What are Supplemental Support Systems?
Supplemental support systems are hardware systems installed in trees to limit the movement of limbs, codominant stems, and/or entire trees. These systems are used in trees with structural defects, and when used correctly, may extend the life of the tree or reduce the risk of failure. The different support systems include cabling, bracing, guying, and propping, all of which can be used in varying scenarios.
What Scenarios May Require a Supplemental Support System?
The most common structural defect is a tree with codominant stems, with the union of the stems often being considered the weakest point of a healthy tree. The risk of failure is only increased when the union shows signs of decay or included bark. Multi-stemmed trees are prone to failure under the stress of wind or accumulated ice or snow, thus making them hazardous to property or people below.
Another condition with a high chance of failure would be trees with long/overextended branches that grow horizontally or downwards, or have the majority of their foliage towards the end of the branch. These branches can be considered unusually long for the species, and tend to grow beyond the rest of the canopy. Due to how they grow, there is increased tension force on the top side of the branch, which can allow for failure further out on the branch and back to the union at the trunk. Similar to codominant stems, these branches are more prone to failure with snow or ice accumulation, or during a strong wind storm. In addition, a weakly anchored tree could pose a serious hazard. A weak anchor can exist when a tree is improperly planted/transplanted with a poor root ball, roots have been damaged or are decayed, or the tree has been uprooted. In some of these scenarios, a simple pruning can greatly reduce the risk of failure, and is strongly suggested even if a supplemental support system is installed. There are also instances where the necessary location to install a supplemental support system are too weak and/or decayed to support the required hardware. Pruning may mitigate the hazard in these situations, but a full removal may be the best option.
Pros and Cons of Supplemental Support Systems
Cons
The biggest con of installing a supplemental support system is that it is not a fail-safe. Supplemental support systems can only reduce the risk of failure, but they cannot eliminate hazard potential. The only way to completely eliminate hazard potential is to fully remove the tree.
Another con is the financial impact of installing and maintaining support systems. While the initial cost of having a supplemental support system installed may be less than a full removal, it has the potential to add up over time. Routine check ups and maintenance are required to make sure the hardware installed has not worn down, and is still supporting the tree/branches in the way it was intended.
Supplemental support systems are meant to extend the life of a tree, which allows trees to outgrow the hardware that has been installed. Therefore, after a certain amount of time, the hardware should be replaced, further increasing the cost put into the tree, potentially surpassing the costs of removal. Additionally, installation of many hardware systems require holes to be bored through the tree, with the installed systems altering its reactive response to the wind. This could potentially lead to decay forming around the wounds, which in time could lead to failure of the hardware, and failure of the structural defect that the hardware was meant to support.
Pros
As previously mentioned, supplemental support systems cannot eliminate hazard potential, but they can greatly reduce the risk of failure. Additionally, if the hazardous portion of the tree does fail, the hardware installed has the potential to keep it from free falling downwards, lessening the impact or avoiding impact entirely if the tree is above a structure such as a house or shed. Trees are an important fixture to any property, so if an otherwise healthy tree has a structural defect, supplemental support systems should be taken into consideration when weighing the options. Well maintained trees provide financial value to properties, and more mature trees can provide a great deal of shade to homes, in turn lowering energy costs. The older and larger a tree becomes, the more historic value it creates, but it also becomes more challenging to prune. The size of the tree is not the only challenging part an arborist faces, as they are also limited in how much healthy canopy tissue can be removed, meaning that a structural defect may not be able to be fully pruned out without causing further damage and decay. Ideally, it’s best to remove no more than 5-10% of the overall canopy of old or mature trees, whereas young trees can realistically handle having 20-25% of their canopies pruned out. With the added value of an historic tree and the preference of not removing it, as well as the limited ability of pruning it, a supplemental support system is an excellent alternative.
Types of Supplemental Support Systems
Cables
Cables are used to restrict movement between stems with weak unions, or to support heavy/over-extended branches. To provide adequate support, cables are installed approximately ⅔ of the distance between the weak union and the ends of the branches. Cables tend to be difficult to see to the untrained eye due to their relatively small diameter and the height in which they are installed in the tree. There are two types of cable systems, static and dynamic. Static cable systems use steel cables, which arborists have been using for decades to provide support in trees. Dynamic cable systems have been developed as an alternative to static cables, and use a synthetic fiber rope, often made with polypropylene. Static cables are generally believed to provide stronger support, however dynamic cables allow trees to sway more. The tree’s ability to move more freely allows it to produce supporting wood at its weak points, ultimately strengthening the tree over time. Dynamic systems are still relatively new, so information is limited on the effects of UV-light degradation of polypropylene and the overall strength. Ropes in a dynamic system have a splice at the end which wrap around the anchor point before being fed back into the core of the rope. Many arborists feel that the constriction of the rope around the stem or branch that it’s anchored to can have a more harmful impact than that of a static system. Static systems require a hole be bored part way or all the way through the branch or stem where the cable will be anchored. While it is possible for decay to form around the anchor point of a static system, a healthy tree has the ability to heal from, and eventually grow around the installed hardware.
Bracing
Brace rods are used to reduce the risk of two or more stems from spreading further apart. They can also be used to bring back together a union that has already begun splitting. Bracing uses a threaded steel rod that is inserted all the way through the tree, adding support to a weak or weakened union. Unless impractical, brace rods should be used in combination with a cable system, and should not be used as an alternative as cabling alone offers more support than bracing.
Propping
Propping is the installation of a sturdy structure anchored to the ground to provide support for low hanging branches or leaning trunks when cables won’t be as effective. Most commonly, props are used under branches that are nearly horizontal or downward growing to prevent the branch from touching the ground. Props can be made from steel, wood, concrete, or any other material strong enough to support the weight of the branch. Both ends of the prop must be securely anchored to the ground and the branch to prevent failure and the branch falling off. To avoid restricting growth of the branch, a threaded rod is considered the best option for anchoring the prop to the branch.
Guying
Guying is the installation of a cable or cables between a tree and an outside anchor point to provide support and reduce movement. Trees with compromised root balls, whether it be from recently being planted or transplanted to uprooting, are ones that would require guy wires. Guy wires are attached to a tree at or above its midpoint, and anchored to the ground ⅔ the distance to the lowest attachment in the tree. Systems installed on newly planted or small trees should be removed after one year unless the root system is unable to anchor itself. For trees that uprooted or larger transplants, guy wires should remain for three or more years until the root system reestablishes. On mature trees, guy systems may be required permanently as the root system may not be able to reestablish, causing the tree to become dependent on the supplemental support.
Contact the Professionals
When dealing with a hazardous tree on your property, it’s crucial to seek assistance from a licensed tree care professional. Call Barren Tree Solutions today and schedule a free estimate with our ISA Certified Arborist.