• Site Assessment • Site Preparation & Establishment • Design Pointers
• Clipping Theory • Clipping Tools • Clipping Technique • Simple Shapes
• Complex Shapes & Figures • Problem Solving • Growing Topiary

• Clipping Theory

Introduction
When trees and shrubs are allowed to grow naturally, without intervention from shears or clippers, then a loose natural shape or form is the result.
The plant puts all its energies into filling new vacant areas of sky,
growing upward and outward to produce each species characteristic and
natural airy shape.

This, although beautiful, is not what we require when we make use of these plants within the sculptural art form of topiary. Here we are seeking to control the growth, to form from it the shapes we desire. Also to control the extent of growth annually in order to maintain those shapes once we have achieved them. We seek too, to increase the surface density of our pieces - to promote a very even and close finish on the exterior and hopefully a strong and relatively rigid structure beneath.

All this is achieved through the clipping operations we carry out - the main human physical intervention that we undertake in our craft.

The Underlying Science

As for the basic physiological reaction of the plant - in normal growth
conditions, the apical or end shoots are producing growth hormones that
suppress the development of the side growth buds immediately below them. In all plant¹s leaf axils - that is where leaf joins stem - a bud rests which has the potential to develop into a new shoot. Most of the time however, these buds remain dormant as all energy goes into extension growth at the tip of the main shoot.

In unclipped trees and shrubs at the end of the growing season, shoots
produce terminal resting buds and after over-wintering these will break and a further single long extension shoot will develop. There will be some side shoots further back along the twigs where the suppressing effect of the leader growth¹s hormonal activity is diminishing.

When we clip or trim these shoots however, then the terminal bud is removed and with it, its flow of hormone that has been suppressing the growth of the axillary buds. The result is a great multiplication of side growths at a lower level.
Repeated trimming once again removes all new apical buds, further
encouraging in filling. And as each time we trim, we cut back to nearly the same plane, then the result is a surface of very densely packed growth.
This is the ultimate tight, close textured, leafy surface we are trying to achieve for our topiary sculptures.

Timing
The subject is timing is one for great debate amongst gardeners over many operations, and on the subject of clipping in particular. It may be true that there is an optimum time for each operation, but it is also true that practically every gardening operation can equally well be attempted on an opportunistic basis. ŒCorrect¹ timings may be used as guides, but often in real life the time to do the job is when opportunity, inspiration and enthusiasm conspire to make then, now!
Here, we will discuss the reasoning behind the when to and that behind the when not to...
With most species used for topiary and in most climatic zones, there are definite seasons of growth (spring and summer) and a dormant period
(autumn/fall and winter). Aesthetically, our topiary pieces look best when trimmed back to the tight lines of their allotted forms. That is they look really good just after their trim and before fresh new growth blurs the outlines of the shapes once more.



Timing of their trim can thus be used to maintain the pieces at optimum
sharpness of outline for the longest period by cutting the growth off at the end of the growing season. This is the technique used most often in large collections where it is possible only to do a maintenance cut of each piece
once a year. In UK conditions most clipping work is tackled in late summer.
This then gives the longest period of time - right round until the following May/June in which to view and enjoy the tightly clipped shapes.

When labour exceeds work, where perfect results are necessary at all times and also when topiary is still in its formative stages, then clipping more than once each year will provide the best results. This may be particularly necessary where the species used is very vigorous in growth thus continually blurring outlines without our intervention, or when very finely detailed features need to be maintained, or when seasonal weather variation is slight and active growth continues the year round.
In these cases, trimming may be required every four to six weeks and
although obviously time consuming, this kind of treatment will lead to a far finer finish, much sooner on new pieces and a tighter more controlled surface on established specimens.
As for when not to clip, then we would normally beware of trimming in
adverse weather conditions. In the UK in particular we would normally
choose not to trim during severely cold, frosty conditions. Box - one of the mainstays of the topiary tradition here - can be severely damaged if cut during icy periods. With this species it is traditional to trim after the last possibility of night radiation frost has passed - normally at the end of May/beginning of June. Any new growth made thereafter has time to harden sufficiently before cold conditions return in the Winter.



Clipping rules can be bent slightly by clipping through the Autumn, and in to early Winter. This is through necessity rather than choice, as we unfortunately only have the staff available at this time to do the work.
Generally speaking though, only minor damage has occurred through the
scorching of cut box during particularly frosty conditions.
Given the choice, clipping earlier would be better. It is however also a mistake to clip Box too early. Many are tempted by good Spring weather to trim in April. Unfortunately the plants are immediately prompted to produce fresh growth which is often killed or severely damaged by hard late Spring frosts during May. Clipping too late in the growing season also prompts the dangerous production of tender new shoots. Old box growth however, is of course relatively hardy.



Yew, that other great mainstay of our topiary tradition, can also be clipped more than once a year for a tighter, more controlled effect. Here a trim of the first big flush of new growth can take place in July. A second tidying cut to any new shoots produced is undertaken in September. With this species, if a single trim a year is made, then any time after the end of August will do, but preferably before the worst Winter conditions begin. Early, rather than later clipping, should always be our aim.
Lonicera nitida and Privet Ligustrum species are such vigorous growers as to need repeated trimming during the growing season. While Beech Fagus silvatica and Hornbeam Carpinus betulus require only a single trim from late August to keep neat. Their golden Autumn/Fall foliage should be retained through much of the Winter to enhance their decorative effect.



Holly Ilex aquifolium and some other large leaved evergreens are often
trimmed in late Spring and perhaps again in late Summer. These species
often have very large leaves which may look unsightly if trimmed using hedge clippers. They therefore are often tackled more slowly, removing individual shoots with secateaurs. This certainly takes time, but the results usually justify this approach if the specimens come in for close scrutiny.

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