February 2, 2023

I can remember being impressed with some of the large trees in my neighborhood when I was quite young but it wasn’t until I was in perhaps 5th grade that I saw really big trees for the first time. After school, my friend John and I liked to go exploring along the Des Moines River, which was only a mile or so from our homes. Here we discovered cottonwoods, and some of them had trunks over five feet in diameter and they seemed incredibly tall. Gazing up at these giants for the first time was an exhilarating experience that truly inspired me. Over fifty years later, I still feel a sense of awe and wonder when I find an exceptionally large tree!

In the early days of my developing big tree interest, I had no mentor or even a direction to follow until 1972 when I discovered something very significant. While visiting the library, I came across an American Forestry Association magazine that had list of the national champion trees. As far as I was concerned that list was the most fascinating thing that had ever been printed. Around this time, I discovered a cottonwood from Hardin County that had a circumference of over 20’ and from that point on I was hooked on finding and measuring big trees! The American Forestry Association developed the “National Register of Big Trees” in 1940 but the Iowa Big Tree Program didn’t get started until 1978. After the Iowa Big Tree Program was implemented, I was no longer just finding and measuring big trees for myself, now I had a purpose that provided me with additional motivation to search for Iowa’s biggest trees!

Out of the 45 champions on the first listing of “Iowa’s Biggest Trees”, only a red cedar from Indianola remains as a champion today. The Big Tree Program changes as bigger trees are found and other champion trees are lost to storms, disease, old age and cutting. The record for the most champions for one species goes to the catalpa that has had ten different champions! Four of those former champs were lost, one was damaged, and the others were surpassed by larger specimens. Since 1978 over 1,200 trees, representing 153 species have been nominated to the Iowa Big Tree Program, but of those over 200 have been lost. Some champions become hazard trees and they have to be removed, but sometimes they are cut unnecessarily.

One purpose of the Big Tree Program is to reduce the unnecessary loss of Iowa’s big trees. Since so many of Iowa’s biggest trees stand on private property, it is important to identify these trees so the owners at least know what they have. If the owners of a champion tree or a tree close to champion size know their tree is significant, they are more likely to preserve the tree. For example, a champion American chestnut was cut because the owner didn’t like the spiny burs that cover the nuts. The owner told me if they had known the It was around this time tree was a champion, they would not have had the tree cut!

When one of my favorite big trees is lost, I take it hard; after all, I have had a connection to some of these friends for over forty years! You expect to lose a champion tree now and then to storms but the 2020 derecho was devastating. It destroyed countless trees, and several state record trees, including the champion swamp white oak, butternut, and ponderosa pine. Other champions were lost, and many were damaged. Despite the prospects of more severe storms, I’m still motivated to search for the largest trees, simply to answer this question. What are the maximum dimensions of Iowa’s trees?

Here are a few examples of what we have learned so far. Our largest tree is a cottonwood with a circumference of 29’9”, a height of 85’, and an average crown spread of 124’. This tree stands on private property in Franklin County. The second largest tree is a sycamore from Geode State Park. It has a circumference of 23’1”, a height of 107’, and an average crown spread of 82’. The third largest tree is a silver maple located on private property in Des Moines. It has a circumference of 22’8”, a height of 88’, and an average crown spread of 99’. The tallest tree in Iowa is a white pine from Fayette County that has a height of over 151’. Although these trees are large and tall, don’t forget there are many small tree species eligible to be nominated for the Big Tree Program. Some of the smaller trees include dogwoods, hawthorns, plums, American hornbeam, also called ironwood or musclewood, serviceberries and the prairie crabapple.

Why is it important to accurately measure the largest trees? Scientific publications and books including field guides may reference the dimensions of big trees based on the measurements included on state big tree listings. Unfortunately, a high percentage of trees were and still are, today being measured using the tangent method. This method typically overestimates tree heights, often by tens of feet! Besides inaccurate data in publications, trees with overstated dimensions prevent accurately measured trees from attaining the status of a champion.

To achieve a high degree of accuracy, the height of most of Iowa’s champion trees and contenders, has been measured using the sine plus sine technique. This method is the most accurate way to determine tree heights short of an actual tape drop! Although the best height measuring instruments are expensive, you don’t need top-of-the-line equipment to measure a tree for nomination. To learn how to measure a tree, see the Tree Measuring Guidelines section of this website.

Except for the loss of beloved champions and the rejection from the occasional owner who chooses not to cooperate, my participation in the Iowa Big Tree Program has been extremely rewarding. I enjoy all aspects of the big tree work. I enjoy the search which challenges my powers of observation and my identification skills. I’m a perfectionist and I find it very satisfying when I’m able to determine the precise measurements of a tree. Lastly, as an artist and a photographer, I enjoy striving for the best photographs possible.

Although Iowa is known more for its tall corn, there are some incredible trees in our state, many of which have yet to be found and measured. Please see the tree measuring guidelines and the nomination portion of the website for the information needed to nominate a tree. If we can get more Iowans to become interested in the biggest trees, the hope is they will become passionate about preserving trees and planting future champion trees. After all, even the biggest champion trees started out as seedlings! With more people involved in the search for the largest trees in Iowa, surely some exciting finds can be made, including new state champions and perhaps even national champions! I hope the listing of “Iowa’s Biggest Trees” will inspire all big tree lovers to join the search for Iowa’s biggest trees!

Respectfully,
Mark D. Rouw
Iowa Big Tree Field Representative