Of
the many gardening tasks, few are as daunting to beginners as pruning
shrubs and trees. Having invested considerable time and money in
these plants, we are understandably hesitant to start lopping pieces
off of them. Have courage. Following a few basic principles, guided
by an understanding of the reasons for pruning and the consequences
of doing so, anyone can prune successfully. In
this article, we'll introduce the basics of pruning trees and shrubs,
outlining tools and techniques that will provide a sound foundation
for developing pruning know-how.
WHY
PRUNE?-
Gardeners prune for two reasons: to maintain and enhance a plant's
health, and to affect the extent and form of its growth. Health-related
pruning is, for the most part, straightforward and commonsensical.
Branches and stems die naturally. Some contract diseases or are
damaged by pests; others are damaged by snow, wind, or excited children.
Removing these improves both health and appearance. Sometimes plants
grow too densely and require thinning to admit light and air. Drastic
pruning can reinvigorate certain plants that have grown old and
tired.
The
second category of pruning is more subjective--your idea of an attractively
shaped shrub and your neighbor's may differ completely. Some people
train, trim, and shear shrubs and trees into all sorts of shapes.
Others try to maintain or enhance the shape nature provides. Both
types will have occasion to prune to encourage bushy or compact
growth or to direct a branch into an area.
Too
often gardeners spend hours pruning to maintain plants that are
in the wrong place. Any older neighborhood yields examples of shrubs
and trees grown over windows, crowding foundations, or towering
over their surroundings. Examples of sun-loving plants struggling
in the shade, or vice versa, are also common. You can avoid long-term
pruning headaches by choosing trees and shrubs carefully. Select
plants whose mature size fits their site. Match the conditions of
the site with the plant's preferences for sun, soil, and moisture.
To
a novice, pruning may appear to be a purely reductive activity,
the point of which is to end up with less than you had. While this
is sometimes true, much pruning is in fact done to encourage growth.
A little plant physiology will help you understand how this is possible,
and help you to anticipate the consequences of the pruning cuts
you make.
All
plants produce growth hormones, called auxins, in the tips of growing
shoots. Auxins stimulate growth at the tip and suppress it along
the sides of the shoot. Removing the growing tip and its supply
of auxins releases some of the buds along the shoot, called lateral
buds, from dormancy, allowing them to form side shoots. Although
the strength of auxins varies among plants, in general, pruning
that removes a growing tip will induce growth on the shoot, stem,
or branch that remains.
(Some
conifers junipers, arborvitae, hemlocks, and many pines-won't generate
new growth if cut back to wood that is too old.)
Much
of the pruning we do enlists this phenomenon. We shear yew or privet
to create a dense hedge; we head-back roses to outward-facing buds
to stimulate an open framework of lateral canes. Sometimes the consequences
of such pruning are unintended attempts to shape a forsythia or
spirea may result in an awkward thicket of lateral shoots. Think
before you prune.
