Background Glossary Books
page contains many resources to support you in the study and
understanding of Arboriculture. You’ll find background information, a glossary,
a list of books & publications, as well as a list of links
to other arboricultural web sites. Use the links in the menu
above to access the different sections, or simply scroll down
A Little About Trees in the Urban
Trees are some of the oldest and largest
living things on earth providing great pleasure and many benefits
to man. To understand why we need to care for trees and what
kind of care they need, it is a good idea to start with understanding
the difference between trees in their natural habitats and trees
in the urban landscape.
Trees evolved as grove organisms existsing
in cooperative groups. Trees that grow in a forest, or in a
group, are under much different conditions than those which grow
in an urban environment. A forest by definition is a whole ecological
system where trees and other plants, animals, and organisms
support each other ecologically.
When a tree grows as a solitary individual,
the conditions are dramatically different. It no longer has the
same support and protection of other trees and organisms, and
its growth and behavior are unlike those found within a
natural habitat. There is the added influence of roads, buildings
and unnatural landscapes created by man.
An experienced arborist is necessary in
order to ensure that the tree is safe and healthy to survive
in the urban environment. Having knowledge of a tree's origin
and natural habitat helps in understanding some of the problems
it may have, or how to either eliminate or reduce those problems.
It is essential to take note of the fact that the label Tree
Surgeon, as used in the past, is now outdated. Indeed, scientific research
by Dr. Alex Shigo and others has shown many
of these obsolete practices to be harmful to the long term health
of the tree.
Plant Health Care
The International Society of Arboriculture (ISA) was formed in
1924 to foster research and education worldwide for professionals
in the tree care industry. Plant Health Care (PHC) was developed
in the 1980s to provide a more holistic approach to maintaining
the care of trees and other plants in the landscape. The
focus is upon the plant rather than specific pests or disease,
and the key is a broad base of knowledge. This is a field
which is changing every day as more research is done in
the field of arboriculture.
Based on the information that has come
about in arboriculture, the ISA has developed standards for
proper pruning and care of trees as well as safety guidelines.
For example, in addition to being unsightly, improper cuts
on trees can lead to serious future problems. To prevent this, Natural
Target Pruning is employed. There are many other rules
and guidelines for the proper care of trees and shrubs.
Things have changed a great deal over the years in the tree care
industry. With a little research and investigation, one can
feel confident that their trees will be taken care of appropriately.
Please use the links on this Web site to gain more knowledge
on arboriculture. The International Society of Arboriculture web
site for consumers is particularly useful.
science and art of caring for trees and other woody plants.
Bark Ridge: The point just outside the branch
collar at the base of a limb is the branch bark ridge.
Collar: The swollen area or shoulder, where
the branch joins another branch or trunk of the tree. This
is the protection zone of the branch and should
not be violated.
Cloud Pruning: Pruning
limbs in such a way as to create space between them and flatten
the top and bottom. An example would be the work done in Japanese
gardens, where one can see the appearance of clouds.
to the canopy of the tree, which includes all the limbs from
the bottommost to uppermost part of the tree.
training of trees or shrubs to grow flat against a wall or fence.
This is best started when the plant is young but sometimes an
older plant can be directed, to some degree, in this fashion
if done with care. There are many styles, formal and informal
term we use to describe basic pruning on a tree, also called “crown
cleaning.” This includes removal of dead, diseased, damaged,
and deranged, (crossing and crowded), material in the tree. We
call it the Four Ds.
Target Pruning: Aiming at making the cut just outside
the branch bark ridge so that
the branch collar is not violated and at the same time a stub
is not left.
technique of pruning back yearly growth on a tree to maintain
a given size and appearance. Pollarding should
be started when the tree is very young, and should not be confused
a very old form of pruning where trees or shrubs are shaped or sculptured into
geometric shapes, animals, birds, or other things. The shaping
of a hedge to achieve and maintain certain shapes or angles to
fit a particular landscape architecture could be considered to
to be confused with pollarding. Topping
is the process of cutting back limbs to a stub, with
very little or no remaining foliage left on the tree. This is
very detrimental to the tree and in the long run ends up costing
to the mass of the tree being affected by mechanical wind force.
An overly dense canopy acts like a tightly woven sail in resisting
the wind’s force.
Books and Other Publications
Dr. Alex Shigo
A basic outline of tree anatomy and physiology.
Dr. Alex Shigo
A book that is easy to read and easy to understand, with many
photos on the correct pruning of trees.
Stupsi Explains the Treeby
A cartoon book that explains the structural mechanics in trees
in a simplistic and simple way for the layman.
Trees - The Visual Guideby
Allen J. Coombes
A softcover field guide with more than 500 species of trees
from around the world with color pictures.
Trees for Urban and Suburban Landscapesby
Edward F. Gilman
A very comprehensive guide for selecting the right tree and how
to care for it. It has details on over 1,000 species of trees
in North America.
Pests of Landscape Trees and Shrubs
- An Integrated Pest Management GuideUniversity
of California publication #3359.
A wealth of information to help maintain healthy landscapes.
Links go to external web sites
and will open new windows.
Some web sites may not always be available.
Society of Consulting Arborists (ASCA)
Oak Mortality Task Force
for Urban Forest Research (Report, PDF 4.8 MB)
Friends of the Urban
Society of Arboriculture (ISA)
Society of Arboriculture
Tree Care Industry
Education and Philosophy by Alex L. Shigo
ISA- an excellent site for more info about tree care.
Links to more Arboriculture
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