Planting a hedge is often the first thing an owner does in a newly inaugurated home. The hedge will delimit the property and protect its intimacy. It can be left free or cut , composed of a single species or an assortment of varieties . Hedges that combine different varieties are very fashionable, as well as being very beautiful from an aesthetic point of view. In fact, the diversity of species makes it possible to host and feed an important and varied fauna . On the other hand, in the event of diseases or a parasitic attack, the mixed hedge, due to its diversity, will be less vulnerable to aggression and will resist better.
Functions and characteristics of hedges
The different functions of a hedge
Purely aesthetic or useful, the function of the hedge in the garden can consist of:
- enclose and delimit the property with hedges that can exceed 2 m in height . The hedge can also be “defensive”, if made up of thorny species.
- Divide the different parts of the garden : vegetable garden, orchard, children’s area or barbecue area, etc.
- Hiding unsightly places : an old shed, a bad wall, an unpleasant view. In this case, plants with a large development will be used.
- Emphasize perspectives , especially in large gardens, or accompany flower beds.
- To represent a protection against prevailing winds , ( windbreak );
- against noise (noise barriers).
According to the function, the species must be chosen, taking into consideration precise criteria: deciduous or persistent foliage , desired final height , decorative flowering , presence of thorns , etc.
Height of the hedges
Most hedges belong to 2 height categories : medium hedges ( up to 2m high ) and high hedges ( ranging from 2 to 6m ). Large trees , used as windbreaks, easily exceed 10 m (even 20 m). There are very low hedges , which do not exceed 1 m in height , also called borders .
Influence of the hedge on the choice of nearby vegetation
The height that is expected of an adult hedge is very important . For example, see the image on the left: when choosing the specimens that can be planted north or south of this hedge, with a west-east orientation , the height will be taken into consideration . This type of hedge projects, towards the north, a shadow equivalent to one and a half times its height , both in spring and in autumn: therefore, specimens must be planted that do not require much exposure to the sun . Instead, south of this hedge, the plants must belong to full sun exposure species, which withstand the summer heat; while it will not be important that they do not tolerate the winter cold or the north wind.
Influence of the type of hedge on the final height
The final height depends largely on the way the trees and shrubs are led . A plantation in which the plants are very close, as happens in hedges, causes, among the specimens that compose it, a strong competition for access to light , water and nutritional elements . This therefore limits its development . For this, attention must be paid to dry soil or, during a year of drought, it must be checked that there is no lack of water . For example, the Carpinus betulus , planted isolated, reaches 20 m in height and 8 m in width . But planted in a dense hedge, that is, 80 cm away from each side, and cut 3 times a year, it will never exceed 4 m in height , it will form a dense avenue of vegetation with shrub rather than arboreal development .
Regulations
The authorized distance between the location of the plantation and the boundary of two properties must be taken into account .
Types of hedges
The free hedges
They are composed of one or several species with different heights . They are formed with deciduous or persistent foliage shrubs . They are generally decorative due to their flowering or fruiting. Pruning is usually very limited or non-existent , precisely in order not to damage this decorative aspect, but also with the aim of maintaining a natural posture (one of the attractive aspects of this type of hedge). They thus assume the typical natural shape of each species of shrub that composes them: some with an erect posture, others with an open posture or with arched branches, sometimes falling down due to the weight of their flowers , etc.
The cut hedges
They are made with species and varieties with deciduous and, above all, persistent or semi-persistent foliage , whose flowering or fruiting is usually not very interesting (for this reason a cut can be performed regularly).
Planting distances are generally shorter than those of free hedges. The cut hedges are shaped according to the taste of the owner, taking into account the characteristics of each species and variety, but also according to the desired height and width criteria for aesthetic or use reasons. There are 3 possible shapes:
- those with rounded tops , the least used;
- those with a rectangular top , the most usual;
- those with a trapezoidal top : the most recommended, especially in coniferous hedges, but infrequent in private gardens. However, they have important qualities: they avoid the widening of the top of the hedge , which is usually produced by the effect of the repeated horizontal cuts of the latter, always carried out at the same level and for years. This form of hedge also allows, in case of heavy snow, a faster fall of the snow . And, moreover, it allows a better illumination of the lower branches , which counteracts the tendency to basal impoverishment in small secondary organs.
The windbreak hedges
Generally they are classified according to height : the small ones (from 5 to 10 m in height ) and the large ones (from 10 to 20 m ). Their function is above all of utility , since they have the purpose, for example, of protecting crops from winds . In this type of hedge there are tree species with different bearing and other shrubs and regularly cut at the base. They consist of the association of plants of 3 different heights , alternating to create a whole resistant to the penetration of part of the wind. It is not recommended that windbreaks are totally impermeable to wind. It is highlighted that a windbreak, small or large, protects crops up to a distance of 6 times its height (i.e., from 50 to 80 m on average when the windbreak is 100% waterproof) or even 10 to 12 times. its height (i.e. 100 or 150 m when it allows only 50% of the wind to penetrate). In this second case, 50% of the wind penetrating the hedge will be on the other side and will oppose the eddies created by the 50% of the remaining wind, which will have risen along the hedge and fall to the ground on the opposite side.
Selection criteria
The plants used in the formation of windbreaks must:
- be suitable for the area;
- quickly reach the desired height;
- to have a rather erect posture, but maintaining a very dense base;
- withstand periodic pruning in their juvenile stage; and then abandon it.
Small windbreaks
They are a set of stump-grown trees and shrubs . A lateral pruning is carried out to limit the thickness of the hedge and reduce its invasion in the cultivation surface . The shrubs have a “filling” role and are planted south of the tree line or interleaved. The trees form the stump starting from bushes (and not from stems), which can be cut at the base periodically.
Large windbreaks
They are sets of tall trees , stump trees (coming from a pruning carried out every 10-15 years) and filling shrubs (these too sprouted from time to time in the stump). Usually the composition is as follows:
- tall tree species;
- species of “stump” raised trees;
- filler shrub species.
The tree-lined bands
They are windbreaks, 2 or 3 times larger than the classic ones and therefore include a greater number of rows of plants. They are used to protect professional crops , repair sports fields, factories, greenhouses, etc. They are not used in confined spaces or in small gardens as they need large spaces. We will not talk about them again.
