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Hedges

A valuable part of the landscape
By John C. Fech


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 landscape.

Site assessment

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 renewed completely.

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.

Formal hedges

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 total.

Informal hedges

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 stems.

Third option

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 shorter species.

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.

Pruning

Another major maintenance consideration for hedges is pruning. There are four basic categories of pruning:

Annual 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.

Renewal Pruning

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:

  1. Remove all stems at ground level.
  2. Pick them up and haul them to a yard waste recycler.

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.

Evergreen Pruning

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.