Turf Magazine - August, 2008
A valuable part of the landscape
|A formally clipped hedge.
Most landscapes contain a
hedge, or at least some form of one. So, what is a hedge? It depends on how
they are placed in the landscape, but really, they’re just a bunch of
closely spaced plants, usually of the same species and arranged in a linear
fashion. Hedges are not complicated landscape features, but can be a real
eyesore if not cared for properly.
Clients want hedges for several reasons: privacy, to
block views, enframement or simply for something to look at. Hedges provide
an excellent backdrop feature to add another level of layering to a
To avoid pitfalls down the road, take a few minutes to
assess the site. Use a clipboard and paper to sketch out a proposed hedge,
or the existing hedge and surrounding plants.
Use a two-step process for site assessment. First, jot
down facts and observations. Document the soil type, drainage potential,
sun/shade exposure, size of the plants, views from the inside of the house,
driveway and patio, distance to nearby plant materials and hardscape items
and proximity to the property lines and utilities. Second, make a judgement
about why things are the way they are. If the hedge is overrun with
bagworms or mildew, then evaluate the degree of infection and possible
contributing factors. If some stems are lacking leaves, look closer for the
presence of scale or borers.
Look for balance and top heaviness in the hedge.
Because hedges are commonly pruned in a long rectangular shape, they become
distorted in appearance over time. The box shape produced by this approach
causes the lower leaves to be shaded during much of the day. Without
adequate sunlight, they drop their leaves and become bare. In addition, the
plants tend to become wider at the top, because clients prefer that the
lower stems be trimmed to remove the stubbly appearance. Such a hedge needs
to pruned correctly, with the top narrower than the bottom, or to be
Communicate your notes and analysis with the client.
They might be able to offer historical reasons for them, or be totally
unaware of these issues. Either way, a thorough investigation will be of
great benefit. Use these notes and analyses to suggest judicious
applications of pest control agents, removal of sickly plants or
installation of new ones to bolster the planting.
Just like other landscape plants, both low and
high-maintenance approaches can be taken with hedges. Formal hedges and
informal hedges each have their own best applications. Formal ones are
appropriate in (you guessed it) formal settings such as banks,
governor’s mansions and botanical gardens.
A well-cared for and properly sheared formal hedge can
be a glorious landscape feature. They create a regal appearance and provide
a backdrop for shorter plants in the foreground.
The plants that are commonly utilized—privet,
dwarf natal plum, cotoneaster, boxwood, spirea, etc.—require periodic
clipping to keep them well groomed. In northern climes, it is necessary
after a winter period and after each growth spurt, usually three or four
times per year. In southern regions, add a few more shearings to the annual
Informal hedges are low maintenance. They are utilized
in landscapes where a natural look is desired, and are particularly well
suited to the residential landscape. These hedges are generally not
sheared, with pruning taking place only to remove damaged or diseased
An unfortunate third option is not planned, rather it
develops when the landscape begins with a high-maintenance hedge, and
through neglect, it is allowed to become a lower maintenance feature. The
usual scenario is that a hedge is installed with all good intentions of
maintaining it at a high level, but after a short time, the client figures
out the cost of pruning and pest control to properly maintain a hedge and
starts reducing the level of care.
Problems arise when clients think they want a formal
hedge, but have an informal budget or landscape. Be sure to discuss the
maintenance requirements with the customer.
Informal hedges commonly become formal hedges when
they grow to be taller than the client intended. These customers have a
height limit in mind, and when it is exceeded, they reach for the hedge
clippers. This is most regrettable, because once sheared, their low-maintenance informal
hedge automatically turns into a high
maintenance formal hedge. In retrospect, they should have simply chosen a
Choosing plants for hedges
After the site assessment and determination of whether
a formal or informal hedge is best for the landscape, suggest plants that
will match up well with the notes from the site analysis. Be sure to ask
your customer if they have favorite plants or fond memories of ones that
their parents or relatives grew. It’s also good to ask about
preferences with color, fragrance and texture. Fall and winter color are
important considerations as well, especially in the Midwest and Northeast.
If the client drags their feet on plant selection, suggest that they drive
to other parts of town to view other landscapes, and show them
possibilities from your portfolio and Internet sources.
Once the species has been chosen, it must be planted
correctly. Planting may sound simple, but actually can be quite complex.
The species chosen, the type of soil, the desired rate for establishment
and the slope of the land are all important factors when planting. If soil
is drained poorly, plant the shrub slightly above grade. Backfill with
existing native soil rather than amending with compost or peat moss. In
general, space plants one half of their mature width apart; increasing or
decreasing the spacing depending on how fast the hedge is desired to
mature. Flowering types need slightly more room than nonflowering types.
|A close-up of a stem that’s a good candidate for removal.
Another major maintenance consideration for hedges is
pruning. There are four basic categories of pruning:
Formal hedges should be sheared at the beginning of
the growing season to clean up any wayward branches that have gone astray
or become damaged during winter, and then periodically thereafter. The
common yew tends to grow in flushes; rapid expansion of growth in a two to
three-week period of time. Prune these and other formal hedges after each
flush of growth.
|A privacy hedge.
Informal hedges should be pruned once each year.
Summer flowering types should be pruned in early spring, while spring
bloomers should be taken care of soon after the blossoms fade. Remove about
a third of the stems at the ground level to keep the plants thrifty. Choose
the oldest stems for removal.
Old, ratty-looking, deciduous hedges can be renovated
with surprising success if the plants are still alive. A hedge that
contains mostly deadwood or that’s bare of branches at the base and
just a little rough looking at the top should be cut back completely to the
ground and allowed to develop a new top growth system. This should be done
in the spring, preferably shortly after budding and/or leaf expansion
begins. Not all hedge species can tolerate this. Plants that will respond
to this type of rejuvenation are cane-producing types, such as forsythia,
honeysuckle, spirea, lilac, viburnums, burning
bush, buckthorn, dogwood, privet and hydrangea.
Both informal and formal hedges can benefit from
renewal pruning. After five or more years, the stems of many hedges become
thick and woody; as well as attractive to borers, susceptible to fungal
cankers and generally unproductive.
Renewal pruning is a simple and easy way to eliminate
this undesirable growth, and renovate the hedge in the process. It’s
a two-step process:
Remove all stems at ground level.
Pick them up and haul them to a yard waste
A common mistake that is made with renewal pruning is
leaving too much stem to remain, often at the insistence of the client.
Simply put, don’t leave stubs. Doing so will provide possible sites
for canker development and borer invasion.
Because of the drastic nature of renewal pruning,
clients often ask how soon the shrub will look attractive again. Depending
on the growth rate of the shrub species, your client will have a new shrub
again relatively soon; sooner than a new planting. For example, forsythia
will replace the removed stems in just a few months, while burning bush
will usually take a couple of years.
Removal of Knotty Growth
If the hedge is less adversely affected, selective
pruning cuts should be made. The most common pruning procedure of this type
is the removal of knotty growth. Knotty growth results as a consequence of
repeated heading back or shearing cuts made in consecutive years. The
knotty growth generally is found near the periphery of the hedge and is
made up of gnarled sections of stem with many growth directions. To correct
this situation, remove the knotty growth entirely. This may require removal
of 12 inches or more of growth, but certainly not as extensive as with
total rejuvenation. A second step with the lesser type of procedure is to
thin out older, less productive wood on the inside of the shrub.
Unfortunately, evergreen shrub hedges do not respond
well to rejuvenation pruning. As you may know, evergreens tend to be devoid
of growth on the interior as a natural consequence of needles lasting only
between two and four years and naturally senescing. Pine species can be
sheared each June to maintain a tight, dense appearance. Be careful to cut
only the current season’s growth to avoid subsequent defoliation in
following years. Terminal growth should generally be cut in half to allow
for bud set later in the year, which will encourage a tighter, denser
hedge. On pine and especially juniper, new buds will not develop on wood
that lacks foliage towards the center of the shrubs.
Hedges can be a valuable part of the landscape. As a
landscape manager, help your clients choose wisely in terms of species,
pest control and maintenance procedures.
The author is a horticulturist, certified arborist and
frequent contributor to Turf located in Omaha, Neb.