leaving the cave of ancient arboriculture(2)

Leaving the Cave of Ancient Arboriculture: a look at common tree myths in Hawai‘i

Undergraduate SeminarFall 2008

5 Objectives or “Hopes”• 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, 4th grade

___________________________

Origin: 1820–30; < LL mythos < 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 personthe 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

the half-truth: pruning• pruning is the removal of plant parts –

usually shoots and branches, but sometimes buds, roots, and even flowers and fruits

• pruning can enhance plant appearance and safeguard plant health and well-being.

• pruning can control plant size (if done properly)

• pruning can increase the health and appearance of trees.

• pruning can influence flowering, fruiting, and vigor.

“a good doctor understands dose!”

___________________________ 1. The internodal removal of a leader trunk

or parent branch.

topping [top-ing]

__________________heading [hed-ing]

1. Cutting a currently growing or one-year oldshoot back to a bud.

2. Cutting an older branch or stem back to a stub or tiny twig.

…defined

Topping stresses trees*Often anywhere from 50 – 100% of photosynthetic leaf areais 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 Compartmentalization of Decay In Trees

CODIT – CCompartmentalization ompartmentalization OOf f DDecay ecay IIn n TTreesrees

• 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 TreesCompartmentalization 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


• Wall 3 is also already present at the time of injury. Wall 3 consists of the parenchyma rays located on either side of the injury (two walls). Wall 3 prevents the lateral spread of decay in the tree.


Wall 3

Wall 3


• Wall 4 consists of the new xylem that is produced by the vascular cambium after wounding to prevent the outward spread of decay.


Wall 4

Wall 4


Callus formation & Compartmentalization

We often say wounds that have strong callus

formation are well “healed”

A tree may appear well ‘healed’ from the outside,

…but in fact extensive decay may exist internally…


Closure and Compartmentalization are 2 different processes

After 17 years, the wound did not close.

Very little decay spread inward.

Tree Anatomy – “Branch Attachment”

How are branches so strong? They are not structurally connected to the trunk!


Tree Anatomy – “Branch Attachment”____________________________________________________________

Darker colored tissues represent branch tissue.

Lighter colored tissues representtrunk tissue.

Represents 3 growth rings pulled apart



Tissues turn abruptly at the branchbase.

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 andtrunk are structurally connected.



A series of steps…_____________________________

1. Branch tissues slow their growth rate

2. Trunk tissues increase growth rate and begin to grow over branch collar

3. Trunk tissues form a collar over the branch collar

4. These steps repeat themselves, forming an overlapping “ball and socket” type connection.



Nature’s engineering….

This image shows a longitudinal dissection, illustrating branch and trunk tissues overlapping


“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)



Two types:2. Adventitious buds that form anew, de novo, within the cambium, usually after some injury (Shigo, 1991)



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.


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!


Demystifying Included Bark

Tissues have turned ‘inward’, evidence of a weak union

1. The vascular cambium turns ‘inward’ within the branch-trunk crotch.

2. The branch bark ridge also turns inward

3. Trunk cylinder (collar) and branch cylinder (collar) both expand

4. Inturned cambium becomes a wedge between the two cylinders.

Solutions & options__________________________________________________________________

Cabling and Bracing

Pruning

Removal

Solutions & options

• 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).

__________________________________________________________________

Solutions & options__________________________________________________________________

• Remove and Replant

Select the Right Tree for the Right Place!

The Bonsai Myth

The Bonsai Myth• Lion tailing – practice of removing the inner

foliage and branches, leaving growth at the outer one-third to one-fourth of the canopy.

The Bonsai Myth

Rule of Thumb – 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.

Solutions & options

• 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.

__________________________________________________________________

Industry Standards• ANSI A300 - The standards dictate the

requirements and recommendations of the tree care industry for satisfactory performance of tree care maintenance.

Operations Construction LightningPruning

Certification

ResourcesInternational Society of Arboriculture (www.isa-arbor.com)

Trees are Good (www.treesaregood.com)

Aloha Arborist Association (www.alohaarborist.com)

ReferencesAnderson, L.M. and H.K. Cordell. 1985. Residential property values improve by

landscaping with trees. S.J. Appl. For: 9:162-166Clark, 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. 17:276-284Reefhof 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.

2008 ISA Conference – St. Louis, MO


Dr. Steve Sillett’s research at Humboldt State University, California

leaving the cave of ancient arboriculture(2)

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