Have you encountered an exceptionally large tree while hiking in the Forest Preserves? If so, we invite you to nominate it as a champion tree. A champion tree is recognized as the largest or most significant specimen of its species, whether native or non-native, celebrating the diversity of our natural environment and emphasizing the vital role these trees play in local ecosystems.

To measure a tree’s size, please use the following formula:

Circumference (inches) + Total Height (feet) + ¼ Average Crown Width (feet) = Total Score.

Once a tree is nominated, a Forest Preserves tree inspector will verify its species and dimensions. If the tree qualifies, it will be officially added to the Champion Tree Register and included on our interactive Champion Tree Map. Nominators of certified champion trees will receive a certificate of recognition and be acknowledged in the official record.

If a champion tree is an Illinois native and exceptionally large, it may also be eligible for Illinois’ Big Tree Register. In such cases, the Forest Preserves will submit the nomination for state-level consideration.

Nomination Requirements

Nominations for the Champion Tree Register of the Forest Preserve District of Cook County must:

• be a tree, not a shrub
• be located on a Forest Preserve District of Cook County holding
• include all required information on nomination form

Tread Lightly on the Land

Nominators are expected to exercise discretion in surveying a tree. Stay on trails wherever possible, and avoid trampling sensitive habitat surrounding any tree. If you believe you have a record in a sensitive area, contact a District ecologist before making measurements. Record-holding trees in sensitive areas may not be displayed on public lists to prevent trampling and soil compaction by big-tree tourists.

How to Measure a Tree

All nominations must include measurements or estimates for:

• Circumference (inches)
• Vertical Height (feet)
• Average Crown Spread (feet)

How to Find the Circumference*

Circumference is measured at 4.5 feet above ground level. Unfortunately, for measuring purposes, not all trees have a single, straight, branch-free main stem. Therefore, in order to properly measure tree circumference, it must be determined whether the tree has a single stem that can be measured at 4.5 feet; a single stem with a growth, defect, or fork directly at 4.5 feet; or two or more stems growing very close to one another.

If the tree has a growth, defect, or forks directly at 4.5 feet, simply measure the smallest circumference below 4.5 feet. If the tree is growing on a slope, take the circumference measurement at 4.5 feet above the midpoint of the base of the tree.

Stems that have clear separation at or “near” the ground should be considered separate trees and measured accordingly. Likewise, if the circumference measurement below the lowest fork places the measurement at ground level, then it should also be considered separate trees. Please note, it is up to the nominator and the inspector to determine if the tree is, and always was, one tree or if it is actually the result of two or more stems that began as separate sprouts and fused together. Quite often on multi-stemmed trees, there is a “seam” indicated where the two stems fused together (adapted from National Register of Big Trees). Useful tools to measure circumference include a forester’s diameter tape or any flexible tape-measuring device.

If you do not have a tape measure long enough, a long string that you can mark and measure later with a ruler will work.

How to Estimate Total Height*

Vertical Height is the measurement of the vertical distance between the base of the tree and the topmost branch. Quite often, the topmost branch will not be directly over the base of the tree, so adjust accordingly. To improve accuracy, please take several height measurements and average the results. Useful tools for measuring tree height include stick method, telescoping pole, drop-line, transit, Abney level, clinometer, laser hypsometer, Haga altimeter, yardstick, etc.

How to Estimate Average Crown Spread*

Average Crown Spread is determined by taking the widest horizontal distance (spread) of the crown and averaging it with a crown spread measurement taken at right angles to the widest measurement. Useful tools for determining average crown spread include wooden stakes or wire flags and a 100-foot tape measure.

1. Observe and identify the widest crown spread, from crown edge to crown edge. Identify these two points with markers or wire flagging. Using a tape measure, record the horizontal distance between these two points (A to B).
2. Observe and identify the crown spread at right angles to the two measurement points identified in Step 1. Again, using a tape measure, record the horizontal distance between these two points (C to D).
3. Add the crown spread measurements from Step 1 and Step 2, and divide by two. This number is the
   average crown spread.

*Measurement instructions courtesy of University of Illinois Extension Forestry.