Save mature trees from the bulldozer when sub-dividing

Press, 9 April 1981, Page 14

Save mature trees from the bulldozer when sub-dividing

LANDSCAPING YOUR HOME

Gilbert Brakey

In recent years many larger Christchurch sections have been subdivided into smaller and more manageable sizes. Subdivision applies particularly in areas containing examples of fine established gardens, where trees and shrubs are well matured and in many .cases at their peak in appearances. This may be an unfortunate aspect of our times, but the over-all effect of these heavily planted areas does not need to be des-, troyed in order to subdivide, and build new houses or commercial complexes. It does mean, however that our ideas must change quite dramatically. We need better knowledge in order to understand what is required to protect the character of an area. . Mature trees and shrubs are possibly the most important heritage a landowner can have, and every effort should be made to protect them. This does not mean, however, that selective removal should not take place. Often existing gardens can be overgrown. seedling trees spring up in undesirable places, and shurbs can be old and past their useful life. However, it can well pay to use the knowledge of a qualified landscape architect to decide what should be removed, and what should stay. The positioning of new buildings should be carefully carried out to ensure only the minimum of removal occurs. The building shoudl be designed to incorporate the trees in particular as part of the over-all design. If a tree is in the way of a wall, relocate the wall if at all possible. Usually it is possible.

Remember, even a small tree may represent ten years's growth, and a mature hardwood could well be reaching a TOO years of age. although the majority of our mature Christchurch trees are around 70 years of age. Just a few axe blows, a couple of minutes with a chain saw can undo the work of years. Even if a tree appears diseased or unstable, seek the advice of a trained tree surgeon or landscape architect. Local councils who have trained staff are always interested in the more significant trees, and it is possible have your tree officially placed on a protected list. Today most people are conscious of the value of trees, and not many will wantonly destroy one. However, unthinking neglect or alterations to the surrounding environment can surely kill mature trees as if they were to be chopped down. During numerous years a tree or shrub adapts to a particular set of site conditons and will in turn contribute to a well balanced mircoclimate. A plant’s health may be upset by such rough treatment as cutting back its roots or branches. There are less obvious actions that are potentially damaging, such as changing the soil level around a tree’s trunk, or even removing the plants surrounding a tree. The careless use of mechanical eqipment, tools and materials can cause damage to a tree or shrub and any damage can permit the entry of insects, borers or water borne diseases. To prevent such damge the plants should be effectively fenced off. Where damage does occur care should be taken to clean the wound and seal it with a suitable sealing compound (not ordinary paint). It is best not to interfere with the roots, of a tree at all. If some cutting is unavoidable due to nearby construction, roots any thicker than 75mm should be left and others sealed immediately after cutting. Where roots are temporarily exposed, they should be kept moist by wrapping them in damp hessian. As a general rule no more than five per cent of a tree's roots sould be removed. When a sloping site is

being levelled it may be necessary to change* the height of the ground around a tree. Levelling may be by digging out or filling in. Many trees have their feeder roots close to the surface, and if soil is to be added the roots will be deprived of essential oxygen and subsequent die back will occur. If excavation works are carried out feeder roots may be damaged or exposed to the open air and cease to function. Trees develop feeder roots at the "drip line” of the trees canopy due . mainly to the fact that more rain falls outside of the trees’ canopy than under its protective umbrella. To maintain the soil levpl within reach of these roots ■ when exacavating around a tree means retaining a wide raised or lowered

platform and there are several ways in which this can be achieved. Incidentally, the Christchurch City Council produces a worthwhile booklet dealing with the methods of tree protection, should you require information. In a tree’s natural state it is unusual to find it growing on its own. Normally it forms part of a larger group of trees and shrubs, graded in size to provide effective resistance to the prevailing winds. The removal of surrounding growth which occurs in an established garden will change the mocroclimate to which a plant has adapted and as a result it may deteriorate in health. For the most effective protection plants, both trees and

shrubs should be fenced off against damage. Maximum spaces and clearances should be catered for to ensure a successful

survival of all existing trees and shrubs. These can be then utilised in a subdivided area to produce an immediate and much sought after mature garden surround.