Texas Tree Trails©

A  Geographic Guide To Texas' Significant Trees

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Our Mission is to find and catalog each of these treasures in order to preserve their integrity for future generations - before they all disappear.
Texas A&M Forest Service

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Cross Timbers Urban Forestry Council

Who We Are
The Texas Tree Trails organization is a cooperative effort of the Texas A&M Forest Service, the Texas Historic Tree Coalition, the Trinity Blacklands Urban Forestry Council and the Cross Timbers Urban Forestry Council, among others.


Champion/Big Tree    Historical/Heritage    Species Significant

How to Measure a Champion/Big Tree

The Standard

The accepted measurement criteria in use by the forestry and tree management industries make use of established methods to normalize measurement rules and technique thus providing agreeable results for all parties. Though sometimes inaccurate, field estimation techniques typically are used in place of other more sophisticated techniques due to innate variables in measurement such as the crown spread in different seasons, the slope or rise of the ground in the measurement area or, more often, variations due to the "measurer". The standard error for each widely used measurement technique is fairly similar. For instance, camparing the stick method of height measurement versus smaller, handheld clinometers results in very small standard deviations in the error comparison.

Simple, manual field techniques are as good for most practical purposes as are the sophisticated methods by providing equally acceptable results within the limits of error. Texas Tree Trails opts for the simpler field methods (KISS Methodology). We also follow established measurement rules and guidelines set by American Forests and the Texas Forest Service.

Experience has shown that when indirect methods are used to measure height (as opposed to the direct methods - climbing, using height sticks), measurement from two independent positions is essential (preferentially on a flat grade). The readings from the two positions should agree within the limits of experimental/measurement error. This is an absolute check on instrument and operator error (sighted to correct tip, etc.). Thus, differences of up to 1 m in readings for a 40 m tree are acceptable - precision of hand-held instruments under forest conditions is no better than this.

Texas Tree Trails Champion/Big Tree Measurement Criteria  

Tree Index

To measure a tree for possible inclusion in to the National, State or DFW Big Tree Registries, three static measurements are required:

The trees "index", or normalized comparison factor with no units, is obtained by calculating the sum of  the circumference in inches, the height in feet and 1/4 the average crown spread in feet.

  Circumference + Height +1/4 Average Crown Spread = Total Points or INDEX 

Champion trees within five points of one another are considered co-champions.

Recorded Values

All recorded measurements should be rounded down to the nearest whole number (i.e. 48.9 feet is recorded as 48 feet, or 132.6 inches is recorded as 132 inches).

Ten-Year Rule

Trees must be re-measured at least every 10 years to maintain their “champion” status. This does include photographs and visual inspection by an arborist or forester.

What Is A Tree?

Each specimen nominated for the Texas Big Tree Registry must meet the following definition: “Trees are woody plants, having one erect perennial stem or trunk at least three inches in diameter at breast height (DBH, or 4˝ feet), a more or less definitely formed crown of foliage, and a height of at least 13 feet” (Little, 1979). For low-forking specimens, this means that one of the forks must exceed 9˝ inches in circumference at 4˝ feet to qualify (see image A).

One Tree or Two (or More)?

In practice, it must be determined whether a tree has a single trunk or whether it represents two or more stems growing very close to one another. Trunks that have clear separation(s) or included bark at or near the ground line should be considered separate trees; trunks of different species should also be considered separate stems, no matter how closely aligned. When following the circumference rules below, if the point below the lowest fork places the measurement at the ground line, the stems should be considered separate.



General Rule: Record the smallest trunk circumference between the DBH point (4.5 feet) and the ground, but below the lowest fork. Also record the height above the ground, in inches, where measurement was taken (images B & C).

Image B

Image C

Determining DBH Point

Imaged DTree on Slope: Measure up 4.5 feet along the axis of the trunk on high and low sides; DBH point is midway between these two planes (D).

Leaning Tree: Measure 4.5 feet along both the top and undersides of the trunk; DBH point is midway between these two planes (E).

Image E

Low Branches:
When determining where on the trunk to measure circumference, ignore portions that do not form part of the tree's crown, such as dead branches or forks, and epicormic sprouts.

Obstruction at DBH: If there is a bump, burl, branch, or other obstruction at the DBH point, measure circumference above and below the obstruction and record the smaller value. A buttress that forms between trunk and root system as a natural feature of the species (e.g.—bald cypress, water tupelo) should not be considered an obstruction.

Tree Height  

General Rule: Record the vertical distance between the ground line and the tallest part of the live crown, in feet. Also record the method used to determine this value. (Choices include: direct measurement [telescoping pole, climbing], clinometer, hypsometer, relascope,ultrasonic rangefinder [w/ or w/o internal clinometer], stick method, pencil method, comparison, and wild guess.)

Leaning Tree: Height is not measured or estimated along the length of trunk.

Stick Method; Recommended Methods for Beginners:

Image FThere are many tools that can be used to estimate the height of a tree, but the simplest way uses little more than a ruler or pencil, good eyesight, and a friend!

One person stands near the trunk of the tree and the second person stands at a distance where both Person 1 and the top of the tree are visible. Person 2 holds a ruler (or pencil) upright at arms length and (carefully!) walks forward or backward until the entire length of their ruler covers the tree from base to top (F)  while holding the ruler at arms length, Person 2 turns their wrist right or left so that the ruler is now horizontal, with one end sighting the base of the tree. Now Person 2 instructs Person 1 to move away from the trunk in the direction the ruler is pointed (at a 90 degree angle) until they are standing where the end of the ruler points (G). Image GPerson 1 is now standing roughly the same distance from the trunk as the tree is tall. Use a tape measure to record this distance, in feet.

The image below shoes a field technician making a tree height measurement using the "stick method". Height estimations are based on the simple geometric formulas of Similar Triangles.

Similar Triangles for the Stick Method,

  B = A * b/a 

(Where A, a and b and the technician's height are known distances; A is calculated from the Pythagorean theorem where A = the square root of [field technician's height + the distance to the tree base]. )

Pencil Method

There is also another technique known as the “pencil” method.  For this you can use your pen or pencil, or anything of similar shape and size. In this method it is not important that the length of the stick above your hand on your outstretched arm is equal to the distance from your eye to that same point of the pencil where it is held in your hand. Simply hold out the pencil and move toward or away from the tree until the top of the pencil is lined up with the tree’s highest point and the bottom of the pencil lines up with the spot directly below that highest point. Then turn your hand so that the pencil is “laid down” on the ground, keeping the bottom at the same point. Visually mark the location where the top of the pencil now is found on the ground out away from the tree (It helps to have a second person for this purpose). Tree height should be equivalent to the distance from the pencil bottom spot to the new pencil top spot as long as that point is at a right angle to you!

Using a Clinometer

State Forester Matt Grubisich assists with the use of a Suunto clinometer at a volunteer traniing sessionA clinometer is a relatively simple mechanical device for measuring height of trees in the field by taking sight measurements and applying trigonometry to measured angles and known distances to calculate height.

One technique for specific type of instrument, the Suunto Clinometer, follows:

  1. Measure the horizontal distance from the base of a vertical tree (or the position directly beneath the tree tip of a leaning tree) to a location where the required point on the tree (e.g. tree tip) can be seen.
  2. Sight at the required point on the tree:

    • Using one eye: Close one eye and simultaneously look through the Suunto at the scale and 'beside' the Suunto at the tree. Judge where the horizontal line on the Suunto scale would cross the tree.
    • Both eyes: With one eye looking at the Suunto scale and the other looking at the tree, allow the images to appear to be superimposed on each other and read where the horizontal line on the Suunto scale crosses the tree. Note: If you suffer from astigmatism (a common situation where the eyes are not exactly parallel), use the one eye approach.

  3. Read from the percent scale and multiply this percentage by the horizontal distance measured in step one.
  4. Site to the base of the tree and repeat steps 2 - 3.
  5. Combine the heights from steps 3 and 4 to determine total tree height:

    • Add the 2 heights together if you looked up to the required point in step 2 and down to the base of the tree in step 6.
    • Subtract the height to the base of the tree from the height to the required point if you are on sloping ground and had to look up to both the required point and the base of the tree.

  6. Check all readings and calculations. Click for a simple diagram on How to Use a Clinometer. Courtesy Ben Meadows, 2003
Simple Ratios Method (or fun with math)

using the ratio methodFor some this may be the easiest method but requires two people - the measurer and the measuree. Measure the actual height of one person and record that height in feet and inches (5 feet, 6 inches). The "measuree" person stands beneath the tree below the highest point.

The "measurerer" holds a yardstick perpendicularly outward from their body as in the Stick Method, but sights the "measuree's" full height between two convenient measurements locations on yardstick, say between 5 and 8 inches. That would mean the measuree's full body height is equivalent to 3 inches on the yardstick at that distance from the tree.

the measurerersThe measurer without moving their arm or yard-stick, carefully walking forward or backward, sights the topmost point of the tree by tilting their head back and reading the inch marking for the tree top, for example 27 inches. Write it down. This measurements indicates the tree is equivalent to  27 minus 5 inches or 22 inches on the yard stick at the same distance from the tree.

Using a simple ratio formula we can calculate the tree height.

Calculating (measuree height/3) is equivalent to (tree height/22) but we know the measuree height so we will put that value into the formula (5.5/3)=(x/22). Cross multiply (5.5*22)=(3x) and solve for x = 40.3 Feet

The formula for a calculating the tree height is:

    (5.5/3) = (x/22) or x = 40.3 Feet 

DIY Citizen Forester Method of Tree Height Measurement

As an alternate and simple tool for measuring tree height, Marilyn Sallee, of the Spring 2006 Citizen Forester Pioneer Class made a DIY (do-it-yourself) tool out of everyday materials and offered to share it with everyone.

Great engineering! I particularly like the plumb line which keeps the tool at right angles; the way it should be so the remaining angles and measurements can be accurate. Thanks, Marilyn!

The list of materials include:

  • 8-1/2" x 11" sheet of heavy paper
  • 8-10 inch piece of string
  • small weight, bead or button
  • fat soda straw
  • tape or glue
  • pencil or awl to poke two holes in paper

The Instructions, a diagram and details of use are detailed in Citizen Forester Tree Height Tool PDF.

Average Crown Spread  

Measuring Crown Spread

Image HGeneral Rule: Along the drip line of the tree (H), two measurements of the crown width are taken and recorded (in feet), at right angles to one another. The first is the widest crown spread (I), which is the greatest distance between any two points along the drip line. Once the widest spread has been found, turn the axis of measurement 90 degrees and find the widest crown spread in this plane (J). The two crown spread measurements are averaged for use in the tree index formula.

Drip line: This is the outline on the ground of the outermost leaves of the crown (H). Only live portions of the crown are included.

  Average Tree Crown = (Major + minor) / 2 

Image I

Image J


Tools and Skills Required 

Recommended Tools

Yard/meter stick (required) camera (required)
measuring tapes (required, see Forester) cell phone (recommended)
clipboard/forms (required) clinometer (optional),
writing utensils (required) portable GPS (recommended)

Recommended safety equipment: hard hat, work gloves, work shoes, coveralls.

ID Badge: Contact Doug Pierson for a Tree Trails Associate badge with photograph for identification including clear-vue plastic pouch with shirt pocket/collar clip. He will need a good quality "head and shoulders" photo emailed to him to add to your badge.

Recommended Skills

Master Naturalist or Master Gardener training is helpful; college level silvics, botany or similar; comfortable with geometry and simple algebra; must be able to deal directly with the public, the citizenry of the Metroplex; able to walk around outdoor areas in most any terrain measuring trees; willing to take ownership of his or her part in this project and carry the message to others.

Classroom instruction is offered periodically by local state foresters and regional certified arborists where basic tree identification, regional tree knowledge and hands on field measurement techniques are taught. There is an indoor instructional lecture with plenty of time for questions and answers followed by a field trip to a regional park to measure trees. Volunteer Training sessions are announced in advance on the Announcements page. Many of the photographs on this web site were taken at volunteer training sessions. Registration is required.

classroom lecture - tree ID and measurement state foresters instructs trainees on proper techniques for measuring circumference of multi-trunk trees
classroom instruction field trip, hands on training

Data Collection 

The standard data set to be used is that established by the Texas Forest Service. An example of the data set can be seen on the the DFW Champion & Big Tree List as one row beginning with the tree ID. Each data record is comprised of data fields that make up the standard data set for each tree detailing it's name, description, unique location and characteristics.

A quality set of photographs must be recorded for the tree being investigated representing color, relative size, shape and any other unique characteristics. A minimum of one vertical photo with the entire tree in view (important!) plus a series of other horizontal shots highlighting leaves, fruit, bark, form, unusual characteristics, flowers, structures, damage, roots, trunk, etc. are needed to complete the data record.

Notes, sketches, botanical observations, observations on the trees health, evidence of damage, potential hazards, placement in relation to surroundings (geography), soil, wildlife usage, etc. All are helpful information.

The format of collection, method of collection and mode of delivery is described in detail in the Texas Tree Trails User Guide Chapter 2, Data Management. The User Guide in it's entirety including all information regarding form usage and submission, Volunteer training, help and the user forms for field measurements and data submission are available on the Tree Trails Documentation page.  If you have questions regarding the documentation or forms and their usage, contact Doug Pierson for assistance.

Note: It's a good idea to take one of the Tree Trails training sessions to get a full understanding of all the processes involved. Contact one of the board members to sign up for a training session. (See the Contacts page.)


Historic/Heritage Tree 

See the Texas Historic Tree Coalition web site.

For this category, all criteria required for Champion/Big Trees apply plus a historical research summary and supporting data as to why this particular tree is Historically Significant with corroboration from known reputable historians or researchers to back up this claim.

To meet all requirements for addition to the DFW Historic Tree Registry the following additional data is required:

  1. A Historic Narrative relating the tree to a significant place or person in time more than fifty years in our past with sufficient detail to tell the trees story or the historical events during the trees life.
    Often times the tree, in a place during a time of our history, stands as a WITNESS to significant events or a person's involvement in these events and withstands the rigors of time to remain with us to this day. These "Witness" trees can tell a narrative story of many significant events that happened through out time at that particular place.
  2. The Historic Narrative Summary to summarize in a phrase or sentence the historic significance of the tree or the events the tree witnessed.
  3. The Historic Narrative Bibliography or Tree History Bibliography listing reference books, newspaper articles, family histories, photographs, etc. that contribute to the verification of the tree's historic status.
  4. Any additional Information that you believe might be valuable in determining the tree's historic status.
  5. Photographs of the tree and the historical events
  6. Registration and confirmation of the tree as a true historic icon by the TXHTC.

Please refer to TXHTC for the complete process of Historic tree registration. The only process from Tree Trails perspective is to nominate your tree first with the physical and location data. Then the nomination form will be forwarded to TXHTC for approval. The remainder of the process will be handled by their organization.

A sample historic tree record is shown with the Quincentennial Bur Oak in Plano. Note that this is a sample of a prototype format. The current format may be different. IMTs or Indian Marker trees are fully managed by TXHTC.

Species Significant 

For these categories, all criteria required for Champion/Big Trees apply plus a technical report as to why this particular tree is Significant with corroborated data to back up this claim. The data must be confirmed by a regional forester to be official.

Note: Please record Significance data in the "Special Notes" data field. Important! Do not use any punctuation other than a period, comma or dash. Please keep it very brief as space is limited.


  To Read More ...

Measuring Tree Height with an Abney Level

American Forests' Big Tree Measuring Guide

More Advanced Methods for Tree Height Measurement

The National Arbor Day Community Tree Contest Teacher and Student Activity, measure trees


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