To have a better understanding of the tree as a living, dynamic organism
To understand the basic response and defense mechanisms of trees.
To understand why some treatments cause harm to trees.
To learn to recognize common ‘myths’ about trees and to see the trees for what they are.
Exposure to the world of arboriculture.
So, what IS the point? ~~~ learn to see trees for what they are ~~~ The tree which moves some to tears of joy is in the eyes of others only a green thing that stands in the way. Some see Nature all ridicule and deformity, and some scarce see Nature at all. But to the eyes of the man of imagination, Nature is Imagination itself. - William Blake, 1799, The Letters
Trees and Quality of Living ▪ Research shows trees reduce noise pollution by up to 50% (Reethof and McDaniel, 1978) ▪ Increased property values (Anderson and Cordell, 1985) ▪ Stronger sense of community (Dwyer et al, 1991) ▪ Reduction of greenhouse gas emissions , increased air quality (Rowntree and Nowak, 1991)
“ trees are great to climb ; trees give us shade ; dogs love trees for obvious reasons; trees are a necessary ingredient for making a tree house .
… and where else would cats get stuck ? ”
Fiona Day, 4 th grade
___________________________ Origin: 1820–30; < LL mȳthos < Gk mŷthos story, word myth [ miths ] (plural myths ) 1. ancient story: a traditional story about heroes or supernatural beings, often attempting to explain the origins of natural phenomena or aspects of human behavior 2. idealized conception: a set of often idealized or glamorized ideas and stories surrounding a particular phenomenon, concept, or famous person the myth of the new man 3. myths collectively: myths considered as a group or as a genre 4. false belief: a belief or notion based more on tradition or convenience than on facts.
half-truth , haf-truth(n) A statement that mingles truth and falsehood.
Tree Myths We have many ideas about trees. Sometimes they work, …. and sometimes they don’t . What kind of times are they, when A talk about trees is almost a crime Because it implies silence about so many horrors? - Bertolt Brecht, To Those Born Later
Topping stresses trees *Often anywhere from 50 – 100% of photosynthetic leaf area is removed during a single topping treatment. *Topping often initiates expansive columns of decay in both the above ground (branches and trunk), and below ground (roots) portion of the tree (Shigo, 1981).
CODIT – C ompartmentalization O f D ecay I n T rees
Wall 1 is formed by the physical plugging of xylem (tracheids and vessel elements) above and below the injury (two walls). Wall 1 may or may not be present at the time of the injury. Wall 1 prevents the spread of decay upward and downward in the trunk of the tree.
Wall 1 Wall 1 *weakest barrier zone (Photo taken from “A New Tree Biology” Shigo, Alex)
CODIT – Compartmentalization Of Decay In Trees Wall 2 is already present at the time of injury. Wall 2 consists of the annual rings of xylem. This protection zone is responsible for preventing the inward spread of decay. Wall 2 *trees don’t heal they compartmentalize (Photo taken from “A New Tree Biology” Shigo, Alex)
We often say wounds that have strong callus formation are well “ healed ” more myths more confusion A tree may appear well ‘ healed ’ from the outside, … but in fact extensive decay may exist internally… (Photo taken from “A New Tree Biology” Shigo, Alex)
Closure and Compartmentalization are 2 different processes After 17 years, the wound did not close. Very little decay spread inward.
How are branches so strong ? They are not structurally connected to the trunk!
(Photo taken from “A New Tree Biology” Shigo, Alex)
Tree Anatomy – “Branch Attachment” ____________________________________________________________ Darker colored tissues represent branch tissue. Lighter colored tissues represent trunk tissue. Represents 3 growth rings pulled apart (Photo taken from “A New Tree Biology” Shigo, Alex)
Tree Anatomy – “Branch Attachment” ____________________________________________________________ Tissues turn abruptly at the branch base. As the tissues develop downwards, they do mix (intertwine) with the trunk tissues. This area where the tissues ‘mix’ is the only area where the branch and trunk are structurally connected. (Photo taken from “A New Tree Biology” Shigo, Alex)
Tree Anatomy – “Branch Attachment” ____________________________________________________________ A series of steps… _____________________________
Branch tissues slow their growth rate
Trunk tissues increase growth rate and begin to grow over branch collar
Trunk tissues form a collar over the branch collar
These steps repeat themselves, forming an overlapping “ball and socket” type connection.
(Photo taken from “A New Tree Biology” Shigo, Alex)
Tree Anatomy – “Branch Attachment” ____________________________________________________________ Nature’s engineering…. This image shows a longitudinal dissection, illustrating branch and trunk tissues overlapping (Photo taken from “A New Tree Biology” Shigo, Alex)
“ Epicormic Branches and Failure” ____________________________________________________________ Epicormic - “upon the bark” Two types: 1. From dormant buds that are carried along through the wood and eventually may develop to form a branch (Shigo, 1991)
“ Epicormic Branches and Failure” ____________________________________________________________ Epicormic - “upon the bark” Two types: 2. Adventitious buds that form anew, de novo, within the cambium, usually after some injury (Shigo, 1991)
“ Epicormic Branches and Failure” ____________________________________________________________ Epicormic - “upon the bark” Much weaker attachment The latter type of epicormic has a much weaker attachment point, very similar to included bark. Attachments are structurally undermined by pockets of decay where the new branch originates from after ‘topping’. Illustrates V shaped union common with included bark and adventitious growth after topping. Illustrates adventitious shoots after topping. Notice narrow angle of attachment and decay in parent.
“ Epicormic Branches and Failure” ____________________________________________________________ Demystifying Included Bark Branch bark ridge is bark tissue that gets pushed upward within the branch-trunk crotch. A strong branch-trunk union is evident by the BBR pushing ‘upwards’. It’s important to understand included bark to understand the type of connection that often develops after topping!
“ Epicormic Branches and Failure” ____________________________________________________________ Demystifying Included Bark Tissues have turned ‘inward’, evidence of a weak union
The vascular cambium turns ‘inward’ within the branch-trunk crotch.
The branch bark ridge also turns inward
Trunk cylinder (collar) and branch cylinder (collar) both expand
Inturned cambium becomes a wedge between the two cylinders.
Solutions & options __________________________________________________________________ Cabling and Bracing Pruning Removal
crown reduction - Reducing the height or spread of a tree by pruning back the leaders and branch terminals to lateral branches that are large enough to assume the terminal roles (at least one-third the diameter of the cut stem).
Do not remove more than 1/3 of live canopy at one time.
The Bonsai Myth Lion tailing reduces branch taper, leading to higher rates of failure. (Matheny & Clark, 1994) Greatly reduces photosynthetic surface area, often leading to stressed conditions. Increases center of pressure height Permanently alters overall structure of canopy by removing interior growth. Leaves much fewer options for pruning.
Thinning - the selective removal of branches to increase light penetration and air movement through the crown. Thinning opens the foliage of a tree, reduces weight on heavy limbs, and helps retain the tree’s natural shape.
Anderson, L.M. and H.K. Cordell. 1985. Residential property values improve by landscaping with trees. S.J. Appl. For: 9:162-166
Clark, J. and Matheny, N. 1994. A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas. Hortscience Inc.
Dwyer, J.F., Schroeder H.W., and P.H. Gobster. 1991. The significance of urban trees and forests: Towards a deeper understanding of values. J. Arboric. 17:276-284
Reefhof G., and O.H. McDaniel. 1978. Acoustics and the Urban Forest . Proceedings of the National Urban Forestry Conference. USDA Forest Service. State University of New York College of Environmental Science and Forestry, Syracuse, NY.
Rowntree, R.A. and D.J. Nowak. 1991 . Quantifying the role of urban forests in removing atmospheric carbon dioxide. J. Arboric. 17:269-275
Shigo, Alex. 1991. A New Tree Biology. Shigo and Trees, Associates.
Shigo, Alex. 1984. Modern Arboriculture. Shigo and Trees, Associates.