Horticulture Principles and Practices

3. Number of wounds. A plant with few wounds heals more quickly than one with
numerous wounds.
4. Species. Relatively longer-lived trees such as oaks tend to heal more quickly than
short-lived trees such as willows.
5. Age of plant and plant vigor. Younger plants have more vitality and thus heal
more quickly than older plants. Further, when buds and leaves on a plant are
expanding, wounds tend to heal slowly because plant energies at that stage are
channelled into growth activities.
6. Environmental conditions. Temperature and moisture conditions play a role in the
healing process of wounds. Early spring provides the best conditions for wound
closure; wounds heal slowly in late fall and early winter when physiological
processes slow down.
7. Use of wound paint. Wounds used to be treated with pesticides and other chemicals
believed to prevent or slow the rate of rotting. Wood paints included asphalt-based
dressings, antibacterial preparations, and fungicides. The use of wound paint is a
thing of the past. When rotting occurs to the extent that cavities are formed in the tree
trunk, such holes may be plugged with materials such as concrete, asphalt, and
polyurethane foam. These wound treatments may actually seal in the pathogens and
promote disease.
19.5.4 WHEN TO PRUNE
Pruning may be done during or after the dormant season when flowering occurs. On
certain occasions, plants are pruned during both the dormant and active seasons.
Species differ regarding the best time to prune them. For the same species, pruning may
be done at different times during phases of plant growth and according to the production
schedule. Species that flower in spring (e.g., lilac, forsythia, and magnolia) develop
flower buds during the previous growing season. Such species are pruned after flowering.
On the other hand, species that flower in summer or fall (e.g., rose, croton, blueberry,
and dogwood) develop flower buds in the current season’s growth (i.e., on the
new growth). As such, it is best to prune them before the new growth begins in spring.
Spreader Board
A flat piece of board with
V-cuts at both ends that is
forced between the stem
and a branch with a
narrow crutch to widen it.
19.5.5 WHEN CUTTING IS NOT DESIRABLE
Pruning involves cutting plant parts. Some plants (such as pears) tend to develop a
narrow profile such that the branches do not spread but grow upright, nearly parallel to
the stem. In such situations, removing a branch might do more harm than good in terms
of productivity. A solution to this problem is to open up the canopy by inserting boards
(spreader boards or branch spreaders) between adjacent upright limbs to push them
apart (Figure 19–7).
FIGURE 19–7 A spreader
board may be used to open up
the canopy of a tree for the
development of strong and wide
crotches.
Narrow branch
angle
Wide branch
angle
Spreader board
576 Chapter 19 Pruning