Single and Multi-stemmed Definition   Edward Frank
  Jul 17, 2007 18:56 PDT 

The question arose as to how we differentiate single stemmed or (single 
trunked trees) and multi-stemmed (multi-trunked) Trees.  The way we classify 
or sort them depends on their character at ground level. If they have a single
stem, with a single pith at ground level, this is a single trunked tree. If
they derive from a single root mass but have multiple stems, each with
separate piths at ground level, then it is a multi-trunked tree. A fusion
of two trees with separate roots is just that a fusion of two separate
trees. Coppices become more complicated. Then you have examples of hundreds
of acres of cloned aspens all derived from root spreading underground. I am
not sure how to demarcate the dividing line between multi-trunked trees and
coppices, or coppices and clonal groves. I have ideas, but the ENTS group
discussions never got that far before it fizzled.

Multitrunked Playanus occidentalis - trunk with tape.  Pith trace in black and seam where two trunks gew together.  This tree is the former national champ sycamore in Ohio!!!!! You can even see a seam to the ground……. photo by Will Blozan

For listing purposes in standard champion tree lists, each trunk with a
separate pith at ground level should be considered a separate tree. When I
get several other projects out of the way, I plan to develop a section on
multi-trunked trees and create a list for multi-trunked trees based upon
total cross-section area of all stems at breast height, maximum cbh for any
one stem, maximum tree height, total spread of the clump, and perhaps
derived approximation of crown volume. As the current situation exists we
are faced with the peculiar possibility that a single multi-trunked tree
with large trunks might appear on a champion tree list multiple times, one
for each of the large stems.


Re: Single and Multi-stemmed Definition   DON BERTOLETTE
  Jul 19, 2007 13:27 PDT 


I liked how definitive your pithy definition between single-stemmed and multi-stemmed trees depended on what was happening with the pith at ground level.

My forestry bias will show right away in the following question:
Given that Tree "A" has a single pith at historic/current ground level, and its pith 'forks' at 2.5' above h/c ground level, 1)is this considered a single stem? and 2)where do you measure its circumference/diameter?
Given that Tree "B" has a single pith at historic/current ground level, and its pith 'forks' at 6.5' above h/c ground level, 1)is this considered a single stem? and 2)where do you measure its circumference/diameter?


Re: Single and Multi-stemmed Definition  Edward Frank
  Jul 19, 2007 13:27 PDT 


If the tree has a single pith at ground level but branches or splits at 2.5 feet, then according to the Tree measuring Guidelines of Eastern Native Tree Society "Some trees, like flowering dogwood or rhododendrons, may branch well below 4.5 feet but have a single pith at ground level. In the case of such trees, I would measure the narrowest point below the lowest fork." I believe this would apply regardless of the species, at least in my opinion it should. American Forests has a similar guidelines: "If the tree forks record in inches the smallest circumference between 4˝ feet and the ground below the lowest fork excluding dead branches and epicormic sprouts. Also record the height above the ground line where measurement was taken, in inches. " These definitions are appropriate. 

Both A and B would be considered single-stemmed trees 

The girth of Tree A would be measured at the narrowest point below the "fork" and that value and the height above ground at which it was measured would be recorded. 

The girth of Tree B would be measured at 4.5 feet above ground level. If there is a burl or other distortion at that height the girth would be measured at the narrowest point below 4.5 feet, and if that was impossible, then immediately above the distortion. 

The problem comes when 1) these low branching trees have the separate branches below 4.5 feet but they have become fused into a single stem; 2) when there may be multiple piths at ground level but you can not tell for sure; or 3) when there are multiple piths but the stems have fused to a height above 4.5 feet. In cases such as these likely best compromise is to measure the fused trunk at 4,5 feet and note the fact this is a fused stem of a low branching tree or fused multi-stem tree. This is what Larry has been forced to do in some cases. 

Ed Frank

RE: Single and Multi trunks    Edward Frank
   Aug 17, 2007 07:21 PDT 


This is the thread of the discussion Don and I have been having on the
subject. I thought I would post it to the discussion list.....

Ed Frank

Sent: Monday, August 13, 2007 11:21 PM
Subject: RE: Single and Multitrunked trees


Noting that there appears to be a water line some 12 inches above
CURRENT ground level (no pun intended), I'd want to ask the question
often posed of sycamores around Hatfield MA...are we seeing the tree's
trunk some distance up it, or are we actually near the root collar. In
the absence of a clearly defined and accepted rule, I would still
measure 4.5 inches above root collar, unless there were special
circumstances about the tree that mitigated for a different measuring
point (butt swell, buttressing, burls, etc., come to mind).

Given that Will's tree with pith delineations had a root collar at
current ground level, I would suggest that there are three separate
trees there. I would start out measuring dbh/circumference, at 4.5 feet
above looks like the larger tree might have some
burls/deformities that might 'get in the way' of an accurate
measurement, in which case, I'd measure the dbh/circumference until I
got a 'minimum reading', say within a foot or two of breast it becomes a judgement call, a 'swag' if you will.

Now for the fun of it, let's "what if" a scenario, where it turns out
that this tree's base is actually 12 foot under current ground level,
and the piths of all three trees intersect about 5.5 feet above our
"what if" tree's actual base. Here you'd have ONE tree forking a foot
above breast height...right?



From: "Edward Frank" <>;
Subject: Re: Single and Multitrunked trees
Date: Tue, 14 Aug 2007 19:32:56 -0400


I have been talking about current ground/supporting surface upon which
the tree is growing because I want a definition that does not require
any interpretation by the person doing the measuring. They do not need
to determine if it is buried by several feet of extra dirt, if its roots
are exhumed, if it grew on a nurse log, or started on the side of a
boulder that has since rolled away. If there is some interpretation
that can be easily made, that can be included in the description along
with what the measurer believes to be a more appropriate girth, but the
base measurement should be based upon a criteria that does not require

I am still bothered by rely fat trees on steep slopes, but I could not
get anyone to offer or agree to an alternative base point for girth

Ed Frank

----- Original Message ----------------------------------------------------------
Sent: Tuesday, August 14, 2007 11:21 PM
Subject: Re: Single and Multitrunked trees


I have been in the same 'grapple' and not arrived at a satisfactory

At the accuracy level that we are measuring tree heights (to the tenth
of a foot, or something slightly more than an inch). to not require
expertise in judging where the root collar is, seems

I can't think of a more definitive and correct way to measure height of
a tree, than from where it's root system ends...commonly known and
reasonably easily determined, as a root collar.



From: "Edward Frank" <>;
Subject: Re: Single and Multitrunked trees
Date: Wed, 15 Aug 2007 23:22:48 -0400


This is how I have arrived at the conclusions I have offered. As I see
it the biggest problem with comparing girth measurements made by
different people is that different people measure trees in different
ways and at different points. Look at photos of how girths are being
measured in some of the champion tree books. Some are at ground level.
Some wrap around two or more separate trunks, others stretch around
branches that stick out at 4 1/2 feet. Even well meaning people trying
to measure the best way have their own interpretation of what is right.
The goal of my designation of 4.5 feet or gbh above the current
supporting ground surface eliminates any interpretation from the
measurement. This will be good for the vast majority of trees that are
measured and assure that these numbers are measured in the same way each
time. There are the exceptions specifically noted in the protocol for
when there are burls or irregularities at that height, or if their are
low branches below that height. In each of cases the protocol say
specifically what should be measured and what numbers should be noted -
including the actual height above ground level and the reason for not
measuring at the standard height. Again there is no interpretation to
create variability between the different people measuring and their

If the person doing the measurement is knowledgeable enough to notice
that the tree is partially buried, or is growing on a nurse log or some
similar anomaly, they are encouraged to make an additional measurement
at what they interpret to be the correct height and note this in the
tree description, but this should be in addition to not in place of the
standard ground level plus 4.5 foot measurement.

This started out from the concept expressed by Colby Rucker of measure
from "where the acorn sprouted."   This seems to me to be a basic and
profound concept. I am not sure the top of the root collar meets this
definition. The transition between basal flair and upper root collar is
from my observations, and I may be wrong often at a higher point that
the original sprout point for the tree. I think the ground surface as
projected under the tree, typically below the root collar, better meets
the "where the acorn sprouted" concept and is to my mind the better

For those interested in root collar information basics and tree planting
there is a nice article on the subject at this address (I have included
an excerpt from one page of the document):

A Practitioner's Guide to Stem Girdling Roots of Trees

Gary R. Johnson
University of Minnesota

Richard J. Hauer
Minnesota Department of Agriculture   BU-07501     2000

Normal vs. Abnormal Root Systems

Root collar examinations are used to determine if root system
abnormalities are impacting a tree. To determine if a root system
abnormality exists, one needs to compare against a normal root system.
Field observation, along with a review of species-specific root system
profiles, will help provide the practitioner with an understanding of a
normal root system. An easy way to observe normal root systems is to
take a walk in the woods. But in general terms, what is a normal or
ideal root system?

Normal root systems are often described as having main (first order)
laterals that radiate from all sides of the stem/root interface (Figure
23). The number of main laterals ranges from a few to more than a dozen.
Trees in forests with a greater number of main laterals than other trees
tend to become dominant survivors in a competitive forest community
(Kormanik 1986). The root diameter of main order laterals decreases
rapidly through the zone of rapid taper into ropelike roots with
approximate diameters of 0.5 to 3 inches. Root spread is usually well
beyond the drip line, commonly to about three times the branch spread
(Gilman 1997).

Fig. 23 - A normal littleleaf linden's root system, showing the larger,
main order roots radiating out from the stem/root interface (root

Most main-order laterals originate from the root collar and parallel the
soil surface at depths of a few inches to a foot or more. Many tree
species also produce oblique roots, which grow at a sharp angle into the
soil and stabilize trees. Sinker roots grow downward from lateral roots
on approximately 75% of tree species, function in support and
absorption, and usually are located within 6 to 10 feet of the stem.

From main-order laterals arise secondary and tertiary woody and nonwoody
roots, which magnify the absorption of water and nutrients. These roots
proliferate in zones of favorable moisture and nutrition. Most exist
within the top foot of the soil surface.

Stem diameter normally increases from the top downward. Root flares
and/or stem tapers are common (except in some conifers) due to a growth
pattern in which growth is greater on the top of the root than the
bottom. When trees are planted deep or soil fill is placed over the root
system, this characteristic pattern might not be visible.

Edward Frank



Thanks for the thoughtful response!

I think that you'll find no better definition of root collar than where
the acorn sprouted, as that one inch (plus or minus) most definitively
describes, in "the proverbial nutshell", where the root collar was at
"birth", and would (tree physiology-wise) be at present (barring, as you
say, anomalies such as nurse trees, infilling from flooding, etc.).


RE: Single and Multi trunks   DON BERTOLETTE
  Aug 17, 2007 20:02 PDT 

Just a quick note...this thread started with the image I believe Will had posted of a 'triple tree', which if it were one, was forked below ground level, or if it is three trees, has its root collar below but near ground level.  My questions, comments are of the "what if" variety, intended to stimulate discussion on where to measure tree height 'from'...:>}