Landscape & Urban Design Issue 18 2016 | Page 61

Supporting with ropes Supporting trees with any kind of cable or rope needs a lot of space and can create pitfalls. They are totally unacceptable in pedestrian areas Static anchorage There are anchorage systems on the market which use steel cables and ground anchors made of an aluminum wedge. The system is installed by hammering it into the earth with a peg, then fastening it with a ratchet to tighten the cable. Using this type of system the tree is stiff and rigidly anchored as if they were supported by stakes. Naturally this has the same disadvantages. This system also has the problem that if the trees stem thickness increases, it tightens the cables which then depress the cambiums, resulting in grooving, especially if the fastening is done by a sling. Dynamic anchorage The advantage of this type of anchorage is its suitability for the natural growth of the tree. The tree can sway freely and grow strong. However systems with screw in anchors require exact placing and adjustment. To install the anchors you must operate outside the planting hole, which can cause problems when setting because of obstruction by stones. There are other systems which use shock absorbers or soft synthetic ropes. These are rather problematic because of the synthetic materials and its vulnerability to vandalism. A knife or pocket lighter is enough to severely damage the support and consequently the tree. The relative movement of the bale within the planting hole is not completely eliminated. On lawns, there is also the possibility of damage my mowers by a circular knife which results in a spherical bale. The bale is immediately covered with a jute bale cloth, which is secured in wire netting. In its new planting hole, it would obviously stand like a ball in a socket. A sphere has no resistance to turning, so this has to be prevented in its new location. Some trees naturally grow tap roots; therefore it makes common sense to employ this principle when replanting trees. A new system has been developed taking into account this principle. Arbofix was first introduced at the GaLaBau exhibition in Nürnburg Germany, and was immediately awarded the coveted award for innovation. It is produced in four sizes to accommodate different diameters of stem. Arbofix is fitted with only 3 blows of a mallet through the central ring of the wire netting. The system works well with densely rooted bales without damaging the roots. The practical proof of this system was demonstrated after hurricane Kyrill which occurred on 18th January 2007 Twenty one newly planted acer plantenoids with stems of 18cm – 20cm had been planted in a relatively light substratum using the Arbofix securing system. The planting site was not completed, and the trees were standing on steep sided molehills made of the substratum. The trees were not supported on the sides by the planting holes. Despite the severe hurricane force winds, no tree was unearthed or even pushed over. The planting site was an unprotected high plateau in the black forest. Several other healthy trees which had been planted on the same site with other systems overturned or were badly damaged. This clearly showed the benefits of the Arborfix system. Underground securing All underground securing systems avoid any visual interference and are aesthetically more pleasing. The trees can grow unmolested, because there is no interference to the natural sway and therefore with the hormonal interdependency, allowing the tree to develop to its optimum potential. Bale pressing using aluminum earth anchors and tensioning ropes By using polyester slings and aluminum anchors, non rotting materials are inserted into the ground, which is not really satisfactory. With this type of system, attention also has to be paid to the possible compression of the roots. Uninterrupted root growth can only happen where there is no sling, consequently, after the tree’s roots have struck, the polyester slings and ropes must be taken out and disposed of. Bale pressing using wood This system has advantages and disadvantages. The disadvantage is that the system uses force on the bales by pressing them which is not good for root growth. The advantage is that the wood will totally decay. However, this takes longer than it takes for the tree to be standing securely. Bale interlocking This systems development started with consideration right from the start of the extraction of the tree at the nursery. The tree is taken from ground Overview of plant securing systems Commercial landscape gardening companies work in a very competitive market place. Contracts are won and lost on price alone leaving narrow m \