Measuring the Great London Planetree: 2021

Our first visit after arriving in Walla Walla was to the Department of Parks and Recreation. We were told of a relatively unknown London Planetree that was “untouched,” a rarity in Walla Walla.

Two and a half years later, on September 25, 2019, the new Jeannette C. Hayner Park was dedicated, with the monumental tree as the meditative focal point of this lovely pocket park.

Filmed for Earth Day, 2021

There are any number of ways to measure trees. In 600 BC Thales of Miletus established the height of the great pyramid using its shadow; his measurement is accepted to this day. For decades Boy Scouts have been using shadows and pencils to measure tree heights. Today foresters around the world use clinometers or laser rangefinders. These are all simple, non-invasive methods to achieve measurements without harming the tree.

Nikon Laser Rangefinder

Suunto Clinometer

For Earth Day 2020 Tree People of Walla Walla invited two foresters from Umatilla National Forest to join us in measuring the tree. Tree People measured the tree at 129′ with our Finnish Suunto clinometer. Both foresters, using lasers, measured the tree at 127′

Measuring the tree for Earth Day, 2020

We measured the tree again on Earth Day 2021. The tree had grown 4 feet in one year, and now measures 131′ The girth is now 27’9″. The crown spread is 134′. Using American Forests’ formula to measure trees the Jeannette C Hayner London Planetree has a score of 498 points.

The global challenge

Deciding which of the great London Planetrees in the world is the greatest is complicated by two facts. First, American Forests, the register of champion trees in America, considers only native trees, and therefore the London Plane is excluded. And second, The Tree Register, the official register of champion trees in the U.K., does not include measurements of the crown spread. Monumental Trees, a global register, likewise does not include crown spread measurements.

There are a few London Planetrees (in England and in France) taller than the Jeannette C Hayner tree, but we are not aware of any with the combined height, girth and crown spread of this tree. In addition, at just over a hundred years old, this is a young tree and is still growing, adding both height and girth.

We have sent this challenge to the tree community worldwide, and ask you to help us by forwarding it to others we may have missed. We invite communities from around the world to measure their monumental London Planetrees and compare the results.

How to Measure a Tree

Trees which have been pollarded or which have fused or multiple trunks should not be considered.

There has long been a deceptively easy formula for calculating the overall size of a tree. The formula is:

Circumference (inches) + Height (feet) + Crown Spread (feet) = Total Points, THUS:

1 point for each inch in circumference, plus
1 point for each foot in height, plus
1 point for every 4 feet in average crown spread.

The directions for measuring circumference and height are straightforward; to achieve accurate measurements for crown spread, measure the widest crown spread, the narrowest crown spread, take the average and divide by 4.

There are a multitude of complicating factors. and trees on slopes, with multiple trunks, or trees with off-center crowns require special attention.

For the 86-page Measuring Guidelines Handbook by American Forests, click here.

For the USFS White Paper on measuring by David Powell, former coordinator of the Umatilla National Forest Big Tree Program, click here.

(With thanks to Robert Van Pelt, Washington State Coordinator for the National Big Tree Program.)


1: To read the comments offered by Wade Smith, Superintendent of Walla Walla Public Schools, at the dedication of the park, click here.

2: To read a history of 355 Reser Road and the London Planetree, click here.

3. The scientific name of the London Planetree is in dispute. Trees and Shrubs Online lists the tree as Platanus x hispanica. Other sources prefer Platanus x acerifolia. The account below has been referred to an “origin myth” by some.

By 1636 John Tradescant had introduced both the Platanus occidentalis (American Sycamore) and the Platanus orientalis (Oriental Plane) to his garden in England. The hybrid offspring (the London Planetree) was recognized as a species (Platanus x acerifolia) and a century later was being exported back to the colonies. An eloquent account of all three species (as well as the Sycamore Maple) can be found in “The Sycamore Grove, Revisited” by Catherine Hatinguais. Click here.

4. A contender for the greatest London Planetree is the tree at Mottisfont Abbey. View here. As noted by Chengappa (here), it’s possible that the massive trunk is due to two adjacent trees growing with a fused trunk.

A Special appeal:

Tree People of Walla Walla reminds the stewards of our urban canopy that mature trees should not be trimmed or pruned (with the sole exception of The Four D’s).

This rule applies especially to our monumental trees, which are a special gift to our communities.

(This page was revised and edited on April 22, 2021)