Agriculture Reference
In-Depth Information
Figure 2.10
Too many branches originate from too small
an area of trunk, even though some of the angles are wide
and stable. Early pruning could have prevented this tragic
result.
Figure 2.11
This advanced birch tree has been fastened
to a wire in the nursery. The subsequent damage and
swelling makes this a weak point on the tree.
might be right but the trunk cannot support
so many branches in almost the same spot.
The pressure exerted in high winds is too
great to be sustained and eventually branches
are lost, hopefully without harming people or
buildings. Engineering in trees is just as
important as it is in buildings.
The trunk should also be thickest at the base
and then taper to the top. Some advanced
trees have been fastened to wires to keep
them upright. Often the thickest part of the
trunk can be at the point it was tied to its
support. This can also be a point of weakness
in the future (see Figure 2.11).
Trunks
The thickness of the trunk (or trunk
calliper) is also a good indicator of ultimate
stability. Trees with thick trunks in relation
to their height have generally been
grown at wider spacings in the nursery,
allowing for a denser canopy of leaves that
will support speedier root growth and
therefore quicker establishment. A short and
stocky tree with a low centre of gravity may
not be elegant, but it is stable. Just think of
those rocking children's toys that refuse to
be pushed over.
PLANTQUALITY
• Good selection is most important with trees
• Right proportion of roots to shoots
• Roots should not spiral
• Healthy roots are white and fibrous
• Plant is stable in its pot
• The trunk tapers evenly from bottom
(widest) to top
• Branches evenly spaced
• Wide angles between the branch and the
trunk
