Le Siepi: When Gardening Becomes Art

In the creation of a garden, hedges are a fundamental, indispensable element, even if they do not reach large dimensions. Hedges cannot be missing both for the practical function they perform and because they enrich it aesthetically: in fact, hedges give the garden a harmony and a style that makes it become a true work of art.

But what is a hedge?

Commonly by hedge we mean plants, especially evergreen ones, grown respecting a very precise geometric shape, obtained by subjecting the hedge to periodic pruning. This concept of hedge, however, is particularly reductive, first of all because there are various types of hedges in relation to the needs they must respond to. In fact, they effectively satisfy a plurality of situations, from the most general ones (defensive, windbreak, etc.) to the specific and particular ones (hiding an unpleasant view both inside and outside that garden). Precisely to satisfy these numerous needs, the choice of species that can be used in the creation of gardens, parks and green areas has greatly expanded and diversified.

Returning to the initial question, the term hedge must be understood in a very broad sense, not only in relation to the function, but also in relation to the very large typology of plants that can be used. These plants can also be very different from each other in size and shape, in being evergreen or deciduous, in the presence or absence of thorns, etc.; even human intervention can manifest itself in different ways: giving the plants a precise shape or leaving them free to grow and assume their own shape.

All these very different plants, with a final shape that can be natural or desired by man, are gathered in the group of hedges because together they form a "barrier", they create a "separation" with linear and vertical development. The hedge must therefore be understood as everything that divides, fractionates or separates. With the words "separation" and "barrier" (a term which especially indicates medium-high hedges) both function and use are clarified; it also explains why this group also includes plants that cannot be grown in shape, such as for example the agave (Agave americana).

Hedges were created to enclose and isolate certain areas, but their function has been enriched with aesthetic meanings, to the point of making them real works of art. In other words, hedges have become the meeting point between man and nature. In fact, man is no longer content to use hedges only on the edges of his property for "defensive" purposes, but has wanted to bring them into the garden, giving them a new purpose and adopting, for the plants used, absolutely original shapes obtained through wonderful pruning interventions, thus giving nature a whole new order and life.

All this should not lead one to think that this type of intervention is violence to the plants, a distortion of nature to achieve the selfish interests of man. Man, on the contrary, has been able to create these works only after a careful knowledge of the biology of plants. In fact, if he wants to give the hedge an unnatural shape, man uses plants whose main characteristic is that of being strongly bushy and particularly tolerant of pruning. Furthermore, continuous pruning strengthens and reinforces the plants, so their branches will be less likely to break.
Man's great interest in these "hedge" plants has not been limited to cultivation care or periodic pruning; he has also selected new varieties, stronger and more resistant to disease but also particularly beautiful to satisfy the needs of every garden.

HEDGE CLASSIFICATIONS 

1) According to human intervention
 a) natural
 b) artificial
 b1) free
 b2) educated

2) According to the function
 a) defensive hedges
 b) ornamental hedges
 c) windbreak hedges

3) According to height 

Hedges have been grouped and classified into some broad categories.
The first of these is based on the way in which human intervention manifests itself in the planting, formation and maintenance of hedges.
The second classification considers the function that the hedge must perform. This classification will include defensive hedges, ornamental hedges, and windbreak hedges.
Finally, hedges can also be classified according to their height. We will thus have woody border hedges, medium-sized hedges and tall hedges or hedges; the latter are exceeded in height only by windbreak hedges.
These last two subdivisions are not based only on the use made by man, but, first of all, on the study of the characteristics of plants; characteristics that are then the basis of their use. However, the use that can be made of a plant is strictly related to the size that plant can reach; in this sense these last two classifications interpenetrate each other. For example, it is clear that a defensive hedge must have an adequate size. These classifications will also give us the possibility of listing and dealing with many species of plants used to constitute the various types of hedges.

1) CLASSIFICATION BASED ON HUMAN INTERVENTION

Hedges can be divided into two large groups: natural and artificial.
The former are mostly free from any human intervention and their origin is always spontaneous, while the latter are created by human will. Artificial hedges can be divided into two subgroups, made up of free hedges and educated hedges.

 a) Natural hedges are those that grow spontaneously in marginal areas of the countryside, left uncultivated by man, such as roadsides, land drainage ditches, or on the borders of the land itself. It is probable that in very ancient times these hedges were left to grow to constitute, with the boundary stones, a very evident sign of the division of property, materially hindering anyone who wanted to access them, and constituting the first example of a "hedge", from which all the others evolved.

These hedges, made up of plants typical of the Mediterranean flora, or which have adapted perfectly to it, multiply easily and can become invasive.

They are often thorny and maintain a deterrent function towards strangers, but they can also be left to grow to consolidate landslide banks, especially if they have a strong root system as in the case of Robinia pseudoacacia. Among these spontaneous plants I remember the blackberry (Rubus fruticosus), the crossthorn (Paliurus spina-christi), the blackthorn (Prunus spinosa), the hawthorns (Crataegus monogyna, oxyacantha) and in southern Italy the prickly pear (Opuntia ficus-indica).

b) Artificial hedges are planted by man according to his own taste and the function they have to perform. Generally this type of hedge is formed by plants of a single species because, if different plants or plants belonging to different species were placed in the same row, a short distance from each other, an unpleasant aesthetic appearance could be created. In fact, for example, the color of the leaves of the common cypress and the oriental thuya differ in shade, and this marked difference stands out particularly, even from a distance, if we place these two plants side by side in a hedge.
Again, an unpleasant effect occurs when deciduous trees, such as Maclura, are planted next to evergreen trees, such as Pyracantha.

It is not advisable to form hedges with plants of different types also for physiological reasons: in fact some plants have a greater growth speed than others. Thus the former, growing more quickly, would alter the harmonious vision of the whole and would certainly occupy the space of the plants with a slower growth rate, to the point of overwhelming them and causing them to succumb. A typical example of plants with different growth rates is given by pittosporum and glossy privet, which must not grow together for this very reason, even if the color of their foliage coincides and would make them associate.

Artificial hedges are divided into free and educated ones.  

b1) In free hedges man limits himself to the planting, after which the plants are free to develop in height and width, without man having to intervene with pruning to contain them. Windbreak hedges fall into this category. Even in gardens we can find free hedges in the form of isolated bushes, formed by plants of modest height.

b2) In educated hedges human intervention is more marked; in fact it is manifested with periodic pruning, aimed at keeping the plants in a certain shape, with interventions of weeding, periodic fertilization, watering during the dry season, anti-parasitic and anti-cryptogamic treatments if the animal attack or fungal infection is so serious as to compromise the aesthetics and/or the survival of the plants. This group includes all cultivated hedges, even if they have different functions such as defensive ones, those for borders, etc., which will be discussed later. 

2) CLASSIFICATION BASED ON THE FUNCTION THAT THE HEDGE MUST PERFORM 

The functions that hedges must perform are essentially two: that of fencing and that of decorating; each of these two functions is performed by different plants with different characteristics. In some areas particularly beaten by the wind, the need has arisen to place high protective barriers; this barrier is called windbreak.

a) DEFENSIVE HEDGES 

The oldest function is certainly that of fencing a private area, to prevent the entry of strangers. Hedges that perform this function are defined as "defensive". For this function, plants that have strong thorns have been chosen, such as the Maclura aurantiaca. This plant does not belong to the Italian flora but has adapted well to the Mediterranean climate, and is often used for defensive purposes due to the presence of strong thorns and its rusticity. Another plant used for defensive purposes is certainly the Pyracantha, an evergreen, rustic plant and obviously with thorny branches.

This plant also has a certain ornamental value because, if grown in a natural shape, it produces very decorative red berries that remain on the plant from September to March; if it is grown in a forced shape, that is, subject to frequent pruning, the production of berries will be much lower. Crataegus are also used to create defensive hedges, but also for ornamental purposes since they have very decorative flowers and small reddish fruits that remain on the plant even in winter. The European hawthorn (Crataegus oxyacantha) belongs to this genus of plants. It is a rustic, deciduous plant, and obviously with thorny branches, which resists well to the fumes and gases of the urban environment, and therefore lends itself to being grown even in the city.

b) ORNAMENTAL HEDGES

Hedges also have another function, the ornamental one; these hedges are created only for aesthetic use. We can say that hedges are the pen stroke of the landscape architect. In fact, the land where the hedge will be built can be considered as a hypothetical white sheet on which the hedges will draw, for example, long green corridors to divide the garden into several sectors, within which there could be other hedges to delimit the flowerbeds, making the design more evident. The flowerbeds could be isolated and unique, forming for example large flat geometric figures, or they could be symmetrical with respect to other flowerbeds, etc. The flowerbeds could be used as tiles in a mosaic: the set of their designs could give life to a new and complex figure.
Hedges can be designed to guide the eye to particularly valuable areas of the garden, as happens, for example, when in the center of the garden there is a fountain with water features, which, due to its position and beauty, has been designated as the most important point of the garden. The human eye will be guided towards it by the paths bordered by hedges, which will start from various points of the garden to all converge towards the fountain.

The hedges that design a garden are necessarily formed by small plants, so that the eye can easily grasp the interweaving of the lines, the geometries and therefore the overall effect. Hedges can also become the element of "closing" the garden: in this sense the hedges surround the garden not to prevent access to strangers but to prevent the gaze from "leaving" the garden and getting lost.
These hedges are necessarily larger than the previous ones, so they are made with different plants with higher development. They can be considered the ideal frame of the garden. Hedges also give to a small garden that regularity, that geometric order, which constitutes the right combination between art and nature.
Ornamental hedges should not be understood only as games of lines, symmetries and flat geometric figures; in this sense, solid figures, both geometric and non-geometric, should also be included. Wonderful prunings have transformed plants into three-dimensional figures that give the garden a fantastic and classic look at the same time. The creation of solid figures using plants has given rise to a true art: topiary art.

Gamberaia Villa Garden – Parterre – Settignano Florence

The most used plant to obtain “flat geometries” is undoubtedly boxwood (Buxus sempervirens). This species of boxwood is a plant that has a very slow growth rate, it never reaches large dimensions and for these two reasons it is very suitable for forming ornamental hedges of modest dimensions, such as those found at the edges of flowerbeds or that border paths or driveways. Boxwood is also widely used because, thanks to periodic pruning, it takes on a very compact shape and is thornless. In fact, it plays a leading role in the history of Italian gardens.   

Among the plants that can be used to frame the garden to form solid figures I remember the yew, the holm oak and the cypress.
The plants to be used to create these types of ornamental hedges must always be chosen from those of the Italian flora such as, in fact, boxwood, laurel (Laurus nobilis), yew (Taxus baccata), holm oak (Quercus ilex) etc. 

c) THE WINDBREAKS

Plants that can be used to form windbreaks must have certain characteristics. These are: rapid growth, compactness, elasticity and height. Height, together with elasticity, is certainly a very important quality, because the extent of the coverage offered by the windbreak depends on it. In fact, the protected area is equal to ten times the height of the windbreak. This function is performed more by rows of trees than by actual hedges. A fairly common windbreak is made up of rows of Italian cypress (Cupressus sempervirens). This plant has a compact crown, good height and above all a fair amount of elasticity, a basic characteristic for resisting even the strongest winds.

The Italian cypress can also be used to create tall hedges because, like many species of cypress, it tolerates pruning quite well. Many other plants of the Cupressaceae family are used to create tall hedges or barriers; among these, the Leyland cypress (Cupressocyparis X Leylandii) stands out. This plant is particularly rustic, very resistant to pruning and indifferent to any type of soil. Furthermore, among its peculiarities there is a high speed of growth.

We can also mention the Monterey cypress (Cupressus macrocarpa) as a windbreak tree, which is used especially in coastal areas for its resistance to salty winds.

In marine areas, the Eucalyptus is equally widespread as a windbreak tree, both for its rapid growth, for its resistance to salty winds and, above all, because near the sea the temperature remains mild, an essential aspect for this species, which cannot tolerate excessively intense cold.

In many areas of Italy, it is common to use the cypress poplar, which is a very common variety of black poplar, to create windbreaks. This plant is called the “cypress” poplar because it has a columnar shape, branches very close to the trunk and therefore a very compact crown, reminiscent of the common cypress. It also has in common with the cypress the flexibility of the trunk and a fair height. The cypress poplar is a fast-growing plant that thrives and develops especially in constantly humid areas.

3) CLASSIFICATION BASED ON THE HEIGHT OF THE HEDGES 

A further subdivision of hedges is based on the height of the hedges themselves: low or decorative hedges and tall hedges or hedges. In reality, when hedges do not reach forty centimeters in height, we should more precisely speak of a woody border. Woody borders are made up of plants that do not reach great heights in themselves, such as boxwood, and must only fulfill an ornamental function. The difference between woody borders and hedges of modest or medium height, on the one hand, and tall hedges or hedges, on the other, lies in the fact that the former allow the observer to overlook them, given their modest height, while the latter have the task of closing the view of what is present "beyond".

Among the most commonly used species to create woody borders we can mention Mahonia, Berberis thumbergi atroporpurea, spindle (Evonymus), lavender (Lavandula), Santolina chamaecyparissus, thyme (Thymus vulgaris), etc.

Tall hedges are made up of plants that in nature have a growth habit of several metres, such as the holm oak (Quercus Ilex), which easily reaches 20-25 metres in height with a crown diameter that can reach 15 metres.

Given these characteristics, it is obvious that it will be used for large hedges that can reach 6-8 metres or more, or to form isolated solid geometric figures such as truncated cones or spherical ones, which are always dimensionally significant.

Among the plants that are often used to create this type of hedge, the most notable are: cypress and cherry laurel (Prunus laurocerasus). This last plant is widely cultivated in urban areas because it tolerates polluted environments.

The cherry laurel grows quickly and is used for hedges that can reach and exceed 3-4 meters in height. The cherry laurel, like the holm oak and the cypress, is an evergreen plant. With these plants you can create hedges that have ornamental value: for example, with them you can create real green walls at the edges of the garden, to frame the garden itself, or you can create large isolated figures. However, to obtain these effects you need a large garden, and suitable means to reach the top of the plants.

Hedges: When Gardening Becomes Art (Part 2)
Hedges: When Gardening Becomes Art (Part 3)
Hedges: When Gardening Becomes Art (Part 4)

BIBLIOGRAPHICAL REFERENCES 
– AA.VV. “THE GREAT BOOK OF FLOWERS AND PLANTS” Selection from Reader's Digest – Milan – 1978
– E.Susini “MY FLOWERS AND MY GARDEN” Edagricole 1987
– E. Susini “HEDGES AND BORDERS” Edagricole
– E. Susini “GUIDE TO DESIGNING SMALL GARDENS” Edagricole
– MGBellardi “WHITE DISEASE ON CHESTYLAURE” From “GIARDINI” May 2005
– M.Ferrari “LIMANTRIA OR ODD BOMBYX” From “GIARDINI” May 2005
– M.Ferrari, A.Menta, E.Marcon, A.Montermini “DISEASES AND PARASITES OF FLOWERING, ORNAMENTAL AND FORESTRY PLANTS” Edagricole
– M.Ferrari, D. Medici “TREES AND SHRUBS IN ITALY – recognition manual” Edagricole 2003
– L.Crespi “BONSAI – practical guide to art and cultivation” Fabbri editors 1989
– G.Oelker “FLORICULTURE MANUAL” Edagricole 1957

Paolo Pecchioli, Agrotechnician, holds a qualification diploma as a horticulturalist. He currently holds the position of Technical Assistant at the Agricultural Technical Institute of Florence.

USEFUL LINKS

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http://it.wikipedia.org/wiki/Siepe
http://www.rivistadiagraria.org 
http://www.giardinaggio.it/speciali/Siepe/Siepe.asp
http://www.vivaioclorofilla.it/html/giardini_isegreti.htm