trees or trees with fused trunks are provided in the nominating guide. Tree height is the distance between the top of the tree and the base of the tree. Height can be challenging to measure accurately. Tools and methods are available to help accurately measure tree height.
The average crown spread is calculated by measuring the crown’s widest distance plus the crown’s widest distance perpendicular to the first measurement, then dividing by two. The Illinois Big Tree Nominating Guide includes more detailed descriptions of how big trees are measured.
Beyond nominating a tree, visiting and appreciating these tree champions can be equally enjoyable. An interactive map is managed through the University of Illinois and is the “go-to” resource when planning a big tree-themed road trip.
Illinois’ big tree champions registry is part of a national registry of champion trees managed through the American Forests organization. As of today, this national registry keeps a record of 561 trees. The database can be filtered by genus, scientific name, common name or state. When Illinois is selected, two trees are listed as National Champions: Kansas hawthorn (Crataegus coccinioides) and Ohio buckeye (Aesculus glabra), both located in DuPage County.
For those interested in a midwestern tree tour, states neighboring Illinois also keep records of state champion trees, including Iowa, Wisconsin, Indiana, Kentucky and Missouri.
Whether traveling across the country or closer to home, finding champion trees along the route can add excitement and novelty to a trip. As the inquiring resident and I wrapped up our call, I wished them happy travels and thanked them for asking such a fun question. The last bit of information I had to share was the serendipitous species and location of the largest tree in Illinois … an eastern cottonwood growing in Byron Forest Preserve District in Ogle County.
Emily Swihart is a horticulture educator with UI Extension, serving Henry, Mercer, Rock Island and Stark counties. This column also appears in the “Good Growing” blog at go.illinois.edu/goodgrowing.