Agriculture Reference
In-Depth Information
Renovating ornamental trees and shrubs
Many ornamental trees can be safely left to
their own devices and may never need
anything more than the removal of dead or
damaged wood or crossed branches. However,
when there are serious structural defects to
correct such as competing leaders pruning
can provide the solution. It is also possible to
make more space under the tree, to reduce
the tree's height or width, or to thin the
canopy to allow better air circulation or allow
more light into the garden. Hacking away at
the periphery of the tree's canopy will only
produce a hedged effect which will destroy
the tree's beauty. This hedging technique on
trees only looks acceptable when the tree is
acting as a landscape group like any other
hedge (see also 'Pleaching', page 94).
Do some reading or check with your
local nursery for plants that thrive in your
garden conditions. Also check that they
are the right height and width for your
needs and will not grow into an
expensive problem by damaging house
foundations.
Once you have made the decision that it is
worth saving, spend some time just looking at
it. Whatever the plant, start by removing any
dead or diseased wood, this clears the way for
the next step. Consider what you want from
the plant. Is it more flowers, fruit, a stately
canopy or space to move around or under it?
Is it a shrub that could be turned into a small
tree? Can you discern a pattern in the
branch structure?
Before removing what appear to be excess
branches, consider what sort of tree you are
dealing with. Is it a shade-loving tree? If you
remove too much material the exposed bark
may become sunburnt. Is it a conifer? Most
conifers do not grow from old wood, or wood
that carries no leaf or green parts. Once the
green parts are removed the branch will
never regrow, so pruning of conifers should
be judicious.
Don't make large cuts all at once. It is best to
make many smaller cuts than one big mistake,
and don't expect to renovate your plant in
one session. It is better to space your pruning
over a year or two. Removing too much
foliage at once will deprive your plant of its
food-producing source (see page 5, 'How
plants make their own food').
Summer pruning is best to restrict
growth; however, if you wish to invigorate
your tree or shrub, prune in winter
(see 'When to prune', page 26). Usually a mix
of summer and winter pruning works best.
Trees have four main types of aboveground
woody parts: the trunk, scaffold branches,
secondary branches and lateral branches
that hold the flowering/fruiting wood, or
in the case of conifers, the majority of
the foliage.
There are few basic shapes for a tree's canopy.
There are spire-shaped trees with a central
leader or main stem, a rounded crown, or
weeping trees and shrubs such as weeping
roses,
Betula pendula
, silver birch or weeping
willow
Salix babylonica
(see Figure 4.77).
Trees and shrubs with a central leader
Trees with a strong central leader or main
trunk can need the removal of rival leaders.
