In the early days of arboriculture, cement and sometimes bricks were used to fill cavities in hope of providing additional structural support. In fact, pouring concrete in to a cavity was once part of the final exam for the original ‘tree surgery’ schools. Thankfully, we’ve learned that the installation of concrete has no benefit and may even prove detrimental. Today, structural support systems for trees include the use of cables, braces (rods), guys (similar to cables), and props for managing perceived tree defect.
When Do Trees Need Support?
In most instances structural support systems are installed to provide supplemental support between branches and/or branch unions within a tree’s crown. Normally a small branch will grow off a larger branch. Sometimes, however, two almost equally sized limbs will form the trunk of the tree, or be attached to one another in the canopy. This type of structure is the most common cause of tree failure.. Additional defects within trees that may warrant the use of structural support systems include:
* Poor crown architecture
* Branch attachments with included bark
* Cracked branch unions and cracked stems
* Damaged branches
* Over-extended branches
The practice of installing steel cables in trees is a tried and true method that has been around for decades. Traditionally, flexible steel cables are installed in the tree with the use of hardware that is drilled through healthy limbs at an appropriate distance from the branch union. Over time, the tree grows over the cable and hardware at their entry point, making the attachment that much more secure.
‘Dynamic’ cable systems have become more popular over the years, and are a type of synthetic rope that employs a loop and a splice to secure the cable to the tree instead of drilled-in hardware. This is preferred in some situations as there is less initial wounding of the tree, but care must be taken to prevent girdling.
Bracing is the process in which threaded metal rods are installed into the tree to provide additional support to a cable system. Braces are often included in a structural support system to: support cracked branch unions that have included bark, prevent the rubbing of co-dominant stems, and repair cracks within a stem.
Props and Guys
Additional means of tree structural support include props and guys. Guys are often used when transplanting trees in the landscape, but should only be used if the tree requires additional support. Guys (cables or ropes) can also be helpful in up-righting trees, like arborvitae, that have blown over in a storm. Guys are rarely needed for large mature trees.
Props can be helpful with holding the weight of large laterally growing limbs in close proximity to the ground. The Angel Oak of South Carolina is one famous example where props are in place to reduce the chance of branch failure. Props are also installed to help preserve Pennsylvania’s State Champion Mulberry tree, located at Longwood Gardens in Kennett Square, PA.
Careful consideration must be taken when making the decision to install a structural support system within your tree. These systems are an investment, and need to be monitored regularly by a qualified arborist.
If you have any questions about structural support systems, please contact Limbwalker at 502-634-0400.